Physiology - Quesions - Block 3 - (Renal - uWORLD)

The following measurements were taken from a healthy 33 y/o volunteer: PAH urine: 100 mg.ml; PAH serum 0.2 mg/ml. Assuming a hematocrit of 50% and a urine flow of 1 ml/min, which of the following is the beset estimate of the patient's renal blood flow?

1000 ml/min Remember RBF = (Urine[PAH]* Urine flow rate)/ plasma [PAH] RBF = (RBF) / (1 - hematocrit)

A longitudinal study is conducted to assess changes in renal function over time in patient with recently diagnosed type 2 DM. An initial set of laboratory tests is obtained in newly enrolled patients to establish baseline renal function parameters. The following measurements are taken from a 42 yo male volunteer. Creatinine Urine: 110 Creatinine Serum: 1.1 PAH urine: 100 PAH serum: 0.2 Which of the following is the best estimate of the filtration fraction in this patient assuming a urine flow of 1.0?

20% > FF = GFR/RPF GFR = [Creatinine Urine][Urine flow rate]/ (Plasma) - Use creatinine RPF = [PAH urine] [Urine flow rate]/ (Plasma) - Use PAH

Substance A is freely filtered in the glomeruli and reabsorbed in the renal tubules. A healthy volunteer receiving substance A has the following findings: Inulin Clearance: 100 mL/min PAH Clearance: 500 mL/min Plasma concentration of substance A: 0.5 mg/Ml Tubular reabsorption of substance A: 25 mg/min What is the expected excretion rate for substance A in this volunteer?

25 mg/mL Filtration = (GFR) (Plasma Concentration of Substance A) Reabsorption = (25 m mg/min) = 100(0.5) - 25

A 25 yo old African American man comes to the office with a 1 month history of increased abdominal girth and swollen extremities. His BMI is 32. Laboratory evaluation shows-decreased serum albumin and hypercholesterolemia. Urinalysis reveals heavy proteinuria and fatty casts. A renal biopsy shows findings consistent with focal segmental glomeruloscerosis. Despite aggressive medical management, the patient requires a kidney transplant from his younger sister, who is a 5 out of 6 HLA antigen match. As a part of his post-transplant immunosuppressive regimen, he takes a medication that inhibits lymphocyte proliferation by blocking interleukin-2 single transaction. The emaciation used by the patient is most similar to which of the following drugs? Bortezomib Mycophenolate Prednisone Rituximab Sirolimus

> Sirolimus This patient developed nephrotic syndrome due to focal segmental glomerlosclerosis (FSGS). Risk factors for FSGS include African American ethnicity, obesity, drugs (eg. heorin, anabolic steroids), and viruses (eg. hepatitis, HIV). FSGS can cause progressive renal failure and eventual ESRD, requiring treatment with dialysis or renal transplantation. Siroliimus bind to the immunophilin FK-598 binding protein (FKBP) in the cytoplasm, forming a complex that binds and inbihits mTOR. Inhibition of mTOR signaling blocks interleukin-2 signal transduction and prevents cell cycle progression and lymphocyte proliferation.

Aminoglycoside antibiotics accumulate within the renal cortex causing _________________

Acute tubular necrosis

______________, an anti-CD52 humanized monoclonal antibody, is used for treatment of chronic lymphocytic leukemia.

Alemtuzumab On binding to CD52, alemtuzumab imitates a direct cytoxic effect through complement fixation and antibody-dependent, cell-mediated cytotoxicity.

A 26 yo previously health man comes to the office with a 3 week history of SOB, cough, hemoptysis preceded by a upper respiratory tract infection. He has no fever, night sweats, or weight loss. His BP is 150/85 and pulse is 86 and regular. Physical examination reveals bilateral inspiratory crackles and lower extremity edema. His creatinine is 4.1. Urinalysis shows proteinuria and hematuria with dysmorphric RBCs. Bilateral pulmonary infiltrates are seen on chest x-ray. He is also found to have an increase CO diffusing capacity (DLCO) on pulmonary function testing. Antibodies directed against which of the follows is most likely to be assisted with this patient's condition? Alpha 3 chain of type IV collagen Beta-hemolytic streptococci Cadiolipin phosphoplipid Double-stranded DNA Topoisomerase I

Alpha 3 chain of type IV collagen > Goodpasture syndrome is caused by autoantibodies against the alpha 3 chain of type IV collagen in glomerular and alveolar basement membranes (anti-GBM antibodies). Patients typically present with rapidly progressive glomerulopneprhitis (nephritic syndrome) and alveolar hemorrhage (SOB, hemoptysis)

______________ is an inherited condition the results in early emphysema and liver cirrhosis

Alpha-1 antitrypsin defiency

A 57 yo man with autosomal dominant polycystic kidney disease develops ESRD and undergoes renal allograft transplantation. During the operation, the surgeon notices that the graft becomes cyanotic and mottled soon after its blood vessels are connected with those of the recipient. Blood flow to the graft ceases and no urine is produced. Which of the following immunologic mechanisms best explains the finding observed by the surgeon? Antibody-mediated hypersensitivity Cell-Mediated hypersensitivity Graft-Virus-Host disease Immediate hypersensitivity Immune complex-mediated damage

Antibody-mediated hypersensitivity > Hyperacute rejection is mediated by performed anti-donor antibodies in the recipient that attack the transplanted organ (type II hypersensitivity). Examples include anti-ABO and anti-HLA antibodies. This form of rejection occurs immediately upon intimal perfusion o

A 44 yo man who was recently diagnosed with idiopathic membranous nephropathy after developing edema comes to the office due to a sudden onset of left flank pain and gross hematuria. The patient has no other medical problems. He is taking furosemide and ramipril. Blood pressure is 135/85 and pulse is 88. On examination, there is left flank tenderness. The patient's edema has improved from the previous visit. There is a left-sided varicocele that the patient has not noticed before. Urinalysis shows increased proteinuria and new hematuria. Serum lactate dehydrogenase is elevated. unitary loss of which substance most likely predisposed this patient to his acute condition? Albumin Alpha-1 antitrypsin Antithrombin II Ceruloplasmin Immunoglobulins Lipoproteins

Antithrombin III Nephrotic syndrome is a hypercoaguable state. Sudden-onset abdominal or flank pain, hematuria, and left-sided varicoceles suggest renal vein thrombosis, a well-known complication of nephrotic syndrome. Loss of anticoagulant factors, especially antithrombin III, is responsible for thrombotic and thromboembolic complications of nephrotic syndrome

A 34 yo woman comes to the physician complaining of frequent urination. She has tried limiting her fluid intake but found it difficult because she got very thirsty. The physican assess the water-conserving function of her kidney by performing a water restriction test, which shows inappropriately dilute urine. lab studies drawn during the period of water deprivation show low vasopressin levels. The physician diagnoses the patient with central diabetes insidious and explains that her kidneys are unable to absorb the proper amount of water due to defective hormone production. Which of the following areas of the nephron is normally impermeable to water regardless of serum vasopressin levels? PCT Late PCT Descending limb Ascending limb DCT Collecting duct

Ascending limb The ascending limb of the loop of Henle is impermeable to water regardless of serum vasopressin levels. Reabsorption of electrolytes by the Na+/K+/2Cl- cotransporter occurs in the thick ascending limb and contributes to formation of the aorticomedullar concentration gradient.

Renal physiologists at a national endocrinology research institute are studying how hydration status affects the mechanism of urine concentration and dilution in humans. To do this, they developed a technique in experimental animals that permits sampling of tubular fluid in different parts of the nephron. A tubular fluid sample with an osmolarity of 110 mOsm/L is obtained from a healthy animal after 12 hours of water deprivation. Assuming the physiology of this animal mirrors human physiology, which site was most likely sampled? PCT Desending limb Ascending limb DCT Collecting duct

Ascending limb. Dehydration stimulates ADH secretion. ADH ats on the collecting ducts, increasing their permeability to water. Thus, in the presence of ADH, the collecting ducts contain the most concentrated fluid in the nephron, while the thick ascending limb ascending limb of the loop of Henle and distal convoluted tubule contain the most dilute fluid.

_________________, is a humanized monoclonal antibody that interferes with VEGF receptor activation, thereby inhibiting angiogenesis.

Bevacuizumab A marked increase in vascular endothelial growth factor (VEGF) expression is thought to play a role in tumor angiogenesis.

A 45 yo man comes to the ED due to urinary incontience. he was diagnosed with multiple sclerosis a year ago after he developed transient acute vision loss in his right eye. A few weeks ago, he began having difficulty with his balance and had several episodes of urinary incontinece. The patient's walking has improved since, but he continues to urinate involuntarily. He has noticed increasing urinary frequency and cannot control the urge to urinate. His vital signs are normal. On examination, the patient has mild spastic paraparesis with increased reflexes in the lower extremities, bilateral Babinski sign; and a thoracic sensory level to pain, temperature, and vibration. An MRI of the spine reveals a new demyelinating lesion in the mid-thoracic spinal cord. Which of the following abnormalities will most likely be found on this patient's urodynamic studies. Bladder hypertonia Delayed bladder emptying Elevated urethral pressure Large residual volume of urine Reduced urine flow

Bladder hypertonia > This patient has urinary frequency and urge incontience in the setting of an overactive or *spastic bladder* due to the presence of an *upper motor neuron lesion* in the spinal cord. Patients with *multiple sclerosis* often develop a spastic bladder a few weeks after developing an acute lesion of the spinal cord. *Urodynamic studies* show little or no residual urine after emptying as bladder contractility is normal but distensibility is poor. The *bladder does not distend/relax* properly due to loss of descending inhibitory control from the upper motor neuron.

Nephrologists at a research hospital are investigating the physiologic changes that occur in DI. Their research specifically involves the renal mechanisms for excreting dilute urine in the setting of low serum antidiuretic hormone levels. The group develops a technique that permits sampling of tubular urine in experimental animals with physiology similar to that of humans. The animals then undergo hypophysectomy, after which tubular fluid samples are obtained from multiple sits through the nephron. In the absence of antidiuretic hormone, tubular fluid from which of the following sampling sites is most likely to have the highest osmolarity? PCT Descending loop Bottom of loop Ascending loop DCT Collecting duct

Bottom of loop > ADH acts primary on the collecting ducts, increasing their permeability to water. In the absence of ADH, the tubular fluid is most concentrated at the junction between the descending and ascending limbs of the loop of Henle and most dilute in the collecting ducts. > The descending limb of the loop of Henle is permeable to water, but not solutes. As this segment of the nephron descends into the medullary interstituium, water moves down its concentration gradient from the lumen into the highly osmotic medulla. No reabsorption of electrolytes occur in this segment, so the fluid in the lumen becomes hypertonic. In the absence of ADH, tubular fluid is most concentrated at the end of the descending limb of the loop of Henle.

A leading nephrology research institute is investigating the kidney's ability to clear various substances from the plasma. A healthy volunteer is given a slow IV infusion of PAH. The concentration of this substance is most likely to be lowest in which of the following nephron segments? Ascending limb Bowman's space Descending limb DCT PCT

Bowman space Para-aminohippuric acid (PAH) is primarily secretes into the nephron by the proximal tubule, but some is also freely filtered by the glomerulus. PAH is not reabsorbed by any portion of the nephron. Therefore, tubular fluid concentration of PAH is lowest in Bowman's space.

How would a pituitary tumor (eg. an ACTH-secreting adenoma causing Cushing's disease) affect renin and aldosterone?

Can result in secondary hypertension due to the mineralocorticoid activity of excess adrenal glucocorticoids. *The resulting HTN suppresses the renin-angiotensin-aldosterone axis, leading to low levels of renin and aldosterone.*

It is estimated that for PAH, the extraction ratio (arterial plasma PAH minus venous plasma PAH divided by arterial plasma PAH) is near 90% at arterial plasma concentrations lower than 20 mg/dL. Once the plasma concentration of PAH is increased above this level, the extraction ratio decreases progressively. Which of the following best explains the observed decrease in the PAH extraction ratio? Maximal excretion rate is reached Maximal reabsorption rate is reached Carrier transport is saturated Filtration fraction is decreased Renal plasma flow is decreased

Carrier transport is saturated > PAH is freely filtered from the blood in the glomerular capillaries to the tubular fluid in Bowman's space. It is also secreted from the blood into the tubular fluid by the cells of the proximal tubule by a carrier protein-mediated process. The secretion of PAH can be saturated at high blood concentrations.

A 62 yo woman with long-standing type 2 DM experiences progressive renal decline over 4-5 years despite optimal blood pressure control. She is started on interim hemodialysis and eventually undergoes transplantation of a deceased donor renal allograft. Three weeks following surgery, she experiences generalized malaise. Her past medical history is significant for diabetic retinopathy and osteoporosis, and her current medications include mycophenolate and tacrolimus. Labs show elevated potassium, BUN, creatinine. Cell-mediated immunity Drug toxicity Immune complex vasculitis Reno vascular disease Volume depletion

Cell-Mediated immunity > Acute renal allograft rejection can be an antibody-or cell-mediated process. Acute collar reaction is associated with diffuse lymphatic infiltration of the renal vasculature (endothelilits), tubules, and interstitium. > Mycophenolate and tacrolimus are immunosuppressant drugs commonly prescribed in early post transplantation patients to reduce the risk of acute rejection.

Serum _______________ is decreased in *Wilson disease* (hepatolenticular degeneration), which is clinically characterized by liver disease, motor abnormalities, and psychiatric symptoms.

Ceruloplasmin

A 64 yo man comes to the office for a new patient evaluation. He has recently moved to the area and reports chronic low back pain after an injury 8 years ago. The patient has since used several OTC angaesics. Most recently, he has been taking naproxen daily. He has no other joint pain, fever, skin rash, urinary symptoms, or the medical problems. On examination, the patient's BP is 135/70 and pulse is 78. He has trace lower extremity edema. The neurologic and musculoskeletal examinations show no abnormalities. Laboratory studies show blood count.

Chronic interstitial nephritis > NSAID-associated chronic renal injury is morphologically characterized by chronic interstitial nephritis and papillary necrosis. > NSAIDS concentrate in the renal medulla along the medullary osmotic gradient, with higher levels in the papillae. These drugs uncouple oxidative phosphorylation and are thought to cause glutathione depletion with subsequent lipid peroxidation, resulting in damage to tubular and vascular endothelial cells. Prolonged use results in *chronic interstitial nephritis*, seen as patty interstitial inflammation with subsequent fibrosis, tubularly atrophy, papillary necrosis and scarring, and caliceal architecture distortion. > NSAIDs also decrease prostaglandin synthesis, causing constriction of medullary vasa recta and *ischemic papillary necrosis*

A 23 yo man comes to the office due to 3 weeks of malaise and fatigue. He says, "Ive been sick with the flu for the last 3 weeks. I don't know why I'm not getting better". The patient also has profound fatigue causing difficulty with day-to-day activities. His temperature is 101.2 F. Cardiac auscultations reveals an apical holosystolic murmur radiating to the axilla, which was not heard during previous office visits. Lab evaluation show serum creatinine of 2.3. Mild proteinuria and microscopic hematuria with red cell casts are present on urinalysis. Which of the following is the most likely pathogenesis of this patient's renal finding? Anti-glomerular basement membrane antibodies Circulating immune complex-mediated injury Endotoxin-induced renal tubular injury Hematogenous metastatic infection focus Thrmobembolic event

Circulating immune complex-mediated injury > The most likely cause of fever and fatigue with new-onset cardiac murmur is infective endocarditis (IE). Diffuse, proliferative glomerulonephritis secondary to circulating immune complex deposition may complicate IE and can result in acute renal insufficiency. Hypercellularity similar to that seen in post streptococcal glomerulonephritis or membraneoproliferative glomerulonephritis is revealed on high microscopy.

A 7 yo boy is brought to the ED by his parents for abdominal pain and arthralgia. He has a cough and runny nose last week by otherwise has been in good health. The patient's temperature is 98.6, pulse is 92, and respirations are 20. Physical examination shows palpable purpura over his buttocks and thighs. Auscultation of the lungs and heart is normal. His abdomen is diffusely tender to palpation without rebound or guarding. Both knees are tender but do not appears warm or swollen. A stool occult blood test is positive. Urinalysis results show: Protein 2+, Blood: moderate, Leukocyte esterase: trace; Nitrites: Negative, WBC: 1-2; RBC: many: Casts: RBC casts Which of the following mechanisms is the most likely underlying cause of this patient's condition? Antibody-dependent cellular cytotoxicity Circulating immune complexes Delayed hypersensitivity reaction Disseminated bacterial infection IgE-dependent degranulation

Circulating immune complexes > Henoch-Schonlein purpura is an *IgA-mediated type III hypersensitivity reaction in children that generally follows infectio*n. Deposition of circulating IgA-containing immune complexes in small vessels resulting in systemic vasculitis. Common manifestations include palpable lower-extremity purpura, abdominal pain, arthralgia, and hematuria.

A 34 yo male who is being treated for acute leukemia develops olguria. his serum creatinine level si 2.7. Renal biopsy rivals multiple uric acid crystals obstructing renal tubular lumen. The principle site of uric acid precipitation would be which of the following? Proximal tubule due to high solute concentration Proximal tubules due to impaired uric acid transport Loop of Henle due to urine hyposmarlity Distal tubules due to high urine flow rate Collecting ducts due to the low urine pH.

Collecting ducts due to low urine pH > Tumor lysis syndrome occurs when tumors with a high cell turnover are treated with chemotherapy. The lysis of tumor cells causes intracellular ions, such as potassium and phosphorus, and uric acid (metabolite of tumor nucleic acid) to be released into serum. Uric acid is soluble at physiologic pH, but it can precipitate in the normally acidic environment of distal tubules and collecting ducts. The prevention of tumor lysis syndrome includes urine alkalinizaiton and hydration, as high urine flow and high pH along the nephron preventing crystallization and precipitation of uric acid.

A 34 yo man is brought to the hospital by ambulance after being involved in a motor vehicle collision. He was an unrestrained passenger and sustained considerable trauma. On arrival to the ED, he is hypotensive and bleeding from several sites. The patient receives an emergency blood transfusion as part of the resuscitation efforts. Abdominal ultrasound reveals splenic laceration and blood in the peritoneal cavity. En route to the operating room, the patient develops difficulty breathing, chills, and pain in the chest and back. Urine drainage from the Foley catheter was initially clear but not appears brown in color. Which of the following is the most likely cause of this patient's new findings? CD8+ lymphocyte-mediated cytotoxicity Complemented-mediated cell lysis Endotoxin-induced TNF-alpha surge IgE-meidated reaction to serum proteins Vascular deposition of immune complexes

Complemented-mediated cell lysis > Acute hemolytic transfusion reaction is a antibody-mediated (type II) hypersensitivity reaction caused by preexisting anti-ABO antibodies that bind antigens on transfused donor erythrocytes. Subsequent complement activation results in erythrocyte lysis, vasodilation, and symptoms of shock. Common findings include fever, hypertension, chest and back pain, and hemoglobinuria.

A researcher is studying the effector various manipulations on kidney blood flow and glomerular filtration. Which of the following is most likely to both decrease renal plasma flow and increase the filtration fraction? Hyperproteinemia Bladder neck obstruction Construction of the efferent arteriole Construction of the afferent arteriole Dilation of the efferent arteriole.

Construction of the efferent arteriole

A 48 yo woman is elevated for postcoital bleeding and vaginal discharge. Pelvic examination shows a friable mass of the cervix that bleeds easily on touch. Cerival biopsy confirms invasive squamous cell cancer confirmed to the cervix and uterus. Lymph node metastases are not seen. A radical hysterectomy is performed during which the right ureter is accidentally injured but then repaired. Imaging studies performed after the surgery show a partial obstruction of the right ureter with milk dilation of the proximal collecting system. Which of the following changes are most likely to be seen in the right kidney? Changes in the GFR and FF.

Decrease GFR Decrease FF > Acute ureteral construction or obstruction decreases the glomerular filtration rate and filtration fraction.. With acute ureteral obstruction (first 12 hours), the RPF may transiently increase; however, with time, efferent arteriolar constriction (in response to reduced GFR) will decrease RPF. Even at later stages, though, the GFR remains depressed to a greater extent than the RPF, resulting in *reduced FF*.

A 55 yo woman comes to the physician with increased swelling around her ankles and face that has progressively worsened over the last 1-2 months. Her cardiopulmonary examination is normal. She has 2+ bilateral pitting edema in the lower extremities, trace edema in the upper extremities, and periorbital edema. Laboratory evaluation shows a serum creatinine level of 2.0 mg/dl and an albumin level of 2.8 g/dL. Urinalysis shows 3+ proteinuria and no hematuria or casts. Kidney biopsy is performed; light microscopic finding following staining with hematoxylin and eosin are show in the image below showing nodules. Which of following is the most likely explanation for this patient's biopsy findings? Bee sting with severe allergic reaction Diabetes mellitus Hepatitis C infection HIV C infection Lung carcinoma Recent streptococcal pharyngitis Systemic lupus erthematosus Treatment with procainamide

Diabetes mellitus > Diabetic nephropathy often results in progressive proteinuria with the eventual development of nephrotic symptoms and renal failure. Hyaline arteriosclerosis and nodular glomerulosclerosis (Kimmelstiel-Wilson nodules) are seen on renal biopsy. *The presence of Kimmelstiel-Wilson nodules indicates irreversible glomerular damage and predicts a rapid decline in kidney function. *

A 67 yo old man man comes to the generalized weakness, easy fatiguability, anorexia, and intermittent nausea for the past several months. He also says that he is "itching and scratching a lot" Physical examination shows bilateral lower extremity pitting edema and skin excoirations.. Laboratory resulting show a serum creatinine level of 3.4 and BUN level of 48. A renal biopsy is performed. Light microscopy of the tissue sample shows widespread narrowing of the renal articles with deposition of homogenous, glassy material in the sub endothelial space that stains pink with periodic acid-Schiff (PAS) stain. This patient most likely has which of the following underlying conditions? Atheroembolic renal disease Diabetes mellitus Malignant Hypertension Multiple myeloma Rapidly progressive glomerulonephritis

Diabetes mellitus > This patient's symptoms (eg. fatigue, weakness, itching) are most likely due to accumulation of uremia toxins secondary to progressive *chronic kidney disease*. His renal biopsy shows deposition of eosinophilic hyaline material in the intimal and media of small arteries and arterioles, which is characteristic of *hyaline arteriolosclerosis*. It is typically seen in patients with untreated or poorly controlled *hypertension* (HTN) or *diabetes mellitus* > Homogenous deposition of eosinophilic hyaline material in the intimal and media of small arteries and arterioles characterizes hyaline arteriolosclerosis. This is typically produced by untreated or poorly controlled hypertension and/or diabetes.

A 23 yo man comes to the ED due to abdominal pain and nausea for the last few hours. He also reports an epodes of vomiting and has noticed that his urine has a fruity odor. The patient has had increased thirst and urination for the past several days along with weight loss. He has non known medical problems and take no medications. PE reveals pallor with cool extremities. The abdomen is a soft, without tenderness to palpation. Laboratory studies are ordered to confirm the diagnosis. What does the patient most likely have to explain this patient's acid-base status?

Diabetic keotacidosis (DkA) DKA is characterized by polydipsia, polyuria, and a fruity order to the breath and/or urine (ketones). DKA is associated with elevated anion gap metabolic acidosis the tis usually accompanied by compensatory respiratory alkalosis. The combination yields a low pH, low serum bicarbonate, and low PaCO2.

Researchers working at a national foundation for prematurity and birth defects are investigating the pathological changes that can occur during embryonic kidney development. Their research focuses on the molecular mechanisms underlying formation of the definitive kidney. Specifically, the inductive signals exchanged between the metanephric diverticulum and metanephric mesoderm that drive their differentiation into tissues forming the mature kidney. If a toxic insult occurs during early fetal development that selectively inhibits the renal structures formed by the metanephric mesoderm, which of the following adult derivatives will fail to develop? Collecting ducts DCT Major calyces Minor calyces Renal pelvis

Distal convoluted tubules > The ureteric bud ultimately gives rise to the *collecting system of the kidney, including the collecting tubules and cuts, major and minor calyces, renal pelvis, and the ureters*. The metanephric mesoderm (blastema) gives rise to the glomeruli, Bowman's space, proximal tubules, the loop of Henle, and Convoluted tubules).

A 32 yo man comes to the ED with severe right flank pain. Urinalysis shows microscopic hematuria. His temperature is 98 F, BP is 125/85 and pulse is 92. He has no CVA tenderness. Abdominal imaging shows a 5 mm distal right ureteric calculus. The patient is started on IV hydration and analgesics. His symptoms resolve and he passes the stone within a few hours. The patient says he "feels" fine" and refuses further workup. Which of the following recommendations would most likely prevent a recurrence of this patient's condition? Drinking plenty of water daily Following a high=protein diet Following a high-sodium diet Following a low-calcium edit Taking a short course of antibiotics Taking pyridoxine daily

Drinking plenty of water daily Urine supersaturation is the main mechanism underlying all types of renal stones. Low-fluid intake increases the concentration of stone-forming agents, thereby promoting stone formation. All patients with nephrolithiasis should be advised to consume ample water and clear liquids. NOTE: Dietary calcium helps bind oxalate in the gut to form unabsorbalbe calcium oxalate. Low-Calcium diets allow increased amounts of free oxalate to be absorbed and then excreted in the kidney, thereby causing hyperoxaluria.

A 24 yo female presents to your office with burning during urination, urine clouding and urinary frequency. She denies fever, chills and flank pain. She had a similar episode before that was treated with antibiotics. She has no other medical problems and does not use tobacco, alcohol, or drugs. Her vitals signs are stable. Physical examination shows suprapubic tenderness. Which of the following bacteria is most likely to be isolated from this patient's urine? Klebsiella pneumoniae, Salmonella typhi Salmonella enteritidis Campylobacter jejune Shigella dysenteriae Proteus mirabilis Yersinia enterocolitica Haemophilus influenzae Vibrio cholerae Streptococcus pyogenes Streptococcus pneumoniae Entamoeba histolytica E. coli

E coli > E. coli is the most common pathogen causing cystitis and acute pyelonephritis. The second most common cause of UTI in sexually active women is Staphylococcus saprphyticus. UTIs most commonly affect women because of their very short urethra;

A 44 yo man comes to the office for a routine check-up. PMH is significant for hypercholesterolemia, which he has controlled through diet. His father died of a MI at age 56, and his mother, who is still living, has a history of stroke. On physical examination, the patient's BP is 160/100 and heart rate is 70. He is started on enalapril.. During the first 7 days of therapy, the patient's GFR is decreased. Which globular structure is affected by a downstream effect of enalapril and is therefore responsible for this patient's renal response.

Efferent arterioles Enalapril is a ACE inhibitor. All ACE inhibitors decrease circulating levels of angiotensin II, a substance that cause - systemic vasoconstriction - Preferential constriction of the glomerular efferent arteriole - Enhancement of adrenal aldosterone secretion.

A 7 yo previously healthy body is brought to the office due to swelling of the hands and feet. Two weeks ago, the patient was treated for anaphylaxis following a bee sting. During the past 10 yeas, he has had progressive hand and foot swelling, and his pants feel "tighter" than usual. The patient's urine has also become "frothy". Examination show periorbital edema, pitting edema of the hands and feet, as well as mild ascites. Lungs are clear to auscultation. Labs shows: Elevated: Total cholesterol, LDL, Triglycerides Protein in urine, hyaline casts What is most likely abnormal in this patient? BP Electron microscopy of a glomerular filtration unit Immunofluorescent microscopy of a glomerular filtration unit Left ventricular ejection fraction Light microscopy of a glomerular filtration unit Serum tryptase level

Electron microscopy of a glomerular filtration unit > Nephrotic syndrome is characterized by generalized edema, hyperlipidemia, hypoablumiemia, and massive proteinuria (resulting in "frothy" urine". > Minimal change disease is the most common cause of nephrotic syndrome in children. Classic manifestations include proteinuria, hypoabluminemia, and edema that are usually reversible with corticosteroids. The principle lesions is a diffuse foot process effacement that can be seen on electron microscopy. Light and immunofluorescence microscopy typically are normal.

A 63 yo man comes to the physician after noticing a reddish tinge to his urine for the last couple of days. during evaluation of his hematuria an abdominal CT scan reveals a left-sided renal mass. Further workup also shows multiple pulmonary and bone nodules. CT-gudied biopsy of a peripherally located lung noodle demonstrates renal cell carcinoma. High-dose interleukin-2 (IL-2) is tarted, and 4 weeks later there is significant reduction in his tumor burden. Which of the following mechanisms was most likely responsible for regression of his malignancy? Anti-angiogenic effect of IL-2 Direct cytotoxic effect of IL-2 on the tumor cells Enhanced activity of NK cells IL-2 induced apoptosis of tumor cells Increased expression of MHC Class I on tumor cells

Enhanced activity of NK cells > Interleukin-2 (IL-2) is produced by helper T cells and stimulates the growth of CD4+ and CD8+ T cells and B cells. IL-2 also activates NK cells and monocytes. The increased activity of T cells and NK cells is thought to be responsible for IL-2's anticancer effect on metastatic melanoma and renal cell carcinoma.

A high serum _____________ count is seen with *drug-induced interstitial nephritis*. The most common offenders include beta-lactam antibiotics, NSAIDs, diuretics, and anticonvulsants.

Eosinophil

____________________________, can develop secondary to HIV infection, heroin abuse, and severe obesity. Sclerotic change in some portions of some glomeruli are noted on light microscopy

Focal segmental glomerulosclerosis

__________________ results from inadequate enlargement of the peritoneal cavity in utter. The viscera protrude through an abdominal wall defect adjacent to the umbilicus. Viscera are not covered by perineum.

Gastroschisis

A 68 yo man comes to the ED due to abdominal pain and nausea pain and nausea for the past 2 days. He has a history of atherosclerotic cardiovascular disease and underwent canary artery bypass surgery 2 years ago. BP is 105/65 mmHg and heart rate is 120/min and irregular. Abomdinal examination reveals mild diffuse tenderness and decreased bowel sounds Lab suites are as follows pH 7.25 PaCo2: 29 Lactic acid, venous blood: Elevated ECG shows absent P waves and irregular rate and rhythm. CT scan of the abdomen reveals clonic wall thickening an no enhancement with IV contrast. Urinalysis shows acidic urine. Renal metabolism of which of the following amino acids is most important for maximizing acid excretion in this patient? Alanine Arginine Aspartate Glutamine Histidine

Gluatmine > Acidosis stimulates renal ammoniagenesis, a process by which renal tubular epithelial cells metabolize glutamine to glutamate, generating ammonium that is excreted in the urine and bicarbonate that is absorbed into the blood. The process is responsible for the vast majority of renal acid excretion in chronic acidotic states. NOTE: > Arginine is a urea cycle intermediate that helps to remove nitrogenous waste products (eg. ammonium) from the blood. Hepatic metabolism of ariginien results in the production of urea and ornithine. > Histidine, an essential amino acid, is converted to histamine by histidine decarboxylase. Histamine is involved in the acute inflammatory response and gastric acid secretion; it also functions as a neurotransmitter.

A 65 yo man comes to the office for evaluation of blood in the urine. The patient has no abdominal pain, urinary frequency, or urgency. he has HTN, Type 2 DM, and stage II chronic kidney disease. He quit smoking 10 years ago and had smoked a pack of cigarettes daily for 30 years. On examination, vital signs are within normal limits. The patient's BMI is 33 kg/m2. Appropriate work-up is performed, and he undergoes a renal biopsy. The histopatholgic findings are displayed on the slides below showing rounded/polygonal cells with abundant clear cytoplasm. Which of the following processes most likely account for the abnormal appearance of these cells? Glycogen and lipid accumulation Karyorrhexis Membrane lipid peroxidation Mitochondrial swelling Pigment accumulation

Glycogen and lipid accumulation Gross painless hematuria in an older adult should be considered a sign of urinary tract cancer (urotheliail or renal cell carcinoma) until proven otherwise. This patint's renal biopsy shows rounded/polygonal cells with abundant clear cytoplasm, which is characteristic of clear cell carcinoma, the most common form of renal cell carcinoma. Clear cell carcinoma originates from proximal tubular epithelial cells and contains copious amounts of intracellular glycogen and lipids. Standard tissue fixation and staining technique typically solve glycogen and lipids from pathogenic specimens, leaving *Clear spaces*

A 44 yo man with polycystic kidney disease undergoes a renal transplant. A week later, he develops low-grade fever, body aches, and decreased urine output. His temperature is 99 F, BP is 124/76, and pulse is 88. Abdominal examination show mild tenderness over the graft on palpation. His current serum creatinine is 2.2 but was only 1.2 two days ago. Arterial and venous Droppler studies reveal adequate graft perfusion. Graft biopsy demonstrates dense interstitial infiltration by mononuclear cells. Which of the following is the most likely cause of this patient's current condition? Graft B-cell sensitization against host MHC antigen Graft T-cell sensitization against host MHC antigens Host B-cell sensitization against graft MHC antigens Host T-cell sensitization against graft MHC antigens Preformed antibodies against graft ABO antigens

Host T-cell sensitization against graft MHC antigens. Organ rejection can be hyper acute, acute, and chronic. Acute cellular rejection most often occurs within weeks of translation due to sensitization of host *T lymphocytes against donor MHC (HLA) antigens*. This causes a mononuclear (i.e.. lymphocytic) infiltrate on histopathology and graft dysfunction. Prevention is attempted with calcineurin inhibitors, and treatment includes systemic corticosteroids.

Autoantibodies are responsible for type ____________ hypersensitivity reactions including autoimmune hemolytic anemia (drug-induced or warm/cold agglutinin disease), immune thrombocytopenia purpura, pemphigus vulgarism, and Goodpatsure syndrome.

II > Type II hypersensitivity reaction can also occur due to production of antibodies against foreign antigens (eg. erythroblastosis fettles, ABO mismatched transfusion)

A 9 yo girl is brought to the office due to a 2 day history of face and eye puffiness. The mother reports that the child was treated for a rash on the leg with an antibiotic 3 weeks ago. The girl's temperature is 99 F and blood pressure is 150/90. She has generalized edema but no skin rash. urinalysis reveals proteinuria and hematuria. Renal biopsy is performed and results of electors microscopy show depositions. What is the area most likely made of? Albumin leak Eosinophil enzymes Fibrin deposition Hyaline accusation Immune complex deposits Lipid droplet Neutrophil enzymes

Immune complex deposits > The patient has Poststreptococcal glomerulonephritis represent immune complexes composed of IgG, IgM, and C3 NOTE > Hyaline, acellular deposits composed of plasma proteins, can be seen in Kimmelstiel-WIlson nodules of diabetic nephropathy > Prominent fibrin deposition is characteristic of rapidly progressive glomerulonephritis (RPGN) > Lipid droplets in renal tubules may be seen in conditions causing nephrotic syndrome; however, this is uncommon with PSGN. > Neutrophils and monocytes infiltrates the glomerular mesangium in PSGN, contirubitng to the hyper cellular appearance on light microscopy. Enzymatic granules are small intracellular structures that do not appear homogenous on electron microscopy.

A 9 yo boy is brought to the physician by his parents after developing red-color urine earlier that day. On physical examination, the patient has periorbital edema and mild pedal edema. His other medical problems include asthma and atopc dermatitis. He was recently treated for impetigo. Which of the following immune components is most likely responsible for the damage caused to this patient's kidneys? Autoantibodies CD8+ T lymphocytes Histamine Immune complexes Macrophages

Immune complexes > Patents with post-streptococcal glomerulonephritis present with edema, hematuria, and an antecedent history of streptococcal infection (eg. impetigo, cellulitis, pharyngitis). Infection must be caused by a nephritogenic strain of group A beta-hemolytic Streptococcus. The glomerulonephritis is mediated by a type III (immune complex) hypersensitivity reaction.

Describe the Ca2+ and, 1,25-dihydroxyvitamin D, PTH, PO4 levels in Chronic Kidney disease.

In *chronic kidney disease* (CKD), PO4 clearance declines due to the fall in GFR. > The *increased PO4* binds free serum Ca2+, resulting in *hypcalcemia*. > Loss of normal renal parenchyma reduces 1,25-dihydroxyvitamin D synthesis, resulting in a significant decline in intestinal Ca2+ absorption and Ca2+ release from bone. > This further exacerbates the hypocalcemia, which along with hyperphosphatemia and low calcitriol, stimulates PTH production (*secondary hyperparathyroidism*)

An experimental substance is infused IV at a constant rate into healthy volunteer. The substance is known to selectively constrict the efferent arteriole in renal glomeruli. The rate of infusion is closely controlled during the experiment to allow for only mild constriction of the efferent arteriole. Which of the following changes in the GFR and FF is most likely to occur during the infusion of this substance?

Increase GFR Increase FF

A yo boy is brought to the office by his mother due to facial puffiness that is especially noticeable in the morning. He has a history of mild, intermittent asthma that is well controlled with albuterol as needed. Temp is 97, BP is 98.62 and pulse is 89 and regular. Physical examination shows bilateral lower extremity pitting edema. Nephrotic range proteinuria consisting mainly of albumin is revealed on urinalysis. Which of the following mechanisms is the most likely cause of this patient's abnormal laboratory findings? Impaired tubular reabsorption of filtered proteins Increased filtration of plasma proteins Inflammation of the urinary tract Necrosis of skeletal muscle fibers Overproduction of low-molecular-weight proteins.

Increased filtration of plasma protein > Minimal change disease. Loss of foot process and charge barrier.

A 5 yo is brought to the office by his mother, who notes that her son's eyes and feet have looked puffy over the last several weeks. She is unaware of exactly when this began but says the patient had a mild upper respiratory tact infection several weeks ago. The boy had no pain but mentions that his shoes seems to fit tightly and bother him, especially when he runs outside during recess at school. The mother also remarks that the boy's urine has been excessively foamy recently. On further questioning, the mother states that she has seasonal allergies and ask whether her child also has allergies. Physical examination is remarkable for periorbital edema and lower extremity edema. Urinalysis shows 4+ proteinuria but is otherwise unremarkable. Which of the following secondary changes is most likely in this patient? Decreased liver albumin synthesis Decreased plasma aldosterone levels Increased capillary oncotic pressure Increased liver lipoprotein synthesis. Increased renal sodium wasting

Increased liver lipoprotein synthesis > Minimal change disease is the most common childhood nephrotic syndrome. It typically presents suddenly after an upper respiratory infection. Increased glomerular capillary permeability causes massive protein (eg. albumin) loss in the urine. Hypoalbuminemia reduces plasma oncotic pressure, which causes a fluid shift into the interstitial space, resulting in edema. *Low oncotic pressure also triggers increased lipoprotein production in the liver (i.e., hyperlipidemia)* PRESENT with *hypoalbuminemia, generalized edema, and hyperlipidemia. > Low intravascular oncotic pressure stimulates *increased lipoprotein production* in the liver. impaired lipid catabolism due to decreased lipoprotein lipase and abnormal transport of circulating lipid particles also contributes to hyperlipidemia.

A 42 yo man with a long history of type 1 diabetes mellitus comes to the office due to frequency involuntary loss of urine. For the past several months, he has been having difficulty starting and maintaining a urinary stream. In the last 3 weeks, he has had 2 episodes of nocturnal enuresis and multiple daytime episodes of uncontrolled voiding without any sensation of a full bladder. His the medical problem include Chronic kidney disease and gastroparesis. he does not use tobacco or alcohol. Which of the following additional findings would most likely be present in this patient? Enlarged prostate on recta examination Increased postvoid residual volume Loss of sensation in perineal area Lower extremity hyperreflexia Mini-mental state examination score of 22

Increased postvoiid residual volume Diabetic autonomic neuropathy is common in type 1 diabetic and can cause overflow inconteinece due to inability to sense a full bladder and incomplete emptying. > Postvoid residual (PVR) testing with ultrasound or catheterization can confirm inadequate bladder emptying.

A 38 yo man is brought to the ED due to progressive nausea, confusion, and unsteady gait. Family members state that symptoms started 4 days after he went to the density due to a toothache, for which he was prescribed ibuprofen. He also take lithium for bipolar disorder. On examination, he is drowsy and ataxic, having slurred speech and coarse tremors. His serum lithium level is 3.86 (above therapeutic range) and serum creatinine and BUN are elevated. While in the ED, he develops a generalized tonic-clonic seizure. During emergent hemodialysis treatment, his blood is passed along a semipermeable membrane and allowed to equilibrate with a dialystate solution. Which of the following is most likely to increase the rate of drug removal? Adding lithium to the dialysis solution Decreasing dialysis solution temperature Decreasing the membrane pore size Increasing surface area of the membrane Increasing thickness of the membrane

Increasing surface area of the membrane > Diffusion speed across a semipermeable membrane increases with higher molecular concentration gradients, larger membrane surface areas, and increased solubility of the diffusing substance. Diffusion speed decreases with increased membrane thickness, smaller pore size, higher molecular weights, and lower temperature.

_____________________ increases expression of MHC class I & II, improving antigen presentation in all cells.

Interferon-gamma

The research division of a large pharmaceutical company focuses their efforts on studying renal tubular transport proteins. A substance is identified that specifically and completely inhibits glucose transport in the proximal renal tubules. In a healthy volunteer receiving this substance, glucose clearance will best approximate the clearance of which of the following? Inulin PAH Alanine Urea Sodium

Inulin > Glucose is normally filtered at the glomerulus and completely reabsorbed by the proximal tubule. Inhibition of sodium-coupled, carried, mediate transport of glucose by the proximal tubule would cause the glucose clearance to approach the value of the GFR, which is typically. estimated by calculating the clearance of inulin. .

_____________________ classically presents with muddy brown, granular, and epithelial cell casts and free tubular epithelial cells in the urine

Ischemic tubular necrosis

A 28 yo man comes to the physician with muscle weakness and headaches for the last 2 months. He denies palpitations, tremors, or increased sweating. His blood pressure is 190/120 and his pulse is 68. His serum potassium level is 2.8 mEq/L. The patient's plasma renin activity is high and his serum aldosterone levels are elevated. A 24 hour urine collection shows increased potassium excretion. Which of the following is the most likely cause of this patient's symptoms? Adrenal cortical tumor Adrenal medullary tumor Juxtaglomerular cell tumor Pituitary tumor Primary hypertension

Juxtaglomerular cell tumor > Elevated serum aldosterone levels can manifest with HTN, hypokalemia, and muscle weakness. Increased levels of both renin and aldosterone are indicative of secondary hyperaldosteronism, which can be caused by renovascular disease, malignant HTN, and renin-secreting tumors.

A 63 yo man is being evaluated by hospital house staff after being admitted from the ED for fever, anorexia, and discomfort associated with breathing. He has a history of frequent and extended travel to Sub-Saharan Africa. The patient has never had regular medical care in the U.S due to his extensive traveling, and thus his medical history is known. Radiologic studies of the chest show multiple round lesions in both lung fields. Laboratory evaluation reveals a hematocrit of 56%. Biopsy of one of the lesions reveals the findings seen on the side below showing rounded and polygonal cells with abundant clear cytoplasm. Which of the following is the most likely primary location of this patient's metastatic disease? Liver Stomach Colon Kidney Brain

Kidney Clear cell carcinoma is the most common subtype of renal cell carcinoma and is composed of large, rounded or polygonal cells with clear cytoplasm. The classic triad of hematuria, flank pain, and palpable mass occurs in a minority of patients. Non-specific symptoms and paraneoplastic syndromes are more common. These tumors are often incidentally at an advanced stage, and the lung is the the most common site for metastasis.

An apparently healthy 6 yo boy is enrolled in a research study designed to assess the amino acid absorptive capacity of the intestine. As part of the investigation, he is administered an oral solution containing free amino acids. Blood samples ar ethen obtained at 15 min intervals for the next 2 hours. The boy is found to have signifcnalty decreased intestinal absorption of lysine, arginine, omithine, and cysteine as compared to the other study participants. If his condition is left untreated, which of the following complications is this patient at greatest risk of developing? Aortic dissection Emphysema Fat malabsorption Intellectual disability Kidney stones Rickets

Kidney stone > The dibasic amino acid cysteine, ornithine, lysine, and arginine (cola) share a common transporter in the intestinal lumen and kidneys. In patients with *cystinuria*, this transporter is defective, resulting in impaired renal and intestinal absorption of these amino acids. NOTE > Aortic dissection is a well known complication of *Marfan syndrome* and other connective tissue disorders > Emphysema is a common complication of alpha-1-antitripsin deficiency. Liver insolvent is also common in this disorder > Fat malabsorption is typically seen in conditions that cause exocrine pancreas dysfunction, such as *cystic fibrosis* > Intellectual disability occurs in several inborn error of amino acid metabolism including *phenylketonuria, homocystinuria, and in some patients with maple syrup urine dieases (branched-chain ketoaciduria)* However, intellectual disability is not seen in cystinuria.

____________________ are relatively common in healthy pubertal men as the aorta and superior mesenteric artery can pores the left renal vein ("nutcracker effect"), resulting in increased intravascular pressure in the left gonadal vein with retrograde blood flow and ______________ formation.

Left-sided varicoceles ; varicocele A new-onset left varicocele associated with ipsilateral flank pain and hematuria should raise suspicion for RVT causing impaired left gonadal venous drainage.

A 5 yo boy is brought to the physician with generalized edema that developed following a mild upper respiratory infection. His past medical history is unremarkable. The patient's blood pressure and heart rate are normal. Serum creatinine levels are normal. urinalysis shows massive proteinuria with no hematuria. Further analysis reveals that the patient urine protein consists principally of albumin with only traces amount of IgG and alpha2-macroglubulin. Which of the following pathogloic changes is the most likely cause of this patient's urinary protein loss? Thinning of the glomerular basement membrane Glomerular present formation Loss of glomerular basement membrane anions Nodular glomeruloscerlosis Tubular necrosis and epithelial shedding

Loss of glomerular basement membrane anions > Minimal change disease

A renal calculus is classified as "stag horn" when it fills the renal pelvis and assumes its shape. Stag horn calculi consists of ____________________ and are associated with infection by urease-forming organism such as *Proteus*.

Magnesium triple phosphate (struvite)

___________________ results from failure of obliteration of the vitelline (or omphalomesentetic duct). Toddlers may have painless gastrointestinal bleeding due to ectopic gastric mucosa.

Meckel diverticulum

A 34 yo misionar in southern Asia is traveling to a remote village and becomes stranded when his bus breaks down. He has no access to water for 36 hours, during which his urine osmolarity reaches 1100 mOsm/L. Urine concentration depends primarily on the serum level of vasopressin, which is regulated by the neurohypophysis in response to plasma osmolarity and blood volume. Which of the following nephron segments responses to vasopressin by increasing absorption of a specific solute that is important for generating a high medullary concentration gradient? Cortical segment of the collecting duct Early distal tubule Medullary segment of the collecting duct Proximal tubule Thin ascending limb of the loop of Henle.

Medullary segment of the collecting duct > ADH acts on the medullary segment of the collecting duct to increase urea and water reabsorption, allowing for the production of maximally concentrated urine.

A 17 yo boy is brought to the office due to occasional blood in the urine. The first episode occurred 1 year ago, about 3 days after a flulike illness, and resolved spontaneously. He had a similar episode after 6 months ago, which also seemed to resolve. He does not have any other medical problems and does not use tobacco or alcohol. There is no history of blood or kidney disorders in the family. The physical examination shows a healthy appearing young male. His vital signs are normal. On lab evaluation, BUN level is 14, and creatinine is 0.8 mg/dL. Urinalysis results are as follows: SP: 1.013 Protein: +2 Blood: Trace Glucose: Negative Ketone: Negative Leukocyte esterase: Negative Nitrites: Negative WBC: 1-2 RBC: 20-30 A renal biopsy is performed. Which of the following is most likely to be seen on microscopic evaluation? Apple-green birefringement mesangial deposits Present formation with linear IgG deposits Effacement of podocyte foot processes Granular IgG and C3 deposits Lamellate basement membrane Mesangial deposition of IgA Sclerosis of a portion of some glomeruli Thin basement membrane

Mesangial deposition of IgA > IgA nephropathy (Berger disease) frequently presents as recurrent, self-limited, painless hematuria with 5 days after an upper respiratory infection (synpharyngitic hematuria). Kidney biopsy will show mesangial IgA deposits on immunofluorescence. In contrast, post-streptococcal glomerulonephritis is seen 1-3 weeks after streptococcal pharyngitis and is usually not recurrent.

What would the lab result of pyleonephritis look like?

Microscopic urinalysis findings are similar to a UTI (bacteria, leukocytes, nitrates, leukocyte esterase) with the addition of WBC casts.

A 4-yo girl developed acute-onset colicky abdominal pain, vomiting, and loose bloody stool during a family vacation. She was treated with supportive care and began to feel better. A few days later, her parents bring her to the ED because she has urinated only once in the past 10 hours and the urine was red. Physical examination shows conjunctival pallor but is otherwise normal. Laboratory studies are as follows: Low platelet, low hemoglobin, high creatinine. Urinalysis shows proteinuria and hematuria. Which of the following mechanisms is the most likely cause of this patient's condition? Microthrombi in small blood vessels Streptococcal antigen-associated glomerular damage Systemic IgA-mediated vasculitis Vasculitis involving medium arteries Widespread activation of the coagulation cascade

Microthrombi in small blood vessels > This patient has diarrhea-associated *hemolytic uremic syndrome (HUS)*, a major cause of acute renal failure in young children. Most cases are due to intestinal infection by *Shiga toxin (vertoxin)-producing organism* (eg. E coli 0157:H7, Shigella dysenteiae). > These toxins injure the endothelium of preglomerular arterioles and glomerular capillaries, leading to platelet activation and aggregation and formation of microthrombi. > Platelet consumption causes *thrombocytopenia (platelets <140,000), but there is typically no purpura or active bleeding. > Erythrocytes passing through the damaged capillaries suffer shear injury and broken down to schistocytes, causing *microangiopathic hemolytic anemia* (conjunctival pallor). >Extensive damage to the renal vasculature results in *acute kidney injury* (oliguria/anuria, hematuria, increased creatinine). Hemolytic uremic syndrome is a common cause of acute renal failure in children. It is characterized by the train of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Most cases develop following a diarrheal illness caused by Shiga toxin-producing organism (eg. E coli O157:H7, Shigella dysenteriae)

Scientists studying the kidney's response to hypoprerufsion ally a clip to a pig's right renal artery, which significantly reduces blood flow to the kidney. After 6 months, they perform a right neurectomy and examine the glomeruli microscopically. Which of the following cell types would be mot likely to undergo hyperplasia as a result of the clip placement? Cuboidal epithelial cell of the proximal tubules Endothelial cells of the efferent arteriole Intraglomerular mesangial cells Modified smooth muscle cells of the afferent arteriole Squamous epithelial cells of the thick ascending limb of the loop of Henle

Modified smooth muscle cells of the afferent arteriole > Renal artery stenosis causing significant renal hypo perfusion will result in decreased GFR and subsequent activation of the renin-angiotensin system. This leads to increased renin released by modified smooth muscle (JG) cells within the afferent glomerular arterioles. Chronic renal hypo perfusion can cause hyperplasia of the JG apparatus.

Describe the amount of potassium in the tubular fluid as it flows along the nephron in comparison to the filtered potassium load.

Most of the K+ filtered by the glomeruli is resorbed in the proximal tubule and loop of Henle. The last distal and cortical collecting tubules are the primary sites for regulation of K+ concentration in the urine. K+ depletion stipulates alpha-intercalated cells to reabsorb extra potassium; principle cells secrete K+ under conditions of normal or increased K+ load.

A 64 yo man comes to the office due to persistent back pain, constipation, and easy fatiguability for the last several months. BP is 115/75 and pulse is 88. The patient has dry mucus membranes. Lab results are as follows: - Elevated BUN and creatinine, and protein. Renal biopsy is performed and light microscopy shows atrophic tubules, many of which contain large, obstructing, intensely eosinophilic casts. Which of the following is the most likely diagnosis?

Multiple myeloma Multiple myeloma (MM) should be suspected when an elderly patient has one or more the following: 1) Fatiguability (due to anemia) 2) Constipation (due to hypercalcemia) 3) Bone pain, most commonly in the back and ribs (bone lysis due to production of osteoclast-activating factors by myeloma cells) 4) Elevated serum protein (monoclonal proteins) 5) Renal failure Myeloma cast nephropathy ("myeloma kidney") due to excess excretion of free light chains (*Bence Jones proteins*) is the most common form of nephropathy in MM. These proteins are filtered by the glomerulus in small amounts and then reabsorbed in the tubules. Progress to tubular obstruction and epithelial injury leading to impaired renal function.

A 32 yo man comes to the ED due to sudden sones of severe right flank pain that radiates towards the groin. He also has gross hematuria but no fever or dysuria. The patient has no significant medical problems and has never experienced similar symptoms. He does not take any medications. Temperature is 98.1 F, BP is 120.80, and pulse is 88. The right flank is tender to palpation. There is no CVA tenderness. Imagine shows a stone in the middle of the right ureter. Which of the following is the most likely to be seen on lab evaluation of this patient? (With calcium levels in the blood an urine)

Normocalcemia, hypercalciuria > *Calcium stones* represent 75-80% of all renal calculi and include calcium oxalate and calcium phosphate stones. *Hypercalcuria* is the most common risk factor for development of calcium stones in adults. In most patients, the hypercalciuria is *idiopathic* and thought to be due to increased GI absorption, increased mobilization of calcium from bone, or decreased renal tubular calcium reabsorption. > However, these patients remain *normocalcemic* due to intact regulation of serum calcium levels by vitamin D and parathyroid hormone.

A 45 yo man with end stage polycystic renal disease undergoes decreased-donor kidney transplantation. His postoperative course is unremarkable with normal functioning of the renal allograft. Four years later, the patient develops HTN. Laboratory studies show a progressive increase in serum creatinine levels over the last few months. Urinalysis is within normal limits. On ultrasonography, the transplanted kidney is reduced in size. A biopsy of the graft is most likely to show which of the following? Dense mononuclear interstitial infiltration Glomerular crescent formation Obliterative vascular fibrosis Tubular hypertrophy and intratubular casts Vascular fibrinoid necrosis and neutrophil infiltration

Obliterative vascular fibrosis Chronic renal allograft rejection manifests months to years after transplantation and presents with worsening HTN and a slowly progressive rise in serum creatinine. it is mediated by a chronic, indirect immune response against donor allogantigens and results in obliterative intimal thickening, tubular atrophy, and interstitial fibrosis.

A hospital wants to estimate the prevalence of diabetic neprhotpathy in the sounding population of adults with Type 2 diabetes. Kidney biopsy samples are obtained from 500 patients with diabetes. The samples are then interpreted by 15 different pathologists, 5 of whom work at the hospital and 10 of whom work at other institutions. A preliminarily analysis shows that the pathologists who work for the hospital are 3 times more likely to interpret the biopsy samples as diabetic nephropathy compared to those who do not work for the hospital. Which most likely explains this difference in interpretation? Confounding Lead-time bias Observer bias Recall bias Selection bias

Observere bias > Observer bias occurs when the investigator's evaluation is *affected by preconceived expectations or prior knowledge, typically leading to overestimation of the disease association or treatment effects*. This type of bias can be reduced by conducting a blinded study in which observers are unaware of study details and patient characteristics that could unduly influence them. NOTE: > Selection bias can occur with inappropriate (i.e., nonrandom) selection methods or through selective attrition of the study participants. For example, a large number of patients drop from a clinical trial due to the severity of side effects associated with the treatment. This type of attrition is selective (i.e.. different attrition rate between groups) and will reduce the generalizability of the group.

A 64 yo woman comes to her nephrologist for a regular follow-up appointment. The patient's medical problems include diabetes mellitus for 20 years and stage IV chronic kidney disease with a glomerular filtration rate <30. She takes daily insulin and has made lifestyle modifications. recently, her blood glucose has been well controlled. The patient's other medical problems include HTN and dyslipidemia, which are controlled with medication. Her BMI is 27. Cardiopulmonary examination is normal. Lower extremity examinations show trace bilateral edema and 2+ pulses. This patient is at greatest risk for which of the following long-term complications of her renal disease? Hypercalcemia Hyperthyroidism Hyzpoparathryoidm Osteodystrophy Retinal neovascularizaiton

Osteodystrophy > Patients with chronic kidney disease may develop renal osteodystorphy from secondary hyperparathyroidism (caused by hyperphosphatemia and hypocalcemia)

A 65 yo man comes to the office due to SOB and cough for 2 months. He also has had a 5 kg unintentional weight loss during that time. The patient has smoked 1-2 packs of cigarettes, daily for the last 50 years. Chest x-ray shows a 3.8 cm right lung mass with enlarged mediastinal lymph nodes. Lab show elevated calcium. A bone scan is negative for focal lytic lesion. Which of the following is most likely to be elevated in this patient? 1,25 hydroxyvitamin D PTH PTHrP Serum phosphorus Serum thyroxine

PTHrP This patient has a prolonged history of smoking, respiratory symptoms, weight loss, and lung mass on chest x-ray that is probably a primary lung cancer His evaluation is notable for hypercalcemia but no focal bone lessons, which is consistent with *humoral hypercalcemia of malignancy (HM).* HHM is caused by secretion of *parathryoid hormone-related protein*, which closely resembles PTH at the bioactive amino-terminal region and acts similar to PTH. PTHrP causes increased bone

Describe the following levels in multiple myeloma Parathyroid hormone Urinary calcium 1,25-dihydroxyvitamin D Parathyroid hormone-related protein

Parathyroid hormone - Decrease Urinary Calcium - Increase 1,25-dihydroxyvitamin D - Decrease Parathyroid hormone-related protein - Normal > *Hypercalcemia* in MM is the result of osteolysis induced by tumor cells, which relase osteoclast-activating factors. When the PTH-caclium (Ca2+) axis is intact, elevation in serum Ca2+ *inhibits PTH production*. PTH is responsible for Ca2+ reabsorption in the distal tubules and collecting ducts of the kidney. Low levels of PTH cause increased urinary loss of Ca2+ (hypercalciura). Because the urinary loss of Ca2+ is less than the Ca2+ gained from bone resorption, serum Ca2+ remains elevated. > Hypercalcemia and light chain cast nephropathy in MM frequently cause progressive renal failure. This leads to loss of the 1-alpha-hydroxylase enzyme and suppression of 1-alpha-hydrxoyalse activity (due to hyperphosphatemia and low PTH) resulting in *low-1,25,dihydroxyvitamin D* levels.

A 68 yo male presents to your office complaining of urgency, frequency, a weak urinary steam, and straining on micturition. These symptoms have been present for the past few years, but have gradually become more severe. He also notes nocturne, as well as oliguria alternating with polyuria. The patient's kidneys are most likely to demonstrate: Glomerular sclerosis and hylainosis Tubular epithelial dyspasia Hyperplastic arteriolar change Ischemic tubular necrosis Parenchyma pressure atrophy

Parenchymal pressure atrophy *Benign prostatic hyperplasia leads to intermittent bladder outlet obstruction and overflow incontience.* Urinary retention results in increased pressure in the urinary tract and resultant reflex nephropathy. Ultimately, hydronephrosis and renal interstitial atrophy and scarring ensue. The condition should be promptly treated as prolonged obstruction can cause permanent damage and chronic renal failure. NOTE: > Glomerular sclerosis and hyalinosis is often seen in diabetic nephroscerosis > Epithelial dysplasia marks an altenration in cell architecture. Cells change in shape, size, and staining. Nuclei enlarge as well. Dysphasia is considered a precursor of malignancy. Being prostatic hyperplasia does not predispose to renal tubular dysplasia. > Hyperplastic arteriolar changes are induced by long-standing systemic HTN. > Ischemic tubular necrosis results from hemorrhage, low-flow states (such as MI), or systemic vasodilation (such as sepsis). Its symptoms are those of acute renal failure: Oliguria, increased serum Bun and creatinine (azotemia), fluid overload, and electrolyte disturbances.

A 3 week old boy with discharge from the umbilicus is brought to the clinic by his parents. His postnatal course was uncomplicated, with shriveling of the cord around 14 day of life. Vitals signs are normal. Examination of the area reveals a small reducible umbilical hernia, minimal clear to straw-colored discharge from the umbilicus, and erythema around the area. Laboratory results are as following: Neutrophils: Increased Lymphocytes: Increased Absence of neutrophil migration Duplication of the ureter Incomplete closure of anterior abdominal wall Persistence of allantois remnant Persistence of omphalmesenteric duct

Persistence of allantois remnant > The urachus is a remnant of the allantois that connects the bladder with the yolk sac during fetal development. Failure of the urachus to obliterate at birth results in a patent urachus, which can facilitate discharge of urine from the umbilicus.

A 50 yo man with polycystic kidney disses comes to the office due to constant, deep pain in his shoulders, arms, and legs. Other medical problems include hypertension treated with rampiril. The patient's BP is 150/85 and pulse is 78. Cardiopulmonary examination is normal. Abdominal examination shows large, palpable renal masses. Traces bilateral lower-extremity edema is present. His lab results from 2 years ago show BUN of 25 and creatinine of 2.3. Current laboratory results are: High: BUN High: Creatinine Low: Calcium Describe the metabolic state for: - Phosphate - PTH - Calcitriol

Phosphate: Increase PTH: Increase Calcitriol: Decrease > Chronic kidney disease cause a decrease in GFR, which decreases the filtered phosphate load causing elevated serum phosphate levels. > Hyperphosphatemia reduces serum free calcium concentrations and stimulates osteocytes and osteoclasts to release fibroblast growth factor-23 (FBF-23), a circulating peptide that functions to decrease proximal tubule phosphate reabsorption. > Elevated levels of phosphate and FGF-23 also *Reduce calcitriol synthesis*, resulting in decreased intestinal calcium and phosphate absorption. > Hypocalcemia and hyperphsophatemia also *increase parathyroid hormone (PTH) secretion*, which stipulates osteoclasts to increase bone turnover.

A 21 yo male presents to his physician after noticing the this urine had a "frothy" appearance. He also complains of easy fatiguability and anorexia. His PMH is significant only for an upper respiratory infection several weeks ago. Physical examination rivals symmetric pitting edema of the ankles. Which of the following is most likely decreased in this patient? Capillary hydrostatic pressure Interstitial fluid pressure Plasma oncotic pressure Tissue lymphatic drainage Circulating aldosterone level

Plasma oncotic pressure > Frothy, foamy urine may be caused by proteinuria or bile salts in the urine. This patient's history of recent upper respiratory infection and ankle edema on physical exam suggest a diagnosis of nephrotic syndrome with associated low serum albumin. Hypoalbuminemia lowers the plasma oncotic pressure and causes interstitial edema formation due to net plasma filtration. Minimal change disease (MCD) is the most common cause of nephrosis in children, and can occur in adults as well.

______________________ presents most commonly in children with hematuria, HTN, and periorbial edema,. TBC casts and mild proteinuria may be present on urinalysis, and serum creatinine may be elevated

Post streptococcal glomerulonephritis

A 34 yo woman with a history of UTI comes to the physican with dysuria and increased urinary frequency. Her urine culture grows colonies of Gram-negative bacteria. The bacteria are isolated and placed in a growth-enchanting nutrient solution, where they undergo rapid cellular division. As they are actively dividing, the bacterial cell are lysed and their DNA is extracted and purified. Analysis of the partially replicated DNA fragments shows in presence of uracil. This finding is most likely mediated by which of the following enzymes? DNA ligase DNA polymerase I DNA polymerase III Gyrate Helices Primase

Primase Primate is a DNA-depedent RNA polyermase that incorporates short RNA primers into replicating DNA.

An 86 yo man is hospitalized for a complicated hip fracture requiring surgical repair following a fall. His medical problems include prostate cancer, gout, and osteoarthritis. An indwelling urinary catheter is placed due to intimal urinary retention and immobilization following the surgery. On the eight day of hospitalization, the patient develops fever and altered mental status. After evaluation and laboratory testing, a urinary tract infection is diagnosed. Which of the following is the most effective strategy for preventing this complication? Antibiotic-Coated urinary catheter Bladder irrigation Prompt removal of catheter when no longer indicated Prophylactic antibiotics Routine replacement of catheter

Prompt removal of catheter when o longer indicated UTIs are common in hospitalized patients with indwelling urinary catheters. The risk for UTI can be reduced by avoiding unnecessary catheterization, using sterile technique when inserting the catheter, and removing the catheter as soon as possible.

A 43 yo male is diagnosed with hepatic cirrhosis due to prolonged heavy alcohol consumption. He develops massive ascites and lower extremity edema that responds well to furosemide therapy. However, a week later the patient receives high-dose ibuprofen for joint pains and soon develops worsening abdominal distention. Blunting of the diuretic response in this patient is due to interruption of which of the following substance? Prostaglandins Endothelia Angiotensin II Aldosterone Natriuretic peptides Bradykinin

Prostaglandins > Furosemide is a loop diuretic that works by inhibiting Na-K-2Cl symporters in the ascending limb of the loop of Henle. It binds to symporters and effectively block Na and Cl transport resulting in increased Na, Cl, and fluid excretion. *Additionally loop diuretics also stimulate prostaglandin release, loop diuretics also increase renal blood flow leading to increased GFR and enacted drug delivery. Both factors ultimately enhance diuretic response.* NSAID drugs like ibuprofen inhibit prostaglandin synthesis. Thus concurrent use of NSAIDs with loop diuretics can result in a decreased diuretic response.

A 54 yo man hospitalized with an acute myocardial infarction goes into cardiac arrest. The patient is resuscitated successfully and transferred to the cardiac intensive care unit where he remains hemodynamically stable. However, on the second day of hospitalization, his urine flow diminished to 400 mL/day. On physical examination, the patient's blood pressure is 115/68 and pulse is 78 min. Laboratory results are as follows: Increase: BUN and Creatinine Decrease: Sodium, Potassium, Chloride, Bicarbonate Urine sediment microscopy reveals muddy brown casts. Which of the following renal structures are most likely to demonstrates signs of ischemic injury in this patient? Collecting ducts Distal tubules Glomeruli Proximal tubules Renal papillae

Proximal tubules > Acute tubular necrosis can be caused by decreased renal perfusion due to severe hypovolemia, shock, or surgery. The straight proximal tubules and the thick ascending limb of Henle's loop located in the outer medulla are the most commonly affected portions of the nephron. Muddy brown casts are pathognomonic for acute tubular necrosis. > This patient most likely has *acute tubular necrosis (ATN) due to decreased renal perfusion during his cardiac arrest (cariogenic shock). Ischemic ATN is one of the most common causes of acute kidney injury in hospitalized patient. ATN presents with *increased serum creatinine* and blood urea nitrogen (BUN) levels, a normal BUN/serum creatinine ratio, and *oliguria* (low urine output). > Ischemic injury predominantly affects the *renal medulla*, which has low blood supply even under normal conditions. The straight portion of the *proximal tubule* and the *thick ascending limb* of Henle's loop are particularly susceptible to hypoxia, as they participate in the active (ATP-consuming) transport of ion and have hight oxygen demand.

A 39 yo old paraplegic man with an indwelling bladder catheter comes to the ED complaining of 24 hours of rigors, nausea, and vomiting. His temperature is 102 F. Physical examination shows suprapubic and costovertebral angle tenderness. Urinalysis shows 3+ leukocyte esterase and numerous WBCs. Urine and blood cultures grow non-lactose-fermenting Gram-negative rods. Which of the following pathogens is the most likely culprit?

Pseudomonas aeruginosa. > Patients with indwelling bladder catheters are at increased risk for UTIs caused by both typical (eg, E coli, Klebsiella pneumoniae, Staphyl saprophyticus, Proteus mirabilis) and opportunistic (eg. Pseudomonas, Enterococcus, other staphylococci, fungal, organisms. This patient's culture results are consistent with Pseudomonas aeruginosa, the only non-lactose-fermenting, Gram-negative rod listed. It is also the only one that is *oxidase positive*.

Acute _____________ presents with fever, flank pain, pyuria, and possible white cell casts

Pyelonephritis

A 1 hour boy is in the neonatal intensive care unit with tachypnea and hypoxia. The infant was born at 39 weeks gestation via cesarean delivery due to variable decelerations. The pregnancy was complicated by a lack of prenatal care. The infant weights 3.2 kg. Physical examination shows a flattened nose and bilateral club feet. Breath sounds are marked diminished bilaterally. The infant is intubated an mechanically ventilated, but his oxygen levels do not improve. The infant dies 1 hour later. Which of the following is most likely to be found during autospy? Congenital diaphragmatic hernia Duodenal atresia Renal genesis Surfactant deficiency Tracheoseophgeal Fistula

Renal Agenesis > Potter sequence results from a renal anomaly that causes decreased fetal urine output leading to oligohydramnios. The lack of amniotic fluid causes compression of the fetus (characteristic facies and limb abnormalities) and pulmonary hypoplasia, which is the most common cause of death in affected infants)

An 18 yo man comes to the office due to a progressive skin rash over the past year. He also has a long-standing history of an intermittent burning sensation in his palms and soles that is exacerbated by stress and fatigue. The burning sensation is particularly severe after exercise, during which the patient notes that he sweats minimally. Skin examination shows clusters of non-glancing, red papule in the gluteal, inguinal, and umbilical areas. Laboratory evaluation reveals an undetectable level of alpha-galactosidase A. Which of the following conditions is this patient at greatest risk for developing? Ataxia Hepatomegaly Neurofibrosarcoma Optic atrophy Renal failure

Renal failure > In Fabry disease, alpha-galactosidase A deficiency causes accumulation of the sphingolipid globotriaosylceramide. > The earliest manifestation of Fabry disease are neuropathic pain and angiokeratomas. > Glomerular (eg. proteiniuria, renal failure), cardiac (eg. left ventricular hypertrophy), and cerebrovascular (eg. transient ischemic attack, stroke) complications develop in adulthood.

A 24 yo woman comes to the office for a routine antenatal ultrasound. She is 19 weeks pregnant by her last menstrual period. This is the patient's third pregnancy, and there have been no complications. her family history is unremarkable, and both of her children are healthy. The ultrasound reveals a male fetus with bilaterally enlarged fetal kidneys with diffuse small cysts. The amniotic fluid volume is very low. no the anomalies are seen. Which of the following will most likely be present in the newborn after delivery? Bladder distension Cerebral aneurysm Hypertension Respiratory distress Vebebral anomalies

Respiratory distress > In its most severe phenotype, autosomal recessive polycystic kidney disease can be detected on prenatal sonogram along with oligohydraminos. Potter sequence (flattened facies, limb deformities, pulmonary hyoplasia) is caused by oligohydraminos and is associated with high mortality.

A 44 yo homeless man with a history of alcohol abuse is brought to the hostpial after being found unresponsive. His temperature is 96; BP is 90/60 and pulse is 110. He is responsive only to pain and has dry mucus membranes. The patient is initially treated with IV fluids, and his mental status slowly improves but then he develops decreased urine output and flank pain. A renal biopsy is eventually perform,d which reveals marked ballooning and vacuolar degeneration of proximal renal tubules; multiple oxalate crystals are observed in the tubular lumen. Which of the following is the most likely pathogenesis of this patient's renal failure? Advanced liver disease Chronic undernutrition Prolonged hypotension Severe infection Toxic renal injury

Toxic renal injury Ethylene glycol ingestion leads to toxic, acute tubular necrosis with vacuolar degeneration and ballooning of the proximal tubular cells. Typical clinical findings include high anion gap metabolic acidosis, increased osmolar gap, and calcium Theylene glycol is rapidly absorbed from the GI tract and metabolized to glycol acid (toxic to renal tubules) and oxalic acid, which precipitates as calcium oxalate crystals.

A 68 yo man comes to the physican complaining of gradual reddening of his urine over the last 3 months. His other medical problems include osteoarthritis, for which he takes OTC ibuprofen. He lives at home with his wife and spends most of his free time working in his backyard greenhouse. Prior to his retirement, he worked at a rubber manufacturing plant for 35 years. His serum creatinine is 1.1. Which of the following is most likely to be discovered on further work-up? Hemorrhagic cystitis Rapidly progressive glomerulonephritis Renal cell carcinoma Staghorn calculus in the kidney Transitional cell carcinoma of the bladder

Transitional cell carcinoma of the bladder > Transitional cell carcinoma of the bladder typically presents as gross hematuria in an elderly man. A history of smoking or occupational exposure to rubber, plastics, aromatic amine-containing dyes, textiles, or leather increases the risk of developing transitional cell carcinoma.

A 36 yo woman comes to the office due to frequent uriantion since an exacerbation of multiple sclerosis 2 months ago. Most of symptoms including dizziness, leg weakness, and numbness, have improved with corticosteroid treatment. However, she has continued difficulty holding urine, and on several occasions has passed a small amount of urine while trying to reach the bathroom. She has no urine leakage during coughing or sneezing. Th patient has no other medical problems. Her abdomen is soft and contender. Neurological examination shows hyperreflexia and increased tone in the lower extremities. Her postpaid residual volume is low. What could most likely explain her urinary symptoms?

Uninhibited bladder contraction > Multiple sclerosis (MS) is likely an autoimmune disease that causes varying degrees of demyelination, inflammation and gloss in the central nervous system. > Regions in the pons and cerebral cortex partially inhibit the micturition reflex and also regulate contraction/relaxation of the external urethral sphincter. > Spinal cord lesson above the sacral region cause a loss of higher center control of micturition and lead to detrusor hyperreflexia and urge incontinence. Patients typically develop a frequency urge to urinate and pass a small amount of urine. As the disease progress, the bladder can become atonic and dilated leading to overflow incontinence.

A 45 yo woman comes to the office due to polyuria and nocturne. She has no fever, dysuria, or abdominal pain. The patient has no significant medical problems and takes no medications. Her temp is 98 F, BP is 120/80, and pulse is 76. The patent's mucous membrane appear dry. The remainder of her physical examination is normal. Her urine output and osmolarity remains unchanged with water deprivation for several hours, but after administration of desmopressin, urine output decreases and urine osmolarity increases. Renal clearance of which of the following substances would decrease the most after this patient's injection? Calcium Creatinine Glucose Para-amino hippuric acid Urea

Urea Vasopressin and desmopressin cause a V2 receptor-mediated increase in water and urea permeability at the inner medullary collecting duct. The resulting rise in urea reabsorption (decreased urea clearance) enhances the medullary osmotic gradient, allowing the production of maximally concentrated urine. Note: > Creatinine is freely filtered by the glomerulus, and a small amount is also secreted by the proximal tubule. No further secretion or reabsorption occurs beyond the proximal tubule.

A 34 yo primigravida at 18 weeks gestation comes to the office for a routine prenatal examination. The patient's pregnancy has been uncomplicated. She takes a daily prenatal vitamin, and her prenatal laboratory results have been normal to date. The patient's personal and family medical histories are unremarkable. During the visit, a detailed fetal ultrasound reveals unilateral hydronephrosis. Male external genitalila are visible If the fetal hydronephrosis is caused by obstruction, which of the following is the most likely site? Spinal cord Uteropelvic junction Urethra Urinary meatus Vesicoureteral junction

Ureteropelvic junction > Inadequate canalization of the ureteropelvic junction, the connection site between the kidney and the ureter, is the most common cause of unilateral fetal hydronephrosis.

A 35 yo man who works as a nurse in local hospital is brought to the ED with confusion and leathery. His temperature is 98 F, blood is 86/48, pulse is 120, and respirations are 12. Arterial blood gas results shows pH 7.59, pCO2 49 and pO2 85. Which of the following lab studies would be the most useful for diagnosing the cause of this patent's acid-base abnormality? Serum ketones Serum osmolality Serum sodium Urine chloride Urine glucose

Urine Chloride Metabolic alkalosis is characterized by high pCO2 (>40 mm Hg) because the accumulated HCO3- causes a compensatory decrease in ventilation. This patient has *metabolic alkalosis*. Ascertaining the patient's *volume status* and checking the *urine chloride* are important steps in the workup of metabolic alkalosis. The most common causes of metabolic alkalosis are: - *Vomiting or nasogastric suctioning*: Loss of H+ and Cl- ion (hydrochloric acid) in gastric secretions causes a net gain of alkali in the body, leading to metabolic alkalosis. Present with low urine (Cl-) (Saline-responsive) - *Thiazide or loop diuretics use*: Block absorption of Na+ and Cl- ion at the DCT and loop of Henle, respectively. These mechanisms increase Na+ reabsorption in the collecting tubule at the expense of increased K+ and H+ urinary losses, leading to metabolic alkalosis. Patient present with high urine Cl- (>20 mEq/L) when diuretic use is ongoing, and low urine Cl- (<10 mEq/L) after it stopped. (Saline-responsive) - Mineralocorticoid excess state: Persistent mineralocorticoid activity increase Na+ reabsorption and urinary K+ and H+ losses, leading to a relative increase in serum HCO3-. These patients present with HTN and high urine Cl- (>20 mEq/L) due to the expanded extracellular fluid volume causing pressure natriuresis. (saline-unresponsive).

A 60 yo man comes to the office due to dark, rusty-colored urine for the last 2 weeks. He reports no pain, urinary frequency, or urgency. The patient has no chronic medical problems and takes no medication. He smoked a half pack of cigarettes daily for 10 years and quite smoking for 30 years ago. His father has HTN and his mother has Alzheimer dementia. Urinalysis shows a large umber of RBCs. A renal ultrasound is performed and reveals a mass in the right kidney. Cytologic evaluation of the mass shows malignant cells with chromosome 3p deletion. The deletion most likely vin voles which of the following genes? c-MYC NF-1 RB VHL WT-1

VHL The patient with hematuria, a renal mass, and malignant cell on histopathology most likely has *renal cell carcinoma*. The majority of renal cell neoplasms re sporadic. Patients with both sporadic and hereditary (associated with von Hippel-Lindau disease) renal cell carcinomas are found to have deletions or mutations involving the VHL gene on chromosome 3p.

A 23 yo woman is being evaluated for recurrent episodes of UTI. She has had 5 episodes of cystitis and an episode of pyelonephritis over the past year. The symptoms tend to occur a few days following sexual intercourse. The patient has no other medical problems and take no medications. her temperature is 98 F, Bp is 110/70, respirations are 16, and pulse is 65. Abdominal and genitourinary examination are normal. Which of the following is the most likely predisposing factor for pyelonephritis in this patient. Frequent voiding Hematogenous bacterial spread Suppression of endogenous flora Urethral colonization Vesicoureterual urine reflux

Vesicoureteral urine reflux > Suppression of endogenous flora, colonization of the distal urethra by pathogenic gram-negative rods (eg. E. Coli, Klebsiella, Proteus) and Enterococcus, and attachment of these pathogens to the bladder mucosa are the stages of pathogenesis in lower UTI. Anatomic or functional vesicoureteral reflux is almost always necessary for the development of acute pyelonephritis.

A 13 yo Caucasian female presents to your office with urine discoloration. She had been treated for facial impetigo three weeks ago. Urinalysis shows hematuria, mild proteinuria, and occasional RBC casts. Renal biopsy is most likely to demonstrate: Basement membrane splitting on light microscopy Diffuse capillary wall thickening on light microscopy Linear IgG and C3 deposits on immunofluorescent microscopy Glomerular basement membrane disruptions and fibrin deposition on electron microscopy Discrete subepithelial humps on electron microscopy

When an *older child or young adult* presents with edema, hematuria and proteinuria a few weeks following a skin or pharyngeal infection, post-streptococcal glomerulonrphtitis (PSGN) is the most likely diagnosis*. In this condition, an inflammatory reaction involves all glomeruli in both kidneys. The kidneys are enlarged and swollen, with multiple surface punctate hemorrhages. Immunofluorescence reveals coarse granular deposits of IgG and C3 that have a characteristic "lumpy-bumpy" appearance.

The concentration of PAH, creatinine, inulin and urea ____________ as fluid runs along the proximal tubules, while the concentrations of bicarbonate, glucose, and amino acids __________________

increase ; decrease > Urea is ultimately secrreted in very high concentrations, as it is a waste product of metabolism > Bicarbonate is actively reabsorbed in the proximal tubule due to the activity of carbonic anhydrase with proximal tubular cells. This reabsorbing force causes the concentration of bicarbonate to decrease as fluid runs along the proximal tubule.

Hepatitis C infection is associated with _________________. On light microscopy, the glomeruli appear hyper cellular with thickening and splitting of the glomerular basement membrane due to sub endothelial immune complex deposition.

membranoproliferative glomerulonephritis

A 23 yo man with a history of Type 1 DM is brought to the ED due to the confusion and weakness. His symptoms began 2 days ago after he started having mild diarrhea. He has missed several doses of insulin because his appetite has been poor. On examination, his breath has a mildly fruity odor. This patient is most likely to demonstrate which of the following urine chemistry patterns? (pH, HCO3-, H2PO4)

pH: Low HCO3-: Low H2PO4-: High This patient has diabetic ketoacidosis which is characterized by decrease serum pH and HCO3- with a compensatory decrease in pCO2.