Pathophysiology Quiz: Acute Kidney Injury Aki
20 questions · exam conditions
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Acute Kidney Injury AkiQuestion 1 of 20

A patient with congestive heart failure relies on renal prostaglandin synthesis to maintain renal blood flow. The addition of which medication would most likely precipitate a prerenal AKI by interfering with this compensatory mechanism?

Spironolactone
Lisinopril
Naproxen
Amlodipine
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Pathophysiology Quiz

Pathophysiology Quiz: Acute Kidney Injury Aki

Practice Acute Kidney Injury Aki in Pathophysiology with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Acute Kidney Injury Aki, giving you a quick way to practice the rules, question types, and explanations that matter most for Pathophysiology.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

A patient with congestive heart failure relies on renal prostaglandin synthesis to maintain renal blood flow. The addition of which medication would most likely precipitate a prerenal AKI by interfering with this compensatory mechanism?

  1. Spironolactone
  2. Lisinopril
  3. Naproxen (correct answer)
  4. Amlodipine
Explanation: In states of low effective circulating volume like heart failure, the kidneys produce prostaglandins (PGE2, PGI2) to vasodilate the afferent arteriole and preserve renal blood flow and GFR. Naproxen, a non-steroidal anti-inflammatory drug (NSAID), inhibits cyclooxygenase (COX) enzymes, thereby blocking prostaglandin synthesis. This leads to unopposed afferent arteriolar vasoconstriction, a sharp decrease in renal blood flow, and a prerenal AKI.

Question 2

A 52-year-old woman with a history of metastatic cervical cancer treated with pelvic radiation presents with progressive fatigue and nausea. Her creatinine is 5.1 mg/dL. A renal ultrasound demonstrates bilateral hydronephrosis and hydroureter down to the level of the pelvic brim.

This patient's acute kidney injury is best categorized by which underlying mechanism?

  1. Prerenal, due to chemotherapy-induced vomiting and dehydration.
  2. Intrarenal, due to radiation nephritis causing parenchymal damage.
  3. Intrarenal, due to paraneoplastic glomerulonephritis.
  4. Postrenal, due to extrinsic compression of the ureters. (correct answer)
Explanation: The key finding is bilateral hydronephrosis and hydroureter on ultrasound, which is diagnostic of urinary outflow obstruction. Given her history of metastatic cervical cancer and pelvic radiation, the most likely cause is extrinsic compression of both ureters by a tumor mass or radiation-induced fibrosis. Obstruction of urine flow from both kidneys leads to an increase in intratubular pressure, opposing glomerular filtration and causing a postrenal AKI.

Question 3

A patient with a history of hypertension well-controlled on amlodipine presents with new-onset AKI after starting a new medication for arthritis pain two weeks ago. His blood pressure is 160/95 mmHg, and urinalysis shows sterile pyuria and white blood cell casts.

The mechanism of AKI in this patient is most likely an intrarenal process caused by:

  1. The hemodynamic effect of an NSAID on the afferent arteriole.
  2. A prerenal state induced by the calcium channel blocker amlodipine.
  3. Ischemic ATN due to uncontrolled malignant hypertension.
  4. An allergic interstitial nephritis triggered by a new medication. (correct answer)
Explanation: When you encounter AKI questions, always analyze the clinical clues systematically: timeline, associated symptoms, and urinalysis findings. The combination of new medication exposure, sterile pyuria, and white blood cell casts strongly points toward acute interstitial nephritis (AIN). The correct answer is D because this patient shows the classic triad of AIN: recent drug exposure (arthritis medication started two weeks ago), AKI, and inflammatory urinalysis findings. White blood cell casts are pathognomonic for interstitial inflammation, and sterile pyuria (white cells without bacteria) indicates non-infectious inflammation. AIN is an intrarenal process where immune-mediated inflammation damages the tubulointerstitium, commonly triggered by NSAIDs, antibiotics, or proton pump inhibitors. Option A describes NSAID-induced prerenal azotemia through afferent arteriole vasoconstriction, but this wouldn't cause white cell casts or sterile pyuria. Option B is incorrect because amlodipine doesn't typically cause prerenal states—calcium channel blockers are vasodilatory and nephroprotective. Option C suggests ischemic ATN from malignant hypertension, but his blood pressure (160/95) isn't severely elevated enough, and ATN typically shows muddy brown casts, not white cell casts. Remember this pattern: when you see AKI plus sterile pyuria plus white cell casts plus recent medication exposure, think allergic interstitial nephritis first. The urinalysis findings are your biggest clue—they differentiate AIN from other causes of drug-induced kidney injury like prerenal azotemia or ATN.

Question 4

A 30-year-old male is rescued from a collapsed building and presents with severe crush injuries to his lower extremities. His urine is dark brown and his serum creatine kinase is markedly elevated. He develops oliguric acute kidney injury.

The intrarenal component of this patient's AKI is primarily caused by which combination of events?

  1. Glomerular injury from circulating inflammatory cytokines and prerenal azotemia.
  2. Intratubular obstruction by myoglobin casts and heme-protein induced oxidative injury. (correct answer)
  3. Acute interstitial nephritis triggered by muscle antigens and renal hypoperfusion.
  4. Postrenal obstruction from blood clots and debris in the ureters.
Explanation: In rhabdomyolysis, massive muscle breakdown releases myoglobin into the circulation. The filtered myoglobin causes intrarenal AKI through two main mechanisms. First, myoglobin precipitates with Tamm-Horsfall protein in the distal tubules, especially in acidic urine, forming casts that cause physical obstruction. Second, the heme iron within myoglobin catalyzes the formation of reactive oxygen species, leading to direct oxidative damage and toxicity to the tubular epithelial cells.

Question 5

A patient in the ICU for septic shock has persistent hypotension with a mean arterial pressure of 60 mmHg. On admission, his creatinine was 1.0 mg/dL and a calculated FENa was 0.4%. After 48 hours of vasopressor support, his creatinine is 3.2 mg/dL, he is oliguric, and a repeat FENa is 3.1%.

What is the most likely pathophysiological transition that has occurred in the kidneys?

  1. From postrenal obstruction to a persistent prerenal state.
  2. From a functional prerenal state to established ischemic acute tubular necrosis. (correct answer)
  3. From acute interstitial nephritis to rapidly progressive glomerulonephritis.
  4. From ischemic acute tubular necrosis to a volume-responsive prerenal state.
Explanation: The initial presentation with hypotension and a low FENa (<1%) is characteristic of prerenal azotemia, where renal perfusion is low but tubular function is intact. The persistent ischemia from prolonged shock has caused structural damage to the renal tubules, leading to the development of acute tubular necrosis (ATN). This transition is marked by the loss of tubular reabsorptive capacity, causing the FENa to rise above 2%, and a failure of renal function to improve despite hemodynamic support.

Question 6

A patient is admitted with AKI. The following laboratory values are obtained: Serum Cr 4.0 mg/dL, Serum BUN 52 mg/dL, Serum Na+ 140 mEq/L, Urine Na+ 60 mEq/L, and Urine Cr 40 mg/dL.

Based on a calculation of the fractional excretion of sodium (FENa), which type of AKI is most likely present?

  1. Prerenal AKI, with a calculated FENa of approximately 0.5%.
  2. Postrenal AKI, as the FENa cannot distinguish the underlying cause.
  3. Intrarenal AKI, with a calculated FENa of approximately 4.3%. (correct answer)
  4. Prerenal AKI, with a BUN/creatinine ratio greater than 20:1.
Explanation: The FENa is calculated as: [(Urine Na / Serum Na) / (Urine Cr / Serum Cr)] x 100. Plugging in the values: FENa = [(60 / 140) / (40 / 4.0)] x 100 = [(0.428) / (10)] x 100 = 0.0428 x 100 = 4.28% (or ~4.3%). A FENa > 2% is highly suggestive of an intrinsic renal process, specifically acute tubular necrosis (ATN), where damaged tubules are unable to reabsorb sodium effectively. The BUN/Cr ratio of 13 (52/4) also supports an intrarenal process over a prerenal one.

Question 7

A 75-year-old male with a history of benign prostatic hyperplasia (BPH) presents to the emergency department with anuria for the past 24 hours and lower abdominal discomfort. His serum creatinine is 7.2 mg/dL and BUN is 90 mg/dL. An indwelling urinary catheter is placed, yielding 2 liters of urine immediately. Over the next 24 hours, his urine output totals 6 liters.

Which set of pathophysiological changes and corresponding laboratory findings is most expected during this period of post-obstructive diuresis?

  1. Impaired tubular response to ADH, leading to low urine sodium and hyperkalemia.
  2. Ischemic tubular injury, resulting in muddy brown casts and a rising creatinine.
  3. Accumulated osmotic solutes, causing high urine sodium, polyuria, and potential hypokalemia. (correct answer)
  4. Glomerular hyperfiltration, leading to low urine osmolality and hypernatremia.
Explanation: Relief of a prolonged urinary obstruction leads to post-obstructive diuresis. This is driven by the excretion of accumulated solutes (like urea) that act as an osmotic diuretic, as well as impaired tubular function causing sodium and water wasting. This results in a high volume of urine with a high sodium concentration. The high flow rate through the distal nephron can also lead to significant potassium wasting and hypokalemia.

Question 8

A 62-year-old male with a history of atherosclerotic disease is found to have bilateral renal artery stenosis. He is started on lisinopril for management of his hypertension. One week later, his serum creatinine has increased from 1.3 mg/dL to 2.6 mg/dL.

This acute decline in renal function is primarily due to the drug's effect on which of the following?

  1. Vasodilation of the efferent arteriole, reducing glomerular filtration pressure. (correct answer)
  2. Vasoconstriction of the afferent arteriole, reducing renal blood flow.
  3. Induction of an allergic interstitial nephritis, causing inflammation.
  4. Direct cytotoxic effect on the proximal tubular epithelial cells.
Explanation: In patients with bilateral renal artery stenosis, the glomerular filtration rate (GFR) is highly dependent on angiotensin II-mediated constriction of the efferent arteriole to maintain adequate pressure within the glomerulus. Lisinopril, an ACE inhibitor, blocks the production of angiotensin II. This leads to efferent arteriolar vasodilation, which causes a sharp drop in intraglomerular hydrostatic pressure and, consequently, a significant decrease in GFR.

Question 9

A patient is admitted with oliguric AKI. To differentiate prerenal azotemia from established acute tubular necrosis (ATN), a 1-liter bolus of intravenous normal saline is administered. The patient's urine output remains less than 20 mL/hour.

Which additional finding after the fluid challenge would most strongly support the diagnosis of ATN over a prerenal state?

  1. A rapid increase in urine output to over 100 mL/hour.
  2. A decrease in the BUN/creatinine ratio from 25:1 to 18:1.
  3. A fractional excretion of sodium (FENa) that remains elevated at 2.8%. (correct answer)
  4. A rise in urine osmolality from 450 mOsm/kg to 600 mOsm/kg.
Explanation: In prerenal AKI, restoring volume with a fluid challenge should improve renal perfusion, leading to an increase in urine output and a decrease in sodium reabsorption. In established ATN, the tubular cells are damaged and cannot respond to the improved perfusion. They are unable to reabsorb sodium effectively, regardless of volume status. Therefore, the persistence of oliguria and a high FENa (>2%) after adequate volume resuscitation is a key feature that distinguishes ATN from a prerenal state.

Question 10

A 45-year-old female is being treated with gentamicin for gram-negative sepsis. Her baseline creatinine was 0.8 mg/dL. On day 7 of therapy, her creatinine has risen to 2.1 mg/dL. A urinalysis is performed.

Which finding in the urine sediment would most specifically suggest an intrarenal mechanism of AKI related to this medication?

  1. Numerous red blood cell casts, indicating glomerular inflammation.
  2. Large numbers of white blood cells and prominent eosinophiluria.
  3. Abundant granular, pigmented 'muddy brown' casts. (correct answer)
  4. Hyaline casts and a BUN to creatinine ratio greater than 20:1.
Explanation: Gentamicin, an aminoglycoside, is a classic nephrotoxin that causes intrarenal AKI via direct toxicity to the proximal tubular cells. This leads to acute tubular necrosis (ATN). The sloughing of these necrotic epithelial cells into the tubular lumen forms characteristic granular, pigmented casts often described as 'muddy brown'. This finding is pathognomonic for ATN.

Question 11

A 28-year-old woman develops a morbilliform rash, a fever of 38.5°C, and joint pains ten days after starting a course of penicillin for a throat infection. Laboratory work reveals a serum creatinine of 3.1 mg/dL (baseline 0.8 mg/dL) and peripheral eosinophilia. Her urinalysis shows white blood cell casts.

Given this clinical presentation, the patient's acute kidney injury is best classified as which type?

  1. Prerenal azotemia due to septic physiology from the initial infection.
  2. Intrarenal AKI due to drug-induced acute interstitial nephritis. (correct answer)
  3. Intrarenal AKI due to post-infectious glomerulonephritis.
  4. Postrenal AKI due to sulfonamide crystal-induced obstruction.
Explanation: The patient's presentation with the classic triad of fever, rash, and arthralgia, combined with the timing after drug initiation, peripheral eosinophilia, and urinalysis showing white blood cell casts (and likely eosinophiluria), is pathognomonic for acute interstitial nephritis (AIN). AIN is a type of intrarenal AKI caused by an allergic, inflammatory infiltrate in the renal interstitium, most commonly triggered by medications like penicillins.

Question 12

A patient in the ICU for septic shock has persistent hypotension with a mean arterial pressure of 60 mmHg. On admission, his creatinine was 1.0 mg/dL and a calculated FENa was 0.4%. After 48 hours of vasopressor support, his creatinine is 3.2 mg/dL, he is oliguric, and a repeat FENa is 3.1%.

What is the most likely pathophysiological transition that has occurred in the kidneys?

  1. From postrenal obstruction to a persistent prerenal state.
  2. From a functional prerenal state to established ischemic acute tubular necrosis. (correct answer)
  3. From acute interstitial nephritis to rapidly progressive glomerulonephritis.
  4. From ischemic acute tubular necrosis to a volume-responsive prerenal state.
Explanation: The initial presentation with hypotension and a low FENa (<1%) is characteristic of prerenal azotemia, where renal perfusion is low but tubular function is intact. The persistent ischemia from prolonged shock has caused structural damage to the renal tubules, leading to the development of acute tubular necrosis (ATN). This transition is marked by the loss of tubular reabsorptive capacity, causing the FENa to rise above 2%, and a failure of renal function to improve despite hemodynamic support.

Question 13

A 75-year-old male with a history of benign prostatic hyperplasia (BPH) presents to the emergency department with anuria for the past 24 hours and lower abdominal discomfort. His serum creatinine is 7.2 mg/dL and BUN is 90 mg/dL. An indwelling urinary catheter is placed, yielding 2 liters of urine immediately. Over the next 24 hours, his urine output totals 6 liters.

Which set of pathophysiological changes and corresponding laboratory findings is most expected during this period of post-obstructive diuresis?

  1. Impaired tubular response to ADH, leading to low urine sodium and hyperkalemia.
  2. Ischemic tubular injury, resulting in muddy brown casts and a rising creatinine.
  3. Accumulated osmotic solutes, causing high urine sodium, polyuria, and potential hypokalemia. (correct answer)
  4. Glomerular hyperfiltration, leading to low urine osmolality and hypernatremia.
Explanation: Relief of a prolonged urinary obstruction leads to post-obstructive diuresis. This is driven by the excretion of accumulated solutes (like urea) that act as an osmotic diuretic, as well as impaired tubular function causing sodium and water wasting. This results in a high volume of urine with a high sodium concentration. The high flow rate through the distal nephron can also lead to significant potassium wasting and hypokalemia.

Question 14

A 45-year-old female is being treated with gentamicin for gram-negative sepsis. Her baseline creatinine was 0.8 mg/dL. On day 7 of therapy, her creatinine has risen to 2.1 mg/dL. A urinalysis is performed.

Which finding in the urine sediment would most specifically suggest an intrarenal mechanism of AKI related to this medication?

  1. Numerous red blood cell casts, indicating glomerular inflammation.
  2. Large numbers of white blood cells and prominent eosinophiluria.
  3. Abundant granular, pigmented 'muddy brown' casts. (correct answer)
  4. Hyaline casts and a BUN to creatinine ratio greater than 20:1.
Explanation: Gentamicin, an aminoglycoside, is a classic nephrotoxin that causes intrarenal AKI via direct toxicity to the proximal tubular cells. This leads to acute tubular necrosis (ATN). The sloughing of these necrotic epithelial cells into the tubular lumen forms characteristic granular, pigmented casts often described as 'muddy brown'. This finding is pathognomonic for ATN.

Question 15

A 62-year-old male with a history of atherosclerotic disease is found to have bilateral renal artery stenosis. He is started on lisinopril for management of his hypertension. One week later, his serum creatinine has increased from 1.3 mg/dL to 2.6 mg/dL.

This acute decline in renal function is primarily due to the drug's effect on which of the following?

  1. Vasodilation of the efferent arteriole, reducing glomerular filtration pressure. (correct answer)
  2. Vasoconstriction of the afferent arteriole, reducing renal blood flow.
  3. Induction of an allergic interstitial nephritis, causing inflammation.
  4. Direct cytotoxic effect on the proximal tubular epithelial cells.
Explanation: In patients with bilateral renal artery stenosis, the glomerular filtration rate (GFR) is highly dependent on angiotensin II-mediated constriction of the efferent arteriole to maintain adequate pressure within the glomerulus. Lisinopril, an ACE inhibitor, blocks the production of angiotensin II. This leads to efferent arteriolar vasodilation, which causes a sharp drop in intraglomerular hydrostatic pressure and, consequently, a significant decrease in GFR.

Question 16

A 67-year-old male with type 2 diabetes and chronic kidney disease (baseline creatinine 2.2 mg/dL) undergoes cardiac catheterization with iodinated contrast media. Forty-eight hours later, his creatinine peaks at 3.9 mg/dL.

The pathophysiology of this patient's contrast-induced nephropathy involves a combination of what two primary intrarenal mechanisms?

  1. Immune complex deposition in the glomeruli and activation of complement.
  2. Intense medullary vasoconstriction and direct tubular epithelial cell toxicity. (correct answer)
  3. Obstruction from precipitated uric acid crystals and interstitial inflammation.
  4. Afferent arteriole dilation and efferent arteriole constriction causing hyperfiltration.
Explanation: Contrast-induced nephropathy (CIN), a form of ATN, has a dual mechanism of injury. First, the contrast agents cause profound vasoconstriction of the medullary blood vessels (vasa recta), leading to medullary hypoxia and ischemia. Second, the contrast media has a direct cytotoxic effect on renal tubular cells, generating reactive oxygen species and inducing apoptosis. This combination of ischemia and direct toxicity leads to AKI.

Question 17

A 28-year-old woman develops a morbilliform rash, a fever of 38.5°C, and joint pains ten days after starting a course of penicillin for a throat infection. Laboratory work reveals a serum creatinine of 3.1 mg/dL (baseline 0.8 mg/dL) and peripheral eosinophilia. Her urinalysis shows white blood cell casts.

Given this clinical presentation, the patient's acute kidney injury is best classified as which type?

  1. Prerenal azotemia due to septic physiology from the initial infection.
  2. Intrarenal AKI due to drug-induced acute interstitial nephritis. (correct answer)
  3. Intrarenal AKI due to post-infectious glomerulonephritis.
  4. Postrenal AKI due to sulfonamide crystal-induced obstruction.
Explanation: The patient's presentation with the classic triad of fever, rash, and arthralgia, combined with the timing after drug initiation, peripheral eosinophilia, and urinalysis showing white blood cell casts (and likely eosinophiluria), is pathognomonic for acute interstitial nephritis (AIN). AIN is a type of intrarenal AKI caused by an allergic, inflammatory infiltrate in the renal interstitium, most commonly triggered by medications like penicillins.

Question 18

A patient with congestive heart failure relies on renal prostaglandin synthesis to maintain renal blood flow. The addition of which medication would most likely precipitate a prerenal AKI by interfering with this compensatory mechanism?

  1. Spironolactone
  2. Lisinopril
  3. Naproxen (correct answer)
  4. Amlodipine
Explanation: In states of low effective circulating volume like heart failure, the kidneys produce prostaglandins (PGE2, PGI2) to vasodilate the afferent arteriole and preserve renal blood flow and GFR. Naproxen, a non-steroidal anti-inflammatory drug (NSAID), inhibits cyclooxygenase (COX) enzymes, thereby blocking prostaglandin synthesis. This leads to unopposed afferent arteriolar vasoconstriction, a sharp decrease in renal blood flow, and a prerenal AKI.

Question 19

A 52-year-old woman with a history of metastatic cervical cancer treated with pelvic radiation presents with progressive fatigue and nausea. Her creatinine is 5.1 mg/dL. A renal ultrasound demonstrates bilateral hydronephrosis and hydroureter down to the level of the pelvic brim.

This patient's acute kidney injury is best categorized by which underlying mechanism?

  1. Prerenal, due to chemotherapy-induced vomiting and dehydration.
  2. Intrarenal, due to radiation nephritis causing parenchymal damage.
  3. Intrarenal, due to paraneoplastic glomerulonephritis.
  4. Postrenal, due to extrinsic compression of the ureters. (correct answer)
Explanation: The key finding is bilateral hydronephrosis and hydroureter on ultrasound, which is diagnostic of urinary outflow obstruction. Given her history of metastatic cervical cancer and pelvic radiation, the most likely cause is extrinsic compression of both ureters by a tumor mass or radiation-induced fibrosis. Obstruction of urine flow from both kidneys leads to an increase in intratubular pressure, opposing glomerular filtration and causing a postrenal AKI.

Question 20

A patient with decompensated cirrhosis, ascites, and peripheral edema develops worsening renal function (hepatorenal syndrome). Despite having a high total body fluid volume, his renal physiology mimics that of severe volume depletion.

This patient's condition is best classified as which type of AKI?

  1. Prerenal AKI, due to profound splanchnic vasodilation and reduced effective arterial volume. (correct answer)
  2. Intrarenal AKI, due to direct toxicity of bilirubin on the tubular epithelium.
  3. Postrenal AKI, due to high intra-abdominal pressure from ascites compressing the ureters.
  4. Intrarenal AKI, due to IgA nephropathy commonly associated with liver disease.
Explanation: Hepatorenal syndrome is a form of prerenal AKI. In advanced cirrhosis, portal hypertension causes massive vasodilation in the splanchnic (intestinal) circulation. This leads to arterial underfilling and a severely reduced 'effective' circulating volume, which is the volume actually perfusing vital organs. The kidneys sense this profound hypoperfusion and activate the renin-angiotensin-aldosterone system, leading to intense renal vasoconstriction and a fall in GFR, even though the patient's total body volume is high.