Physio Renal USMLE

373. A 69-year-old man presents with symptoms of thirst and dizziness, and physical evidence of orthostatic hypotension and tachycardia, decreased skin turgor, dry mucous membranes, reduced axillary sweating, and reduced jugular venous pressure. He was recently placed on an angiotensin-converting enzyme (ACE) inhibitor for his hypertension. Urinalysis reveals a reduction in the fractional excretion of sodium and the presence of acellular hyaline casts. The internist suspects acute renal failure of prerenal origin associated with increased renin secretion by the kidney. A stimulus for increasing renal renin secretion is an increase in which of the following? a. Angiotensin II b. Atrial natriuretic peptide (ANP) c. GFR d. Mean blood pressure e. Sympathetic nerve activity

373. The answer is e.

374. A patient with uncontrolled hypertension is placed on a new diuretic targeted to act on the Na+ reabsorption site from the basolateral surface of the renal epithelial cells. Which of the following transport processes is the new drug affecting? a. Facilitated diffusion b. Na+/H+ exchange c. Na+-glucose cotransport d. Na+-K+pump e. Solvent drag

374. The answer is d.

375. A 28-year-old woman presents to her physician's office with fatigue, malaise, and orthostatic dizziness. When asked what medications she is taking, she stated that she has been taking 800 mg ibuprofen four to six times a day for painful menstrual cramps. Serum creatinine was elevated to 2.1 mg/dL. Which of the following is most likely to produce an increase in GFR in patients with acute renal failure? a. Administration of angiotensin II b. Contraction of glomerular mesangial cells c. Dilation of afferent arterioles d. Increased renin release from the juxtaglomerular apparatus e. Volume depletion

375. The answer is c.

377. An 83-year-old woman with a history of hypertension presents to her family physician's office with oliguria. Serum creatinine and BUN are elevated and a computed tomography (CT) reveals that the patient's left kidney is hypoplastic. Renal function studies are performed to assess the renal handling of various substances. Substance X is injected into an arterial line. All of substance X appears in the urine and none is detected in the renal vein. What do these findings indicate about the renal handling of substance X? a. It must be filtered by the kidney. b. It must be reabsorbed by the kidney. c. Its clearance is equal to the GFR. d. Its clearance is equal to the renal plasma flow (RPF). e. Its urinary concentration must be higher than its plasma concentration.

377. The answer is d.

379. An 85-year-old woman presents with a fever and hypovolemic hypotension. To assess her renal function, the filtration fraction is determined using a freely filterable substance that is neither reabsorbed nor secreted. The infusate yields a renal artery concentration of 12 mg/mL and a renal vein concentration of 9 mg/mL. Which of the following is her filtration fraction? a. 0.05 b. 0.15 c. 0.25 d. 0.35 e. 0.45

378. The answer is d.

381. A 54-year-old man with small cell lung cancer presents with lethargy, confusion, and muscle cramps. Blood work shows an increase in plasma levels of antidiuretic hormone (ADH). In patients with the syndrome of inappropriate antidiuretic hormone (SIADH), which of the following will increase? a. Intracellular volume b. Plasma oncotic pressure c. Plasma osmolarity d. Plasma sodium concentration e. Urine flow

381. The answer is a.

383. A 46-year-old man presents to his physician with a 12-week history of frontal headaches. CT of the brain shows a mass in the posterior pituitary, and the posterior pituitary "bright spot" is absent on MRI. The patient also complains of increased thirst and waking up frequently during the night. Which of the following best describes his urine? a. A higher-than-normal flow of hypertonic urine b. A higher-than-normal flow of hypotonic urine c. A lower-than-normal flow of hypertonic urine d. A lower-than-normal flow of hypotonic urine e. A normal flow of hypertonic urine

383. The answer is b.

386. A 24-year-old man with a history of renal insufficiency is admitted to the hospital after taking a large amount of ibuprofen. His BUN is 150 mg/dL. This patient's high serum urea nitrogen was most likely caused by which of the following? a. Decreased GFR b. Decreased secretion of urea by the distal tubules c. Increased reabsorption of urea by the proximal tubules d. Increased renal blood flow (RBF) e. Increased synthesis of urea by the liver

386. The answer is a.

387. A 52-year-old man presents to his internist for a 6-month checkup following diuretic therapy and recommended diet changes for his essential hypertension. His blood pressure is 145/95 mm Hg and serum aldosterone levels are increased. Aldosterone secretion is increased when there is a decrease in the plasma concentration of which of the following? a. Adrenocorticotropic hormone (ACTH) b. Angiotensin II c. Potassium d. Renin e. Sodium

387. The answer is e.

388. A 76-year-old man presents at the emergency department with headache, vomiting, shortness of breath, insomnia, and confusion. He is found to be oliguric with an increased BUN and creatinine. Urine-specific gravity is low and there is proteinuria. Which of the following statements concerning the normal renal handling of proteins is correct? a. Proteins are more likely to be filtered if they are negatively charged than if they are uncharged. b. Proteins can be filtered and secreted but not reabsorbed by the kidney. c. Most of the protein excreted each day is derived from tubular secretion. d. Protein excretion is directly related to plasma protein concentration. e. Protein excretion is increased by sympathetic stimulation of the kidney.

388. The answer is e.

389. A 92-year-old man presents with dehydration following 4 days of persistent diarrhea. Under this circumstance, hypotonic fluid would be expected in which of the following? a. Glomerular filtrate b. Proximal tubule c. Ascending limb of the loop of Henle d. Cortical collecting tubule e. Distal collecting duct

389. The answer is c.

391. An 18-year-old man presents with muscle weakness, cramps, and tetany. Blood pressure is normal and no edema is present. Laboratory analysis reveals hypokalemic alkalosis, hyperaldosteronism, and high plasma renin activity, diagnostic of Bartter's syndrome. Which of the following statements best describes the action or secretion of renin? a. It converts angiotensin I to angiotensin II. b. It converts angiotensinogen to angiotensin I. c. It is secreted by cells of the proximal tubule. d. Its secretion is stimulated by increased mean renal arterial pressure. e. Its secretion leads to loss of sodium and water from plasma.

391. The answer is b.

392. A patient with multiple myeloma develops type II RTA with a defect in proximal tubular bicarbonate reabsorption. Which of the following structural features distinguishes the epithelial cells of the proximal tubule from those of the distal convoluted tubule? a. The distal tubule has a thicker basement membrane. b. The distal tubule has fewer tight intercellular junctions. c. The distal tubule has more microvilli. d. The proximal tubule forms the juxtaglomerular apparatus. e. The proximal tubule has a more extensive brush border.

392. The answer is e.

393. A 63-year-old hospitalized woman becomes oliguric and confused. A blood sample is drawn to measure her glucose concentration, which is found to be 35 mg/dL. An IV access is obtained and an ampule of 50% dextrose is given followed by a continuous infusion of 10% dextrose. Most of the glucose that is filtered through the glomerulus undergoes reabsorption in which of the following areas of the nephron? a. Proximal tubule b. Descending limb of the loop of Henle c. Ascending limb of the loop of Henle d. Distal tubule e. Collecting duct

393. The answer is a.

394. A 56-year-old man with hypertension presents with complaints of flushing and orthostatic hypertension. Blood analysis reveals an increased plasma renin activity and hyperlipidemia. Urinalysis reveals a decreased GFR and an increase in urinary albumin excretion. Gadolinium-enhanced three-dimensional magnetic resonance angiography is suggestive of renal artery stenosis. Measurement of RBF and a renal arteriogram are ordered to evaluate the patient for atherosclerotic renal vascular disease (ARVD = renal artery stenosis and ischemic nephropathy). The effective RPF, determined from the clearance of PAH, is less than the true RPF because of which of the following? a. The calculated clearance of PAH depends on the urinary flow rate. b. The cortical and medullary collecting ducts are able to reabsorb some PAH. c. The fraction of PAH filtered is less than the filtration fraction. d. The measured value of the plasma PAH concentration is less than the actual PAH concentration. e. The plasma entering the renal vein contains a small amount of PAH.

394. The answer is e.

395. A 64-year-old elementary school teacher complains of a strong sense of urinary urgency followed by incontinence of large amounts of urine as she tries to rush to the bathroom. She also states that she has had urinary frequency as well as nocturia over the last week. Her past medical history is insignificant, but she was recently diagnosed with a urinary tract infection last week. The patient is diagnosed with an overactive bladder with urinary incontinence. She is treated with behavioral training and oxybutynin. What neurotransmitter is responsible for initiating bladder (detrusor) contraction? a. Acetylcholine b. Epinephrine c. GABA d. Norepinephrine e. Serotonin

395. The answer is a.

396. A 14-year-old girl with polycystic kidney disease has a decrease in both GFR and RBF. The nephrologist wants to administer a drug that will increase both GFR and RBF. Both GFR and RBF would increase if which of the following occurred? a. The efferent and afferent arterioles are both constricted. b. The efferent and afferent arterioles are both dilated. c. Only the afferent arteriole is constricted. d. Only the efferent arteriole is constricted. e. The afferent arteriole is constricted and the efferent arteriole is dilated.

396. The answer is b.

397. A 47-year-old woman presents for her annual physical examination. A year ago, the patient started a diet and exercise regimen when her blood pressure was 130/85 mm Hg. She has lost 10 lb and reduced her BMI to 25 kg/m2 , but her blood pressure on this visit is found to be 145/98 mm Hg. The patient is started on a combination of a low dose of hydrochlorothiazide with the K+ -sparing diuretic, triamterene. The amount of potassium excreted by the kidney will decrease if which of the following occurs? a. Circulating aldosterone levels increase. b. Dietary intake of potassium increases. c. Distal tubular flow increases. d. Na+ reabsorption by the distal nephron decreases. e. The excretion of organic ions decreases.

397. The answer is d.

398. A 23-year-old woman presents with burning epigastric pain. A careful history reveals that the burning is exacerbated by fasting and improved with meals. The woman is prescribed the H2 -receptor antagonist, cimeti-dine, for suspected peptic ulcer disease. Cimetidine may also have an adverse effect on proximal tubular function. Which of the following substances is more concentrated at the end of the proximal tubule than at the beginning of the proximal tubule? a. Bicarbonate b. Creatinine c. Glucose d. Phosphate e. Sodium

398. The answer is b.

399. A 69-year-old man with chronic hypertension presents to his physician's office. His blood pressure is 165/105 mm Hg despite treatment with a diuretic, β- blocker, and an angiotensin receptor antagonist. It is decided that a fourth drug is needed for the patient's resistant hypertension, and he is prescribed the vasodilator diltiazem, a calcium channel antagonist. The effect of decreasing the resistance of the afferent arteriole in the glomerulus of the kidney is to decrease which of the following aspects of renal function? a. Filtration fraction b. Glomerular filtration rate c. Oncotic pressure of the peritubular capillary blood d. Renal plasma flow e. Renin release from juxtaglomerular cells

399. The answer is e.

400. A 17-year-old male presents with fatigue, muscle cramps, and joint pain. Blood analysis reveals hypokalemia, hypomagnesemia, and hypochloremic metabolic alkalosis, and urinalysis reveals decreased urinary chloride and calcium. The clinical findings suggest a loss-of-function mutation of the SLC12A3 gene encoding the thiazide-sensitive sodium-chloride cotransporter (NCCT). Electrically neutral active transport of sodium and chloride occurs in which of the following areas of the nephron? a. Cortical collecting duct b. Descending limb of the loop of Henle c. Distal tubule d. Medullary collecting duct e. Thin ascending limb of the loop of Henle

400. The answer is c.

401. A 36-year-old African American man presents with low renin essential hypertension. Renin release from the juxtaglomerular apparatus is normally inhibited by which of the following? a. Aldosterone b. β-Adrenergic agonists c. Increased pressure within the afferent arterioles d. Prostaglandins e. Stimulation of the macula densa

401. The answer is c.

402. A 44-year-old woman presents with abdominal pain, fever, and chills. Physical examination reveals costovertebral angle tenderness, previously undiagnosed hypertension, and a mid-systolic click. Urine culture shows bacteriuria and free water clearance is positive, indicating excretion of dilute urine. The ability of the kidney to excrete concentrated urine will increase if which of the following occurs? a. The activity of the Na+-K+ pump in the loop of Henle increases. b. The flow of filtrate through the loop of Henle increases. c. The glomerular capillary pressure increases. d. The permeability of the collecting duct to water decreases. e. The reabsorption of Na+ by the proximal tubule decreases.

402. The answer is a.

403. A patient undergoing surgery develops an increase in the secretion of ACTH, cortisol, and aldosterone. Which of the following statements best characterizes the actions of aldosterone in the kidney? a. It increases hydrogen ion reabsorption from the distal convoluted tubules. b. It increases potassium ion reabsorption from the distal convoluted tubules. c. It increases sodium ion reabsorption in the proximal tubule. d. It increases the number of active epithelial sodium channels (ENaCs) in the collecting ducts. e. It produces its effect by activating cyclic adenosine monophosphate (cAMP).

403. The answer is d.

404. A 44-year-old African American woman with a medical history of hypertension and diabetes mellitus presents to the clinic for her routine examination. At her last visit, her blood pressure was 150/95 despite trying to control her blood pressure with diet and exercise, so the patient was placed on lisinopril. She also takes metformin for her diabetes. Today, the patient's blood pressure has decreased to 130/80. Routine laboratory work indicates that she has a blood glucose of 120 mg/dL, serum creatinine of 1.0 mg/dL, and urinary microalbumin of <30 mg. What effect does angiotensin II have on the glomerular filtration rate (GFR)? a. Decreases GFR because of constriction of the afferent arteriole b. Decreases GFR because of dilation of the efferent arteriole c. No change in GFR because of equal constriction of the afferent and efferent arteriole d. Increases GFR because of dilation of the afferent arteriole e. Increases GFR because of constriction of the efferent arteriole

404. The answer is e.

406. A trauma patient with multiple rib fractures requires intubation and mechanical ventilation. Mechanical ventilation causes an increase in the patient's vasopressin secretion and plasma levels. Which of the following is the effect of vasopressin on the kidney? a. Increased diameter of the renal artery b. Increased glomerular filtration rate c. Increased excretion of Na+ d. Increased excretion of water e. Increased permeability of the collecting ducts to water

406. The answer is e.

407. A 16-year-old pregnant girl is admitted to the hospital in labor. Her blood pressure is 130/85 mm Hg, and her plasma creatinine is 2.7 mg/dL (normal 0.6 to 1.2 mg/dL). Renal ultrasonography demonstrates severe bilateral hydronephrosis. Which of the following is the most likely cause of this patient's high creatinine levels? a. Coarctation of the renal artery b. Hypovolemia c. Hyperproteinemia d. Increased sympathetic nerve activity e. Ureteral obstruction

407. The answer is e.

409. A patient with chronic obstructive lung disease and cor pulmonale is given acetazolamide to inhibit carbonic anhydrase, along with a thiazide diuretic. How does the distal nephron differ functionally from the proximal tubule? a. The distal nephron has a more negative intraluminal potential than the proximal tubule. b. The distal nephron is less responsive to aldosterone than the proximal tubule. c. The distal nephron is more permeable to hydrogen ion than the proximal tubule. d. The distal nephron secretes more hydrogen ion than the proximal tubule does. e. The distal nephron secretes less potassium than the proximal tubule does.

409. The answer is a.

410. An 82-year-old man who recently suffered head trauma from a car accident presents with polyuria and polydipsia. Blood analysis reveals hypernatremia and urinalysis shows hypotonicity and an increased free water clearance. In which of the following conditions is an increased free water clearance a hallmark of the disease? a. Diabetes insipidus b. Diabetes mellitus c. Diuretic therapy d. Heart failure e. Renal failure

410. The answer is a.

411. A 58-year-old man is hospitalized following an acute myocardial infarction. Several days later, the patient's 24-hour urine output is lower than normal. An increase in which of the following contributes to a reduced urine flow in a patient with congestive heart failure and reduced effective circulating volume? a. ANP b. Renal natriuretic peptide (urodilatin) c. Renal perfusion pressure d. Renal sympathetic nerve activity e. Sodium delivery to the macula densa

411. The answer is d.

412. A 58-year-old man presents with hematuria, abdominal pain, and fatigue. Physical examination reveals a flank mass and an abdominal CT reveals a large solid mass on the left kidney. Laboratory studies show anemia and increased creatinine and BUN suggestive of advanced disease. A decrease in GFR would result from which of the following? a. A decrease in the concentration of plasma protein b. An increase in afferent arteriolar pressure c. An increase in RBF d. Compression of the renal capsule e. Constriction of the efferent arteriole

412. The answer is d.

413. A patient has suffered from persistent diarrhea lasting for 7 days. Which of the following would be decreased in this patient? a. Anion gap b. Filtered load of HCO3 c. H+ secretion by the distal nephron d. Production of ammonia by the proximal tubule e. Production of new bicarbonate by the distal nephron

413. The answer is b.

414. A 27-year-old graduate student from China presents at the Student Medical Center for mandatory tuberculosis screening. Quantiferon testing is positive and physical examination reveals cough, cachexia, and mild respiratory distress. Chest x-ray reveals a cavitary lesion in the right upper lobe. Blood analysis reveals a serum sodium of 118 mg/dL and an increased ADH concentration. As a result, the permeability of the collecting duct will be increased to which of the following? a. Ammonium ion b. Hydrogen ion c. Potassium ion d. Sodium ion e. Urea

414. The answer is e.

415. A 54-year-old woman presents with profound fatigue, ankle edema, and paroxysmal nocturnal dyspnea. Filtration fraction may be increased in patients with heart failure due to an increase in which of the following? a. Afferent arteriolar resistance b. Efferent arteriolar resistance c. Hydrostatic pressure within Bowman capsule d. Plasma oncotic pressure e. Renal blood flow

415. The answer is b.

416. A 29-year-old man expresses concern about his upcoming skiing trip to Breckenridge, Colorado (elevation = 10,000 ft). He states that every time he goes there, he gets high altitude sickness that is relieved when he is given oxygen. The family physician gives the patient a prescription for oxygen to use when he arrives in Colorado, as well as a prescription for acetazolamide to take for 2 days prior and throughout his 4-day trip. Carbonic anhydrase inhibitors exert their diuretic effect by inhibiting the reabsorption of Na + in which of the following parts of the nephron? a. The proximal tubule b. The thick ascending limb of loop of Henle c. The distal convoluted tubule d. The cortical collecting duct e. The outer medullary collecting duct

416. The answer is a.

417. A patient with atherosclerosis shows signs of chronic renal failure attributed to poor renal perfusion and ischemic necrosis of the nephrons. Which of the following endogenous substances causes RBF to decrease? a. Acetylcholine b. Angiotensin II c. ANP d. Dopamine e. Nitric oxide

417. The answer is b.

418. A 19-year-old man presents for his annual football physical examination. He is asymptomatic but urinalysis reveals macroscopic hematuria. Microscopic examination is positive for deformed erythrocytes and RBC casts. Where in the renal-urinary system is the most likely origin of the blood in his urine? a. Bowman capsule b. Glomerulus c. Peritubular capillaries d. Renal artery e. Urinary bladder

418. The answer is b.

419. A 55-year-old hypertensive patient is placed on a potassium-sparing diuretic. Which of the following mechanisms of action are characteristic of potassium- sparing diuretics? a. Inhibition of H+ secretion in the proximal tubule b. Inhibition of Na-Cl cotransport in the early portion of the distal tubule c. Inhibition of Na-K-2Cl cotransport in the medullary thick ascending limb of loop of Henle d. Inhibition of Na+ reabsorption via Na channels in the collecting tubules e. Inhibition of vasopressin secretion

419. The answer is e.

420. Which of the following statements best describes renal ammonia (NH3)? a. NH3 is classified as a titratable acid. b. NH3 excretion reduces the concentration of bicarbonate in the plasma. c. Renal NH3 synthesis is decreased in hyperkalemia. d. The majority of NH3 is produced by epithelial cells in the distal nephron. e. The tubular epithelial cells are impermeable to NH3

420. The answer is c.

421. In type IV RTA, the excretion of which of the following urinary electrolytes is increased? a. Cl− b. H+ c. K+ d. Na+ e. NH4

421. The answer is d.

422. A patient with renal failure presents to the clinic with increasing fatigue for the past month. Based on a thorough history and physical, as well as diagnostic testing, it is determined that the symptoms are caused by the loss of a hormone produced by the kidney. Which of the following is the most likely diagnosis? a. Acidosis b. Anemia c. Edema d. Hypertension e. Uremia

422. The answer is b.

423. A patient with congestive heart failure presents with jugular venous distention, ascites, and peripheral edema. Blood work shows elevated levels of plasma ANP. ANP increases Na+ excretion by which of the following mechanisms? a. Contracting afferent arterioles b. Decreasing GFR c. Decreasing sodium reabsorption by the inner medullary collecting duct d. Increasing permeability of the apical membrane of the collecting duct epithelial cells e. Increasing sodium reabsorption by the proximal tubules

423. The answer is c.

424. An elderly woman presents with spiking fever, shaking chills, nausea, and costovertebral angle tenderness. Urine cultures are positive and she is hospitalized for pyelonephritis. Her glomerular filtration rate (GFR) decreases with a resultant increase in the concentration of NaCl delivered in the intraluminal fluid to the thick ascending limb of the loop of Henle. Under these conditions, the macula densa will increase the formation and release of which of the following substances? a. Adenosine b. Aldosterone c. Angiotensinogen d. Antidiuretic hormone (ADH) e. Renin

424. The answer is a.

426. A 39-year-old man presents with severe writhing back pain, hematuria, and nausea. An intravenous pyelogram confirms a diagnosis of renal calculi. The presence of strongly opaque stones on the plain film is suggestive of calcium oxalate stones, which have an increased incidence with hypophosphatemia. The renal clearance of phosphate is increased by which of the following hormones? a. Aldosterone b. Angiotensin c. Norepinephrine d. Parathyroid hormone (PTH) e. Vasopressin

426. The answer is d.

427. A 41-year-old woman presents with hemoptysis and hematuria. Laboratory findings include markedly elevated BUN, creatinine, and erythrocyte sedimentation rate. Serum is positive for antiproteinase-3 ANCA, and negative for antiglomerular basement membrane antibody, suggesting Wegener granulomatosis rather than Goodpasture disease. Urinalysis reveals proteinuria and RBC casts, in addition to the hematuria. Progressive renal failure makes it difficult for the patient to excrete a normal dietary potassium load. Which of the following will produce the greatest increase in potassium secretion? a. A decrease in circulating blood volume b. A decrease in renal blood flow c. A decrease in urine flow rate d. An increase in distal nephron sodium concentration e. An increase in sympathetic nerve activity

427. The answer is d.

428. A 36-year-old man suffers third-degree burns over 70% of his body while responding to a three-alarm fire. His effective circulating volume and renal perfusion pressure drop precipitously and the concentration of NaCl in the intraluminal fluid in the kidney decreases. These conditions cause the juxtaglomerular apparatus to release which of the following hormones? a. Adenosine b. Aldosterone c. Angiotensinogen d. ADH e. Renin

428. The answer is e.

429. Renal and pulmonary biopsies in a 35-year-old woman with Wegener's granulomatosis demonstrate glomerulonephritis and a granulomatous vasculitis in the lungs. In adults, which of the following is greater in the pulmonary circulation compared to the renal circulation? a. Arterial pressure b. Blood flow c. Capillary hydrostatic pressure d. Capillary oncotic pressure e. Vascular resistance

429. The answer is b.

430. A 65-year-old man presents in the emergency department with a fracture of his right arm after slipping and falling on the ice. He reports that he has had back pain for the past 6 months. Blood results show Hb = 9 g/dL; hematocrit = 30%; BUN = 35 mg/dL; creatinine = 3 mg/dL. Urinalysis shows pH >5.3 and is positive for Bence Jones proteins. The patient is diagnosed with type II (proximal) RTA secondary to multiple myeloma. The transport of H + into the proximal tubule is primarily associated with which of the following? a. Excretion of ammonium ion b. Excretion of potassium ion c. Reabsorption of bicarbonate ion d. Reabsorption of calcium ion e. Reabsorption of phosphate ion

430. The answer is c.

431. A 57-year-old woman with chronic cardiac failure presented at the University Medical Center to participate in a clinical research study on the genetics of heart failure. Genetic analysis showed an increase in ADH gene expression and associated hypothalamic biosynthesis of the hormone, in addition to increased release of the hormone from the posterior pituitary. In the presence of ADH, the filtrate will be isotonic to plasma in which part of the kidney? a. Ascending limb of the loop of Henle b. Descending limb of the loop of Henle c. Cortical collecting tubule d. Medullary collecting tubule e. Renal pelvis

431. The answer is c.

432. A hypertensive patient develops chronic renal failure from progressive nephrosclerosis. Which of the following is associated with chronic renal failure? a. A decrease in the excretion of creatinine b. A decrease in the fractional excretion of sodium c. A decrease in net acid excretion d. An increase in free water clearance e. A normal anion gap

432. The answer is a.

433. A 65-year-old male with a past medical history of COPD, hypertension, diabetes mellitus type II, and hypercholesterolemia presents to the emergency department with swelling of the legs and feet and shortness of breath. After complete history, physical exam, and appropriate diagnostic testing, it is determined that the patient is experiencing volume overload as a result of an acute exacerbation of congestive heart failure. The patient is started on oxygen therapy, nebulizer treatments, and intravenous furosemide, which increases sodium reabsorption in the thin ascending limb of the loop of Henle via which of the following mechanisms? a. Na+Cl− cotransport b. Na+/H+ exchange c. Na+/K+exchange d. Na+− K+− 2Cl− cotransport e. Na+/nutrient cotransport

433. The answer is d.

434. A 28-year-old woman with blood pressures that have ranged from 155-190/70-100 during her last two visits to her family physician is started on lisinopril. When her blood pressure worsened on lisinopril, she was referred to a nephrologist for uncontrolled hypertension. Her blood pressure was 170/95 and a renal ultrasound showed a greater than 50% reduction in vessel diameter. Based on the laboratory data shown below, what is her estimated renal blood flow? Serum inulin = 2 mg/dL Urinary inulin = 10 mg/mL Serum PAH = 6 mg/dL Urinary PAH = 20 mg/mL Urine flow = 1.2 mL/min Hematocrit = 40% Hemoglobin = 13 a. 400 mL/min b. 600 mL/min c. 667 mL/min d. 1000 mL/min e. 1250 mL/min

434. The answer is c

The occurrence of hypocalcemia can have dire consequences for numerous physiologic processes. The kidney plays a major role in maintaining calcium balance during hypocalcemic states by decreas- ing calcium excretion. The major mechanism underlying the response of the kidney during hypocalcemia is which of the following? A. Parathyroid hormone-induced stimulation of calcium reabsorp- tion by the thick ascending limb B. Fluid flow-induced stimulation of calcium reabsorption by the collecting duct C. Calcitonin-induced inhibition of calcium secretion by the distal convoluted tubule D. Vitamin D-induced activation of calcium reabsorption by the proximal tubule

A. The occurrence of low plasma calcium levels is sensed by a calcium receptor on the surface of the parathyroid gland, leading to stimulation of synthesis and secretion of parathyroid hormone. PTH, along with vitamin D and to a lesser extent calcitonin, plays a dominant role in regulating calcium balance. In the kidney, PTH has diverse actions, but its key action appears to be to promote calcium reabsorption. The key sites regulating calcium reabsorption are the thick ascending limb and the distal convoluted tubule.

Increases in both renal blood flow and GFR are caused by which of the following? A Dilation of the afferent ateioles B Increased glomeular capillay filtration coefficient C Increased plasma colloid osmotic pressure D Dilation of the efferent ateioles E Increased blood viscosity due to increased hematocit

A: Dilation of the afferent arteioles

The urine of a pt with DECREASED GFR, will be____________ A More dilute B More concentrated C Unchanged D Blue

A More dilute if GFR is low → volume of filtrate is low → fluid is going to move through renal tubule SLOWLY → provides more access and more time for solute to be resorbed

Which part of the nephron is targeted by thiazide diuretics such as chlothalidone? A The early distal convoluted tubule Na/Cl co-transpoter) B The thick ascending loop of Henle Na/K/2Cl cotranspoter) C The late distal convoluted tubule Na/K countetranspoter) D The proximal convoluted tubule Na/K countetranspoter)

A is correct A - The early DCT is the target for thiazides, which decreases Na reabsorption. B - the loop of henle is the target for loop diuretics such as furosemide Lasix). C - The late DCT is the target for aldosterone antagonists such as spironolactone. ACEs and ARBs also indirectly affect the DCT by decreasing aldosterone production. D - The PCT is the site of action for carbonic anhydrase inhibitors such as acetazolamide

An individual is known to be suffering from diabetes mellitus. Recently, he has developed hypertension. His doctor suspects that the patient may be developing renal insufficiency that is leading to a reduced glomerular filtration and, as a result, hypervolemia and hyper-tension. The doctor wishes to evaluate kidney function by measuring the glomerular filtration rate (GFR). She can estimate GFR best by per-forming a urine clearance study of which of the following substances? A. Creatinine B. Para-aminohippuric acid (PAH) C. Urea D. Glucose E. Sodium

A. Creatinine is a normal end product of muscle metabolism. It is freely filtered at the glomerulus and excreted in the urine. Although creatinine is not reabsorbed by the kidney tubules, it is partially secreted so that the rate of urinary excretion of creatinine overestimates the rate of filtration by a small percentage in healthy individuals (it overestimates more in individuals with a compromised GFR). Nonetheless, in the clinic the clearance of creatinine can provide a reasonable estimate of GFR.

A student under stress has been feeling light-headed, especially after standing, and has developed a brisk diuresis. He has the smell of ace-tone on his breath. Upon admission to the emergency room, he is diagnosed with diabetic ketoacidosis, which is accompanied by extreme hypovolemia, supposedly because of the brisk diuresis. The brisk diuresis is a consequence of which of the following? A. High levels of glucose in the tubular fluid/urine B. Increased glomerular filtration rate C. Suppression of arginine vasopressin secretion D. Suppression of aldosterone secretion E. Decreased angiotensin II plasma levels

A. In diabetic ketoacidosis, plasma levels of glucose are elevated, leading to an excess filtered load of glucose. The increased rate of filtration of glucose can exceed the capacity of the Na+-glucose cotransporter in the proximal tubule to reabsorb all the glucose. The excess glucose that is not reabsorbed will be retained in the tubular lumen and generate a solute diuresis.

Which of these is a false statement? A JGA is responsible for the release of renin B Angiotensin I is directly responsible for reabsorption of salt and water C ADH increase the number of aquapoins in the collecting duct D Atial natiuretic peptide works in the opposite of Aldosterone E None of the above

B. Aldosterone release is activated by Angiotensin II which is conveted from Angiotensin I. Aldosterone is directly responsible for reabsorption of salt and water. Aldosterone is activated by Angiotensin II which was conveted from Angiotensin I (by ACE in lungs).

A 35-year-old female is noted to have new-onset hypertension that is thought to be due to an aldosterone-secreting adrenal tumor. Which of the following is likely to be seen in this patient? A. Hypertension markedly improved with furosemide B. Elevated serum sodium level C. Elevated serum potassium level D. Elevated urinary cortisol level

B. Aldosterone-secreting tumors may lead to hypertension, usually causing elevated serum sodium levels and low potassium levels (because of urinary reabsorption of sodium and excretion of potassium). One of the basic tests in the workup of newly diagnosed hypertension is serum electrolytes to assess for this disorder.

A 37-year-old man is stabbed in the arm and chest in a bar fight and experiences an estimated blood loss of 1000 mL. His blood pressure is 100/50 mm Hg, and his heart rate is 110 beats per minute. Which of the following describes this patient's physiologic response? A. β-Adrenergic stimulation of the vasculature B. Vasoconstriction to the renal afferent and efferent arterioles C. Reduction of ADH release D. Lowering of urine osmolality

B. Hypovolemia triggers several responses, including sympathetic mediated vasoconstriction to renal afferent and efferent arterioles, which decrease GFR. Meanwhile, ADH release induces more concentrated urine (retention of free water), and aldosterone induces sodium retention.

An individual has adult-onset diabetes. She has high levels of glucose in the urine and is experiencing a brisk diuresis. The appearance of glucose in the urine is a consequence of which of the following processes in the proximal tubule? A. Inhibition of Na+-K+-ATPase (Na+ pump) B. Saturation of the Na+-glucose cotransporter C. Saturation of the Na+-H+ exchanger D. Stimulation of glucose secretion E. Stimulation of glycogen breakdown

B. In diabetes mellitus, in which plasma glucose levels are markedly elevated, the high glucose load being filtered (with an elevated concentration) can exceed the capacity of the luminal Na+-glucose cotransporter to reabsorb glucose (ie, the carrier is saturated). The excess glucose that is not reabsorbed is trapped in the tubular fluid because no transport pathways are present in later nephron segments to reabsorb this hexose. Hence, glycosuria will develop.

A 23-year-old man is brought into the emergency center because of cocaine intoxication. His urine is "tea" colored as a result of breakdown of skeletal muscle by the cocaine, so-called rhabdomyolysis. Which of the following describes the fate of myoglobin in the renal tubule? A. Absorbed in the proximal tubule by active transport by sodium cotransport B. Absorbed in the proximal tubule by receptor-mediated endocytosis C. Absorbed in the distal tubule by facilitated diffusion D. Not absorbed and excreted in the urine

B. Larger peptides and proteins such as myoglobin and albumin bind to the luminal membrane and enter the cell by receptor-mediated endocytic processes and are delivered to lysosomes for degradation. Myoglobin, if crystallized in the renal tubules, can lead to a toxic effect, sometimes even renal failure. Cocaine can induce numerous toxic effects, including rhabdomyolysis. Intravenous hydration is important to increase the solubility of the myoglobin.

A new patient is complaining about having to micturate numerous times during the day and being forced to get up multiple times throughout the night. Her diet has not changed, but she complains of being fatigued throughout the day (and frustrated with her shortened sleep periods). When she moves from a supine to an erect position, her blood pressure is observed to decrease modestly and her heart rate increases slightly. Blood chemistries reveal that she is modestly hypernatremic, and plasma arginine vasopressin and renin levels are markedly elevated. Urinalysis revealed copious diluted urine. The patient most likely has which of the following conditions? A. Central diabetes insipidus B. Nephrogenic diabetes insipidus C. Psychogenic polydipsia D. Excessive consumption of alcohol E. Brain trauma

B. Nephrogenic diabetes insipidus (nephrogenic DI) is a relatively rare disease that arises from defective water channels (aquaporins) or pathways regulating the water channels in the collecting ducts. It is characterized by high levels of ADH in the plasma and excretion of copious diluted urine. This contrasts with central diabetes insipidus, the more common form of DI, which is characterized by low synthesis and secretion of vasopressin from the posterior pituitary, giving rise to low levels of vasopressin in the plasma, but with the effect on urinary excretion being the same.

After a rapid ascent to very high altitude, one begins to hyperventilate because of hypoxic drive. The hyperventilation will cause a decrease in the arterial PCO2 . What is the renal response to this condition? A. Increased rate of acid excretion B. Decreased rate of acid excretion C. Increased rate of bicarbonate reabsorption D. Diuresis to eliminate excess fluid E. Increased ammoniagenesis

B. The two most important drivers of renal bicarbonate reabsorption are CO2 and H+. The hyperventilation experienced at high altitude decreases the PCO2, which generates a respiratory alkalosis. Reducing both CO2 and H+ will decrease renal H+ secretion and thus bicarbonate reabsorption. The filtered bicarbonate load will exceed the rate of H+ secretion with a loss of excess bicarbonate in the urine.

A 24-year-old man was admitted to the emergency department and complained of abdominal pain, dizziness when standing, and nausea leading to occasional vomiting. The patient's blood pressure was low, and his heart rate was elevated. Laboratory tests revealed a reduced hematocrit, hypoalbuminemia, very modest hyponatremia, and ele- vated creatinine, blood urea nitrogen (BUN), and renin levels. Urine output was minimal. The patient informed the physician that he had been taking extra aspirin recently to alleviate back pain. Which of the following is the most like diagnosis? A. Episodes of vomiting leading to hypovolemia B. Gastrointestinal bleeding leading to hypovolemia C. Diarrhea leading to hypovolemia D. Cirrhosis of the liver E. Nephrotic syndrome accompanied by excretion of protein

B. This patient probably has gastrointestinal bleeding caused by sensitivity to aspirin. It is well known that aspirin can induce erosions in the gastrointestinal lining that can lead to bleeding ulcers. The bleeding will lead to loss of blood and hypovolemia that causes a decrease in capillary pressure and, as a result, a shift of fluid from the interstitial space into the vasculature. This fluid shift is apparent from the decrease in hematocrit and dilution of plasma proteins (hypoalbuminemia).

A 56-year-old woman is diagnosed with small-cell carcinoma of the lung. She has a paraneoplastic effect from the cancer, with release of an ADH-like agent. Which of the following is most likely to be seen? A. Elevated serum sodium B. Elevated serum osmolarity C. Elevated urine sodium D. Elevated urine catecholamines

C. ADH allows for increased reabsorption of water from the collecting system, and thus decreases serum sodium and serum osmolarity. The urine is concentrated with high sodium and high osmolarity.

A hypertensive patient was prescribed the diuretic Lasix (furosemide) to increase urinary output. Furosemide, a "high-ceiling" diuretic, is a potent agent because it binds to and inhibits which of the following transport processes? A. The Na+-glucose cotransporter in the proximal tubule B. The Na+-K+ exchange pump in all nephron segments C. The Na+-K+-Cl− cotransporter in the thick ascending limb D. The Na+-Cl− cotransporter in the distal convoluted tubule E. The Na+ channel in the cortical collecting duct

C. Furosemide inhibits the Na+-K+-Cl− cotransporter in the thick ascending limb. This is a critical transporter for reabsorption of NaCl from the thick ascending limb into the medullary interstitium. This transport of NaCl is the driving force behind the establishment of the hypertonicity of the medullary interstitium that is essential for the reabsorption of water from the collecting ducts and the generation of a concentrated urine. Inhibition of the thick ascending limb cotransporter will lead to both a greater load of NaCl left behind in the tubular fluid, increasing urinary NaCl levels, and a reduced hypertonicity of the medullary interstitium (less NaCl), decreasing the gradient for water reabsorption from the collecting ducts. This leads to a rapid and sustained increase in urinary volume flow along with significant urinary levels of NaCl. Hence, furosemide is a potent diuretic.

A 56-year-old woman receives chemotherapy for ovarian cancer and develops hypomagnesemia as a result. Urine chemistries reveal a large amount of magnesium in the urine. Which of the following areas most likely was affected by the chemotherapeutic agent? A. Proximal tubule B. Descending loop C. Ascending loop D. Convoluted distal tubule E. Collecting duct

C. The majority of magnesium is resorbed in the thick ascending limb of the renal tubule.

Recovery from a severe metabolic acidosis is most dependent on which of the following? A. The rate of ventilation to blow off excess CO2 B. The rate of H+ secretion by the kidney C. The rate of H+ excretion by the kidney D. The arterial pH E. The arterial PCO2

C. The rate of recovery from a severe metabolic acidosis is most dependent on the rate of H+ excretion. Pulmonary compensation occurs rapidly; however, it can only minimize the change in pH. Pulmonary compensation cannot restore the balance after a metabolic disturbance. Recovery necessitates the excretion of the entire acid load to the system. Renal acid excretion is limited by the availability of titratable acids and ammonia for ammonium ion formation from secreted H+. The primary adaptive response of the kidney to an acidosis is ammoniagenesis. Ammoniagenesis can augment the daily excretion of acids as much as threefold. When an equivalent amount of acid is excreted, acid-base balance will be restored.

Regarding how the renal system acts as a buffering system, which of these is a false statement? A Removal (secretion) of H through uine B Generation of new bicarb C Resoption of filtered bicarb D Excretion of CO2 E None of the above

D Excretion of CO2

Which of the following is a true statement? A Renin is released by the JG cells when it senses high blood pressure B Angiotensin conveting enzyme is found pimaily in the kidneys C Aldosterone acts on the intercalated cells D Angiotensin II acts on the proximal tubule E None of the above

D is correct A - false, Renin is released when there is low blood pressure (hypovolemia) B - false, ACE is found and pimaily made in the lungs. C - false, Aldosterone acts on the pincipal cells D - Corect answer - Angiotensin II acts on the proximal tubule to increase NA & H2O reabsorption

A hypertensive patient is prescribed a loop diuretic such as Lasix without any supplements. One week later, the patient returns to the clinic complaining of dizziness, weakness, and nausea. The most likely cause of the patient's worsening condition is the development of which of the following? A. Metabolic acidosis B. Hyponatremia C. Hypercalcemia D. Hypokalemia E. Hypovolemia

D. Loop diuretics such as Lasix (furosemide) potently inhibit the Na+-K+-Cl− cotransporter in the thick ascending limb. NaCl reabsorption in the thick ascending limb through this cotransporter is the driving force behind the operation of the countercurrent multiplierand the ability to excrete a concentrated urine (and a diluted urine). Inhibition of this cotransporter leads to a much greater load of Na+ being delivered to the distal tubule and collecting ducts. With the increased delivery of Na+ and fluid to the late distal tubule and cortical collecting ducts, K+ secretion by the late distal tubule and cortical collecting ducts will be enhanced, leading to hypokalemia.

A 34-year-old woman feels compelled to drink water "all the time." She does not drink Gatorade or other solute drinks but takes pure water. Her serum sodium is low, as is her serum osmolality. The physician is unsure whether this patient has psychogenic water intoxication versus diabetes insipidus. Which of the following would reliably differentiate between these two disorders? A. Urinary electrolytes compared with serum electrolytes B. Urinary osmolality compared with serum osmolality C. Serum ADH levels D. Restriction from drinking water

D. Psychogenic water intoxication has the appearance of diabetes insipidus. Owing to the marked hypotonic fluid ingestion, the body attempts to excrete free water, and thus ADH secretion is inhibited. Both serum and urine sodium and osmolality are very low. However, in psychogenic water intoxication, when water is restricted, the body will produce ADH eventually, leading to normalization of the serum osmolality and concentration of urine. In diabetes insipidus, because of a problem with ADH production and secretion, even with water restriction the patient will produce very dilute urine and will not be able to concentrate the urine.

A student in a clinical study had her normal diet changed to a diet high in potassium, but everything else was unremarkable. The student noted that she had gained nearly 2 lb within a few days after starting the diet. Laboratory tests indicated a modest elevation in plasma K+ but no change in plasma Na+ levels. Interestingly, plasma levels of arginine vasopressin and renin were depressed, results consistent with volume expansion. What is the most likely reason for the hypervolemia? A. Increased plasma protein oncotic pressure leading to fluid retention B. Decreased glomerular filtration rate leading to fluid retention C. Stimulation of the renin-angiotensin-aldosterone system leading to Na+ and water retention D. Stimulation of aldosterone secretion by the high-K+ diet leading to Na+ and water retention E. Decreased ANP release leading to fluid retention

D. The consumption of a diet high in K+ will lead to K+ loading, which is known to stimulate directly the secretion of aldosterone from the adrenal gland. The elevated aldosterone will stimulate the synthesis of new Na+-K+ exchange pumps and luminal membrane Na+ channels in the renal cortical collecting ducts, leading to stimulation of Na+ (and Cl−) reabsorption and fluid retention (K+ secretion also is stimulated). The salt and fluid retention will lead to volume expansion as made evident by a gain in weight. Secondarily, the volume retention will be sensed by volume receptors, leading to a depression in the sympathetic nervous activity, a decrease in arginine vasopressin release, and a decrease in renin release. Hence, the K+-induced stimulation of aldosterone secretion completely bypasses a role for the renin-angiotensin-aldosterone axis in this setting.

A 56-year-old patient has chronic renal failure that results in fewer functioning nephrons. The patient's dietary intake of potassium has not changed, and this could lead to dangerous hyperkalemia in the face of fewer functioning nephrons. However, because of adaptive responses to the potassium load, plasma potassium is noted to rise only slightly (< 0.5 mEq/L). Although numerous renal and extrarenal responses may underlie this K+ adaptation, what is the dominant adaptive response of the kidney to maintain plasma K+ levels in this chronic condition? A. Increased glomerular filtration leading to increased filtration of K+ B. Increased expression of Na+-K+ exchange pumps in the proximal tubule leading to enhanced K+ secretion C. Decreased expression of the Na+-K+-Cl− cotransporter in the thick ascending limb leading to reduced K+ reabsorption D. Increased expression of Na+-K+ exchange pumps in the cortical collecting tubule leading to enhanced K+ secretion E. Decreased recycling of K+ from the outer medullary collecting duct to the thin descending limb giving rise to enhanced K+ excretion

D. The continuous ingestion of a constant potassium load in the face of a reduced number of functioning nephrons leads to a chronic overload of K+, but without the development of extreme hyperkalemia. The kidney slowly adapts to the increased potassium load in a process called K+ adaptation, which leads to a kaliuresis caused by an enhanced rate of K+ secretion by the late distal tubule and cortical collecting tubule (the early part of the outer medullary collecting duct also may participate). This enhanced K+ secretion arises from both a direct effect of the elevated plasma K+ on the expression of new Na+-K+ exchange pumps at the basolateral membrane in these segments and an indirect effect through K+ -induced stimulation of aldosterone secretion from the adrenal gland.

A 21-year-old man with gastroenteritis developed severe vomiting with a loss of stomach acids. A metabolic alkalosis is present. Which of the following is most likely to occur? A. The plasma bicarbonate concentration will decrease. B. H+ will move from the plasma into the cells. C. Peripheral chemoreceptors will stimulate pulmonary ventilation. D. Renal H+ excretion will decrease.

D. The loss of gastric (hydrochloric) acid leads to an increase in the plasma bicarbonate concentration and a metabolic alkalosis. The increase in the pH will depress peripheral chemoreceptors to slow ventilation and increase the PCO2 to compensate for the increased bicarbonate. The increase in PCO2 will bring the pH nearer to 7.4 and at the same time increase renal H+ secretion. Because there is an increased level of bicarbonate in the glomerular filtrate, there will be an increase in bicarbonate reabsorption. The rate of filtration will exceed the rate of H+ secretion, and there will be a continuous loss of bicarbonate. As the plasma bicarbonate falls, the pH will continue to approach the normal of 7.4 and the ventilatory rate will increase gradually. When all the excess bicarbonate has been excreted, the plasma bicarbonate and pH will have returned to normal with a normal respiratory rate.

Which of these is true regarding the collecting ducts A Responsible for finalization of uine B Where the effects of ADH occur C A site of resorption D Regulation of acid/base E All of the above

E All of the above

If an individual becomes hypovolemic, such as during periods of diar- rhea or excessive sweating, plasma ADH, or arginine vasopressin, levels are elevated rapidly and urine volume is decreased (antidiure- sis). This effect of ADH on water excretion predominantly occurs in the collecting ducts by ADH-induced activation/inhibition of which of the following steps/processes? A. Inhibition of sodium reabsorption B. Activation of potassium secretion C. Increased leakiness of the collecting duct to water and solute D. Insertion of sodium channels in the luminal membrane E. Insertion of aquaporin channels in the luminal membrane

E. A key step in regulating water reabsorption in the collecting ducts is controlling the insertion and removal of aquaporins (water channels) at the luminal cell membrane. In the presence of ADH, ADH binds to a V2 vasopressin receptor on the basolateral membrane of the cells, leading to production of cAMP and the protein kinase A-induced phosphorylation of intracellular aquaporin channels retained in cytoplasmic vesicle pools. The phosphorylation leads to the insertion of the vesicles, along with the aquaporins, into the luminal membrane, thereby increasing the water permeability of the luminal membrane.

A 21-year-old man has been vomiting to the point where he has become hypovolemic, as evidenced by an accompanying decrease in blood pressure and a feeling of light-headedness. The kidneys respond by reducing urinary volume flow, thus limiting the potential extent of hypovolemia. Increases in the plasma levels of which of the following hormones will bring about the most dramatic decrease in urinary volume flow rate? A. Angiotensin II B. Atrial natriuretic peptide C. Parathyroid hormone D. Aldosterone E. Arginine vasopressin (ADH)

E. Increases in plasma levels of arginine vasopressin, or ADH, lead to water reabsorption by the collecting ducts, decreasing urine output.

384. A 63-year-old woman is brought to the emergency department complaining of fatigue and headaches. She appears confused and apathetic. She has been taking diuretics to treat her hypertension and paroxetine for her depression. Laboratory results are as follows: Urine flow = 1 L/day Plasma sodium = 125 mmol/L Plasma potassium = 4 mmol/L Urine osmolality = 385 mOsm/L Urine sodium = 125 mmol/L Urine potassium = 25 mmol/L Which of the following is the patient's approximate free water clearance? a. −0.20 L/day b. −0.50 L/day c. −0.75 L/day d. +0.2 L/day e. +0.50 L/day

The answer is a.

385. A 28-year-old woman with systemic lupus erythematosus is brought to the emergency department after developing hypokalemic paralysis. Arterial blood gas analysis shows a Pa O2 of 102 mm Hg and a pH of 7.1. She is diagnosed with type I renal tubular acidosis (RTA) caused by an autoimmune response that damages the H+-ATPase on the distal nephron. Which of the following laboratory measurements will most likely be normal in this patient? a. Anion gap b. Aldosterone secretion c. Net acid excretion d. Serum bicarbonate e. Urine ammonium

The answer is a.

371. A 16-year-old girl presents for her annual high school athletic physical. She states that she seems more tired than usual, she has been having muscle cramps in her calves, and her legs get very weak and sore after running and playing soccer. Her blood pressure is 160/100 mm Hg, and her ECG shows a prolonged QT interval and the presence of a U wave. Blood analysis shows hypokalemia, metabolic alkalosis, and decreases in plasma renin activity and aldosterone concentration. Her clinical condition is reversed after she is placed on the diuretic amiloride. Based on this finding, which of the following renal transport processes is the major defect causing her metabolic disorder? a. Greater than normal sodium reabsorption by the proximal tubules b. Greater than normal sodium reabsorption by the cortical collecting ducts c. Inability of the distal nephron to secrete hydrogen d. Inability of the distal nephron to secrete potassium ion e. Inability to concentrate urine

The answer is b.

382. A 68-year-old woman presents with hypertension and oliguria. A CT of the abdomen reveals a hypoplastic left kidney. Based on the following laboratory data, which of the following is her estimated RPF? Renal artery p-aminohippuric acid (PAH) = 6 mg/dL Renal vein PAH = 0.6 mg/dL Urinary PAH = 25 mg/mL Urine flow = 1.5 mL/min Hematocrit = 40% a. 475 mL/min b. 550 mL/min c. 625 mL/min d. 700 mL/min e. 775 mL/min

The answer is c.

376. A 32-year-old man complaining of fatigue and muscle weakness is seen by his physician. Blood tests reveal a serum glucose level of 325 mg/dL and serum creatinine of 0.8 mg/dL. Results of a 24-hour urine analysis are as follows: Total volume = 5L Total glucose = 375 g Total creatinine = 2.4 g The patient's GFR is approximately which of the following? a. 75 mL/min b. 100 mL/min c. 125 mL/min d. 200 mL/min e. 275 mL/min

The answer is d.

380. A 17-year-old girl went on a starvation diet for 3 days before prom so that she would look thin in her new dress. Her mother found her lethargic and hyperventilating, and took her to the emergency department for evaluation. Based on the following laboratory values, which of the following is her net acid excretion? Plasma pH = 7.26 Urine flow = 1.2 L/day Urine bicarbonate = 2 mEq/L Urine titratable acids = 24 mEq/L Urine ammonium = 38 mEq/L Urine pH = 5.4 a. 60 mEq/L b. 64 mEq/L c. 68 mEq/L d. 72 mEq/L e. 76 mEq/L

The answer is d.

408. A 38-year-old woman is admitted to the hospital by her physician because of decreased urine output. Prior to admission, she was rehearsing for a dance performance and had been taking ibuprofen (Motrin) for pain. Laboratory data reveal the following: BUN, 49 mg/dL; serum sodium, 135 mmol/L; serum creatinine, 7.5 mg/dL; urine sodium, 33 mmol/L, and urine creatinine, 90 mg/dL. Her fractional sodium excretion is approximately which of the following? a. 0.5% b. 1.0% c. 1.5% d. 2.0% e. 3.0%

The answer is d.

372. A previously well 12-year-old boy is brought to the emergency department with vomiting and severe abdominal cramps after a prolonged period of exercise. Elevated levels of serum creatinine and blood urea nitrogen (BUN) suggest acute renal failure. Following treatment and recovery, his serum uric acid concentration (0.6 mg/dL) remains consistently below normal. To determine if his low serum uric acid level is related to renal dysfunction, uric acid clearance studies are conducted and the following data are obtained: Urine flow rate = 1 mL/min Urine [uric acid] = 36 mg/dL Which of the following is the patient's uric acid clearance? a. 6 mL/min b. 12 mL/min c. 24 mL/min d. 48 mL/min e. 60 mL/min

The answer is e.

22yo female presents with altered mental status. You run a CMP and notice hyponatremia with a low BUN. Her fiend who brought her in said she suffered a head injuy due to crashing her bike this moning. What is the most likely diagnosis? A Central diabetes insipidus B Nephrogenic diabetes insipidus C SIADH D Psychogenic polydipsia

the answer here is syndrome of inappropiate ADH SIADH. SIADH in the setting of HEAD TRAUMA (can also be due to stroke, CNS tumor, Small cell lung Cancer).Too much ADH is being excreted, causing increased free water retention and impaired water excretion -→ hyponatremia/kidney unable to dilute uine. Confusion came from symptomatic hyponatremia (neurologic sxs d/t cerebral edema - edema is d/t relative hypotonicity of ECF shifting water into cells). Diabetes insipidus is also caused by head trauma. However, you would get decreased oral free water intake → hypenatremia. Kidneys cannot concentrate uine -→ produces large amounts of DILUTE uine.