Chapter 35 and 36
Creatinine is constantly released from _____ tissue and excreted primarily by glomerular filtration.
muscle
The kidney disorder characterized by hypoalbuminemia, edema, hyperlipidemia and lipiduria is:
nephrotic syndrome
How can a person with chronic renal failure become anemic? How are they related?
normochromic (normal hemoglobin that gives the red color of the blood) anemia is a companion to chronic renal failure because of the insufficient production and release of erythropoietin, blood loss, and decreased red blood cell life span.
Five major functions of the PCT (proximal convoluted tubule)
-Reabsorption of Organic Nutrients: PCT reabsorbs > 99 % of glucose, amino acids, and other nutrients. -Active Reabsorption of Ions: PCT actively transport ions; Na, K, Mg, HCO3, Phosphate, and sulfate ions. Bicarbonate is important in stabilizing blood pH. -Reabsorption of Water. -Passive Reabsorption of Ions: Urea, chloride ions, and lipid-soluble materials may diffuse out of the PCT by passive diffusion. -Secretion: Active secretion also occurs along the PCT. The DCT performs comparatively little reabsorption than PCT.
Benefits of Countercurrent Multiplication
1. It efficiently reabsorbs solutes and water before the tubular fluid reaches the DCT and collecting system. 2. It establishes a concentration gradient that permits the passive reabsorption of water from the tubular fluid in the collecting system. This reabsorption is regulated by circulating levels of antidiuretic hormone (ADH).
Nephrons
2 types: ones in the cortex, ones in the medulla 1. The glomerulus: the blood kidney interface, plasma is filtered from capillaries into the Bowman's capsule. 2. Proximal convoluted tubule: reabsorbs most of the filtered load, including nutrients and electrolytes. 3. Loop of Henle: concentrates urine by increasing the osmolality of surrounding tissue and filtrate. 4. Distal convoluted tubule: reabsorbs Na and H2O 5. Collecting system: collects urine for excretion.
What is a urethral stricture and what causes it?
A urethral stricture occurs when the lumen is narrowed as a result of infection, trauma, or surgical manipulation, which leaves a scar and then reduces the size of the urethra.
Pyelonephritis
Acute infection of the ureter, renal pelvis, and/or renal parenchyma Contributing factors: Cystitis, Urinary tract obstruction with reflux infection Clinical manifestations: flank pain, fever, chills, costobertebral tenderness, puss in urine
Match the causes of acute renal failure with examples of specific disorders
Acute tubular necrosis: Intrarenal Hypovolemia: Prerenal Prostatic Hypertrophy: Postrenal
How the Countercurrent multiplication operates
A. Na & Cl are pumped out of the thick ascending limb and into the peritubular fluid. B. The result is an osmotic flow of water out of the thin descending limb & into the peritubular fluid, increasing the solute concentration in the thin descending limb. C. The arrival of the highly concentrated solution in the thick ascending limb accelerates the transport of Na & Cl into the peritubular fluid of the medulla. D. This arrangement is a simple positive feedback loop: Solute pumping at the ascending limb leads to higher solute concentrations in the descending limb, which then result in accelerated solute pumping in the ascending limb.
Renal Failure
Acute: Sudden and rapidly progressive within hours (often reversible); abrupt reduction in renal function Chronic: slowly progressing to end-stage renal failure over months or years Azotemia: increased urea and frequently creatinine levels Uremia: elevated urea and creatinine levels with fatigue, anorexia, nausea, vomiting, diarrhea, weight loss, pruritus, edema, neurologic changes (all related to retention of toxic wastes, deficiency states, and electrolyte disorders)
Urinary Tract Obstruction
Blockage of urine flow within the urinary tract due to an obstruction that can be caused by an anatomic or functional defect Hydroureter: distention of the ureter with urine or watery fluid, due to obstruction. Hydronephrosis : distention of the renal calyces and pelvis with urine as a result of obstruction of the outflow of urine distal to the renal pelvis.
Prerenal Acute Renal Failure (ARF)
Caused by impaired renal blood flow (sudden reduction of perfusion to the kidneys) GFR declines due to the decrease in filtration pressure (results in oliguria) Ischemia leads to hypoxic injury and acute tubular necrosis (ATN)
Concentration and Dilution of Urine
Countercurrent exchange system -Contributes to production of concentrated urine -Fluid flows in opposite direction through parallel tubes -Fluid moves up and down the parallel limbs of the loop of Henle -The longer the loop, the greater the concentration gradient
Intrarenal ARF
Damage to the renal parenchyma: acute tubular necrosis (most common cause)
Aging and Renal Function
Decrease in kidney size Decrease in renal blood flow and GFR Number of nephrons decrease due to renal vascular and perfusion changes Glomerular capillaries atrophy Tubular transport response decreases Increased bladder symptoms Urgency, frequency, and nocturia
Diuresis
Diuresis is the elimination of urine. Diuretics are drugs that promote the loss of water in urine. The usual goal in diuretic therapy is a reduction in blood volume, blood pressure, extracellular fluid volume, or all three.
Which abnormal lab value is found in glomerular disorders?
Elevated creatinine clearance
The most common causes of uncomplicated urinary tract infections are:
Escherichia coli
Nephrotic Syndrome
Excretion of 3.5 g or more of protein in the urine per day. Protein excretion is due to glomerular injury Findings: Hypoalbuminemia, edema, hyperlipidemia, and lipiduria
Urolithiasis: Kidney Stones
Factors affecting stone formation: Crystal growth-inhibiting substances and particle retention. Stones: Most common; Ca oxalate or Ca phosphate.
Which clinical manifestation of pyelonephritis is different from those of cystitis?
Flank pain
Glomerular Disorders
Glomerular disease has sudden or insidious onset of hypertension, edema, and an elevated blood urea nitrogen (BUN) Characterized by: Decreased glomerular filtration rate, increased glomerulur capillary permeability, elevated plasma creatinine, urea, and reduced creatinine clearance The increased glomerulur capillary permeability causes loss of negative ionic charge barrier result in passage of plasma proteins (i.e. albumin) into the urine. Resulting hypoalbuminemia encourages plasma fluid to move into the interstitial spaces. Result of glomerular damage: decreased glomerular membrane surface area, glomerular capillary blood flow, blood hydrostatic pressure
Nephron Function
Glomerular filtration Net filtration pressure (NFP): increases when the glomerular membrane is inflamed due to increase presence of proteins in the glomerular filtrate. Glomerular hydrostatic pressure: A narrowed proximal convoluted tubule results in increased capsular hydrostatic pressure. Filtration rate (GFR): As blood volume decreases, GFR and NFP decrease. The decreased blood volume ultimately decreases the blood pressure. GFR is a test used to check how well the kidneys are working. Specifically, it estimates how much blood passes through the tiny filters in the kidneys, called glomeruli, each minute.
A patient has hematuria with casts and proteinuria exceeding 3 to 5 g/day with albumin as the major protein. This data suggest the presence of which disorder?
Glomerulonephritis
Causes of Nephrotic Syndrome
Glomerulonephritis, Genetic defects that alter the glomerular membrane, Systemic diseases (diabetes, SLE), Drug/toxin injury, Infections (especially chronic and/or recurrent)
Considering host defense mechanisms, which element in the urine is bacteriostatic (prevents the growth of bacteria), if any?
High urea
The Effects of ADH on the DCT and Collecting Duct
In the absence of ADH, water is not reabsorbed in these segments, so all the fluid reaching the DCT is lost in the urine. As ADH levels rise, the DCT and collecting system become more permeable to water, the amount of water reabsorbed increases, and the urine osmotic concentration climbs.
Glomerulonephritis
Inflammation of the glomerulus Most commonly cause by immunologic abnormalities. Decreased glomerular perfusion (glomerular blood flow) due to inflammation, Glomerular sclerosis (scarring), and Thickening of the glomerular basement membrane (but increased permeability to proteins).
Urinary Tract Infection (UTI)
Inflammation of the urinary epithelium following invasion and colonization by some pathogen within the urinary tract Cystitis: An inflammation of the bladder Most common pathogens: Escherichia coli, Staphylococcus saprophyticus
What causes renal stones to form?
Kidney stones consist of large amounts of crystal, protein, or other kinds of substances.
The most common type of renal stone is comprised of:
calcium oxalate
Kidney Stone Diagnosis and Prognosis
Manifestation: Renal colic Evaluation: Stone analysis, Kidney-ureter-bladder (KUB), Intravenous pyelogram, and Spiral abdominal computed tomography (CT) Treatment: Stone removal
Kidney Stones: Calculi
Masses of crystals, protein, or other substances that form within and may obstruct urinary tract. Risk factors: Male, Age 20-40 years, Inadequate fluid intake (biggest contributor), Living in desert or tropical region (temperature, humidity, fluid, and dietary patterns).
Ms. Cornwall is admitted with pyelonephritis. She has chills and her temperature is 101° F. She is complaining of flank pain, frequency, and dysuria. Her urine has white blood cell casts, and her urine culture is growing Escherichia coli. Why does she have bacteria and white blood cell casts in her urine?
Ms. Cornwall has a focal bacterial infection of her renal pelvis, calyces, and medulla. The bacterial invasion triggers an inflammatory reaction with white blood cell response causing edema and release of inflammatory mediators.
Which antibiotics are considered "major culprits" in causing nephrotoxic acute tubular necrosis (ATN)?
Neomycin, gentamicin, and tobramycin
Multiorgan/Multisystem Failures
Neurologic: Neuropathies, Encephalopathy Gastrointestinal: Nausea, vomiting, anorexia Endocrine: Insulin resistance, Decreased sex hormones Metabolic: Altered protein, lipid, carbohydrate metabolism Integumentary, bone, mineral: Hyperphosphatemia, Hypocalcemia, Hyperparathyroidism (brittle bones), Skin changes (bruises, itching, uremic frost, yellowing) Immune dysfunction: Immunosuppression
Postrenal ARF
Occurs with urinary tract obstructions that affect the kidneys bilaterally and increase the intraluminal pressure upstream (decrease in GFR) -Prostatic hypertrophy, Bladder outlet obstruction, Bilateral ureteral obstruction
Clinical Manifestations of ARF
Oliguria/anuria Elevated BUN and creatinine Hyperkalemia Metabolic acidosis Hypertension (volume overload)
What is the difference among prerenal acute renal failure, intrarenal acute renal failure, and postrenal acute renal failure? Give examples of each.
Prerenal acute renal failure is decreased renal function with elevated blood urea nitrogen (BUN) and plasma creatinine caused by impaired blood flow to the kidney. Intrarenal acute renal failure is caused by impaired blood flow within the kidney. It is the result of direct damage to the kidney including ischemia or inflammatory damage. Postrenal acute renal failure is caused by impaired outflow from the kidney. The passage of urine is blocked by an obstruction, causing urine to "back up" into the renal pelvis and altering pressures within the kidney.
Hormonal regulation of RBF/GFR
The major mechanism for hormonal regulation is the renin-angiotensin-aldosterone system, which can increase systemic arterial pressure and change renal blood flow. Release of renin can be inhibited by atrial natriuretic peptide, resulting in decreased blood pressure.
What causes acute cystitis (infection of the urinary bladder)?
The most common microorganisms are strains of Escherichia coli and Staphylococcus saprophyticus.
Preinuria and Hematuria
Proteinuria (protein loss in urine) commonly occurs after long-distance events because the glomerular cells have been injured by prolonged hypoxia (low oxygen levels). If the damage is substantial, hematuria (blood loss in urine) will occur. Painless hematuria may be sign of bladder cancer.
Structures of the Kidney
Renal cortex: (external) receives most of the blood flow, and is mostly concerned with reabsorbing filtered material. Renal medulla: (internal) is a highly metabolically active area, which serves to concentrate the urine. Renal pelvis: collects urine for excretion. Afferent arterioles: bring blood to Glomerulus Efferent arterioles: bring blood away from Glomerulus
Renal Dysfunction
Renal insufficiency, Renal failure, End-stage renal failure (ESRD - need transplant), Uremia, Azotemia
Water and Solute regulation
The normal amount of water and solute loss in the collecting system is regulated in two ways: 1. By aldosterone, which controls sodium ion pumps along most of the DCT and the proximal portion of the collecting system. 2. By ADH, which controls the permeability of the DCT and collecting system to water.
Reabsorption
Sodium Ion Reabsorption: The collecting system contains aldosterone-sensitive ion pumps that exchange in tubular fluid for in peritubular fluid. Bicarbonate Reabsorption: Bicarbonate ions are reabsorbed in exchange for chloride ions in the peritubular fluid. Urea Reabsorption: The concentration of urea in the tubular fluid entering the collecting duct is relatively high.
Neurol regulation of RBF/GFR
Sympathetic nervous system: It produces a powerful vasoconstriction of the afferent arterioles, decreasing the GFR and slowing the production of filtrate (b1 stimulation). Vasoconstriction (diminishes GFR) Autonomic Regulation of the GFR Most of the autonomic innervation of the kidneys consists of sympathetic postganglionic fibers. (The role of the few parasympathetic fibers in regulating kidney function is not known.)
Renal "Clearance"
The ability of the kidneys to filter a substance and excrete it in the urine is a reflection of the GFR, tubular secretion, and tubular reabsorption (thus also RBF and functioning of nephrons)
Secretion
The collecting system is an important site for the control of body fluid pH by means of the secretion of hydrogen or bicarbonate ions.
What are the goals in treating renal calculi?
The goals for treating kidney stones are acute pain management, stone passage promotion, stone size reduction, and prevention of new stone formation.
Chronic Renal Failure
The irreversible loss of renal function that affects nearly all organ systems Progression: Reduced renal reserve, Renal insufficiency, Renal failure, End-stage renal disease
Functions of the kidney
The kidney regulates fluid and electrolyte balance by filtration, excretion and reabsorption. It activates both erythropoeitin (for production of red blood cells) & vitamin-D which regulates calcium metabolism. It also produces renin (in the afferent arteriole) which affects various aspects of water and electrolyte homeostasis.
How does acute unilateral renal obstruction predispose people to hypertension?
The reduced perfusion of the affected kidney activates the renin-angiotensin-aldosterone system, which causes constriction of peripheral arterioles.
Which statements are true about struvite stones?
They grow large and branch into a staghorn configuration in renal pelvis and calyces, they are more common in women than men, and they are closely associated with urinary tract infections caused by urease-producing bacteria, such as Pseudomonas.
Concentration and Dilution of Urine
Urea Catecholamines Antidiuretic hormone (ADH) Natriuretic peptide Diuretics
Control of Urine Volume & Osmotic Concentration
Urine volume and osmotic concentration are regulated by controlling the reabsorption of water. Water is reabsorbed by osmosis in the PCT and the loop of Henle. The ascending limb of the loop of Henle is impermeable to water, but 1-2 % of the volume of water in the original filtrate is recovered during sodium ion reabsorption in the DCT and collecting system.
How are glucose and insulin used to treat hyperkalemia associated with acute renal failure?
When insulin transports glucose into the cell, it also carries potassium with it.
Physicians frequently request a clean-catch midstream urine sample. Why?
a physician is trying to get the best representative sample of a person's urine.
Pyelonephritis is usually caused by antibody-coated:
bacteria
Clinical manifestations of a urinary tract infection in an 85 year old may include:
confusion and poorly localized abdominal discomfort
Anemia of chronic renal failure can be successfully treated with:
erythropoietin
Hypercalciuria is usually attributable to:
hyperthyroidism, intestinal hyperabsorption of dietary calcium, and bone demineralization caused by prolonged immobilization.
Autoregulation of RBF/GFR
through baroreceptors (measuring renal bp through the glomerulus) and NaCl levels monitored by the macula densa. Neural regulation
