a. 100 mg/min

b. 200 mg/min

c. 300 mg/min

d. 400 mg/min

e. 500 mg/min

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

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

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

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

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

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

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.

378. A 60-year-old woman presents to her gynecologist with progressive fatigue, weakness, and diffuse bony pain. She has been postmenopausal for 5 years, and her medical history is notable for hypertension and recurrent kidney stones. Physical examination is insignificant except for a slight dorsal kyphosis. A bone scan confirms osteoporosis. Serum calcium and parathyroid hormone (PTH) are increased and serum phosphate is decreased. PTH increases Ca²⁺ reabsorption at which of the points along the nephron pictured below?

a. A

b. B

c. C

d. D

e. E

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

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

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

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

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

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

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

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

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

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.

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

390. A 10-year-old boy is brought to the emergency department with a brief history of severe, excruciating left flank pain, nausea, vomiting, and hematuria. The patient has had one similar episode in the past that brought him to the emergency department a few months ago. The boy also has a family history of recurrent kidney stones. Urinalysis showed hematuria and microscopic evaluation of the urinary sediment showed hexagonal crystals. An abdominal radiograph of the patient demonstrated the appearance of a faintly, opaque, ground glass stone in the left ureter. The patient’s reoccurring clinical presentation is likely due to a defect in amino acid reabsorption in the kidney. What part of the kidney is responsible for the majority of amino acid reabsorption?

a. A

b. B

c. C

d. D

e. E

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.

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.

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

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.

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

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.

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.

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

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

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

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

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.

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).

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

405. A 27-year-old man with bipolar disorder presents to his psychiatrist complaining that since he started his lithium treatment 6 months ago, he is frequently thirsty and gets up three or four times each night to urinate. Head–neck examination reveals slightly dry mucous membranes. Urinalysis reveals polyuria with a dilute urine. Serum ADH is normal. A diagnosis of lithium-induced nephrogenic diabetes insipidus is suspected. In the absence of ADH or when the kidney lacks responsiveness to ADH, the luminal Na⁺ concentration will be lowest at which of the points along the nephron shown schematically in the diagram below?

a. A

b. B

c. C

d. D

e. 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

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

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%

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.

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

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

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

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

c. H⁺ secretion by the distal nephron

d. Production of ammonia by the proximal tubule

e. Production of new bicarbonate by the distal nephron

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

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

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

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

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

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

For Questions 420 and 421, refer to the following case.

A 39-year-old woman with chronic kidney disease secondary to a longstanding history of type I diabetes mellitus and hypertension presents to the nephrologist for follow-up of her hypertension. The patient was recently started on amiloride. Her review of systems is positive for muscle weakness and some chest pain during the last 2 weeks. Her blood pressure is 155/92 mm Hg and an ECG reveals tall, peaked T waves. Blood results show a pH of 7.25, Na⁺ 140, Cl⁻ 120, 18, K⁺ 6.0, and decreased aldosterone and plasma renin activity. Urinary ammonium (NH₄⁺) excretion is decreased.

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.

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⁺

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

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

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

425. A 42-year-old man presents with fatigue, loss of stamina, and frequent urination. He is not taking any medications currently. Physical examination is normal except for a blood pressure of 165/95 mm Hg. Serum electrolytes show sodium, 152 mEq/L; potassium, 3.1 mEq/L; chloride, 112 mEq/L; and bicarbonate, 32 mEq/L. Aldosterone concentration is elevated and plasma renin activity is low, consistent with primary hyperaldosteronism. Aldosterone increases Na⁺ reabsorption at which of the point depicted in this schematic diagram of the nephron?

a. A

b. B

c. C

d. D

e. E

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

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

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

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

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

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

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

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

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

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