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ABIM Nephrology study materials
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ABIM Nephrology practice questions

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Question 1Glomerular Disease

A 28-year-old man presents with hematuria, hypertension, and a serum creatinine of 1.8 mg/dL two weeks after an upper respiratory infection. Serology shows low C3. Renal biopsy demonstrates mesangial IgA deposits on immunofluorescence. Which diagnosis is most likely?

  1. Post-infectious glomerulonephritis
  2. Membranous nephropathy
  3. Minimal change disease
  4. IgA nephropathy Correct answer.

Explanation

IgA nephropathy classically presents with episodic gross hematuria concurrent with or shortly after mucosal infections, and biopsy shows dominant mesangial IgA deposits. Complement levels are usually normal, though low C3 can occur.

Question 2Glomerular Disease

Which serologic marker is most characteristic of primary membranous nephropathy?

  1. Anti-glomerular basement membrane antibody
  2. Anti-neutrophil cytoplasmic antibody
  3. Anti-double-stranded DNA antibody
  4. Anti-phospholipase A2 receptor antibody Correct answer.

Explanation

Anti-phospholipase A2 receptor antibodies are found in roughly 70-80% of primary membranous nephropathy and help distinguish it from secondary causes. The other antibodies are associated with different glomerular or systemic diseases.

Question 3Glomerular Disease

A 7-year-old boy presents with periorbital edema, proteinuria of 9 g/day, and a normal serum albumin otherwise. Biopsy shows normal glomeruli on light microscopy with effacement of podocyte foot processes on electron microscopy. Which therapy is first-line for the initial episode?

  1. Calcineurin inhibitor
  2. Rituximab
  3. High-dose corticosteroids Correct answer.
  4. Cyclophosphamide

Explanation

Minimal change disease is the most common cause of childhood nephrotic syndrome and is typically steroid-responsive, so high-dose corticosteroids are first-line. Cytotoxic and biologic agents are reserved for steroid-dependent or frequently relapsing disease.

Question 4Glomerular Disease

Which pattern of immunofluorescence is characteristic of anti-glomerular basement membrane disease?

  1. Linear IgG along the glomerular basement membrane Correct answer.
  2. Pauci-immune staining with minimal immunoglobulin
  3. Subepithelial humps with C3 dominance
  4. Granular IgG and C3 in the mesangium

Explanation

Anti-GBM antibodies bind uniformly along the basement membrane, producing a smooth linear IgG pattern on immunofluorescence. Granular and pauci-immune patterns reflect immune-complex and ANCA-associated disease respectively.

Question 5Glomerular Disease

A patient with nephrotic syndrome undergoes renal biopsy showing segmental sclerosis of some glomeruli with foot process effacement and no immune deposits. Which clinical feature most strongly supports focal segmental glomerulosclerosis over minimal change disease?

  1. Presence of hypertension and reduced GFR Correct answer.
  2. Onset in childhood
  3. Rapid response to corticosteroids
  4. Selective proteinuria

Explanation

FSGS more often presents with hypertension, reduced GFR, and nonselective proteinuria, whereas minimal change disease typically has preserved renal function and selective proteinuria. Steroid responsiveness also favors minimal change disease.

Question 6Glomerular Disease

A 45-year-old woman with recent sore throat develops hematuria, edema, and hypertension. Labs show low C3, and biopsy reveals subepithelial humps with granular C3 deposition. Which finding is most consistent with the underlying mechanism?

  1. Amyloid fibrils in the mesangium
  2. Pauci-immune crescent formation without deposits
  3. Nephritogenic streptococcal antigens forming immune complexes Correct answer.
  4. Antibodies directed against phospholipase A2 receptor

Explanation

Post-infectious glomerulonephritis results from deposition of circulating or in situ immune complexes containing streptococcal antigens, producing subepithelial humps and low complement. This differs mechanistically from the other options.

Question 7Glomerular Disease

Which serologic finding is most specific for systemic lupus erythematosus among patients presenting with nephritic syndrome and a full-house immunofluorescence pattern?

  1. Anti-Sm antibody Correct answer.
  2. Anti-histone antibody
  3. Anti-centromere antibody
  4. Rheumatoid factor

Explanation

Anti-Sm antibodies are highly specific for SLE, and full-house immunofluorescence (IgG, IgA, IgM, C3, C1q) is characteristic of lupus nephritis. Anti-histone antibodies are sensitive but not specific.

Question 8Glomerular Disease

A 62-year-old man presents with hemoptysis, hematuria, and a rising creatinine. Serology is positive for anti-GBM antibodies. Which additional test should be obtained because of the strong association with this condition?

  1. Hepatitis C RNA
  2. Serum free light chains
  3. Anti-neutrophil cytoplasmic antibody Correct answer.
  4. Anti-phospholipase A2 receptor antibody

Explanation

A substantial proportion of patients with anti-GBM disease also have circulating ANCA, which affects prognosis and management. Testing for ANCA is therefore standard in this setting.

Question 9Glomerular Disease

A patient with known hepatitis B infection develops nephrotic syndrome. Biopsy shows thickened capillary loops with subepithelial deposits and spike formation on silver stain. Which secondary cause is most likely?

  1. Membranous nephropathy Correct answer.
  2. Fibrillary glomerulonephritis
  3. Membranoproliferative glomerulonephritis
  4. IgA nephropathy

Explanation

Hepatitis B is a well-recognized secondary cause of membranous nephropathy, which shows subepithelial deposits and spike formation on silver stain. Other infections such as hepatitis C are more associated with MPGN.

Question 10Glomerular Disease

Which laboratory finding best distinguishes nephritic from nephrotic syndrome in a patient presenting with edema and hematuria?

  1. Urinary red blood cell casts with mild proteinuria Correct answer.
  2. Serum albumin below 2.5 g/dL
  3. Proteinuria exceeding 3.5 g/day
  4. Total cholesterol above 300 mg/dL

Explanation

Nephritic syndrome is characterized by an active urinary sediment including dysmorphic red cells and red cell casts, usually with subnephrotic proteinuria. Nephrotic syndrome is defined by heavy proteinuria and hypoalbuminemia.

Question 11Glomerular Disease

A 34-year-old woman with a history of recurrent sinusitis and purulent nasal discharge presents with hematuria and a creatinine of 2.4 mg/dL. ANCA testing is positive for anti-PR3. Which diagnosis is most likely?

  1. IgA vasculitis
  2. Anti-GBM disease
  3. Cryoglobulinemic vasculitis
  4. Granulomatosis with polyangiitis Correct answer.

Explanation

Granulomatosis with polyangiitis is an ANCA-associated vasculitis that typically involves the upper respiratory tract and kidneys, and anti-PR3 antibodies are highly specific. Pauci-immune crescentic glomerulonephritis is the typical renal lesion.

Question 12Glomerular Disease

Which morphologic finding on renal biopsy is most characteristic of membranoproliferative glomerulonephritis?

  1. Mesangial widening with IgA deposits
  2. Effacement of podocyte foot processes only
  3. Tram-track appearance of the glomerular basement membrane Correct answer.
  4. Linear IgG along the basement membrane

Explanation

MPGN shows mesangial cell proliferation with interposition of mesangial matrix into the capillary wall, creating the tram-track appearance on silver stain. The other findings belong to different glomerular diseases.

Question 13Glomerular Disease

A patient with nephrotic syndrome is found to have low serum C3 with normal C4, and biopsy shows dense deposits within the glomerular basement membrane. Which diagnosis is most likely?

  1. Cryoglobulinemic glomerulonephritis
  2. Lupus nephritis
  3. IgA nephropathy
  4. C3 glomerulopathy Correct answer.

Explanation

C3 glomerulopathy results from dysregulation of the alternative complement pathway, producing low C3 with normal C4 and dense deposits on electron microscopy. Lupus and cryoglobulinemic disease typically activate the classical pathway with low C4 as well.

Question 14Glomerular Disease

A 58-year-old man with long-standing type 2 diabetes has proteinuria and a rising creatinine. Which biopsy finding would most strongly suggest a diagnosis other than diabetic nephropathy?

  1. Diffuse foot process effacement with no immune deposits
  2. Uniform basement membrane thickening
  3. Crescents in multiple glomeruli Correct answer.
  4. Nodular mesangial expansion

Explanation

Crescent formation indicates an active proliferative glomerulonephritis and is not part of diabetic nephropathy, prompting reconsideration of the diagnosis. Nodular expansion, basement membrane thickening, and foot process effacement are all compatible with diabetic kidney disease.

Question 15Glomerular Disease

Which statement about the treatment of primary membranous nephropathy is most accurate?

  1. Supportive care with renin-angiotensin blockade is appropriate for low-risk disease. Correct answer.
  2. Corticosteroid monotherapy reliably induces remission.
  3. Rituximab is contraindicated in this condition.
  4. All patients require immediate cytotoxic therapy at diagnosis.

Explanation

Many patients with primary membranous nephropathy have indolent disease and can be managed with supportive care including ACE inhibitors or ARBs while monitoring. Immunosuppression is reserved for those at higher risk of progression.

Question 16Glomerular Disease

Which of the following is the most common cause of nephrotic syndrome in adults in developed countries?

  1. Focal segmental glomerulosclerosis Correct answer.
  2. Minimal change disease
  3. IgA nephropathy
  4. Membranous nephropathy

Explanation

FSGS is among the most common primary glomerular causes of nephrotic syndrome in adults, and its incidence has risen in many populations. IgA nephropathy more often presents with nephritic features.

Question 17Glomerular Disease

A patient with IgA nephropathy has persistent proteinuria of 1.5 g/day despite blood pressure control. Which medication class provides both renin-angiotensin blockade and antiproteinuric benefit as first-line therapy?

  1. Loop diuretics
  2. Thiazide diuretics
  3. Angiotensin-converting enzyme inhibitors Correct answer.
  4. Beta-blockers

Explanation

ACE inhibitors reduce intraglomerular pressure and proteinuria and are first-line for proteinuric IgA nephropathy, with ARBs as an alternative. Diuretics and beta-blockers do not provide comparable antiproteinuric effects.

Question 18Glomerular Disease

A 25-year-old woman with SLE develops proteinuria of 4 g/day and active urinary sediment. Biopsy shows diffuse proliferative glomerulonephritis with endocapillary proliferation and crescents. Which class of lupus nephritis is this?

  1. Class II
  2. Class V
  3. Class III
  4. Class IV Correct answer.

Explanation

Diffuse proliferative lupus nephritis involving more than 50% of glomeruli is class IV and carries the highest risk of progression without treatment. Class III is focal, and class V is membranous.

Question 19Glomerular Disease

Which infection is most classically associated with the development of cryoglobulinemic membranoproliferative glomerulonephritis?

  1. Hepatitis C virus Correct answer.
  2. Human immunodeficiency virus
  3. Hepatitis B virus
  4. Streptococcus pyogenes

Explanation

Chronic hepatitis C infection is the most common cause of mixed cryoglobulinemia, which deposits in glomeruli and produces an MPGN pattern. Hepatitis B is more associated with membranous nephropathy.

Question 20Glomerular Disease

A patient presents with nephrotic syndrome, and biopsy reveals apple-green birefringence under polarized light with Congo red staining. Which underlying process is most likely?

  1. Podocyte injury from a circulating permeability factor
  2. Amyloid fibril deposition Correct answer.
  3. Immune complex deposition
  4. Complement dysregulation

Explanation

Congo red staining with apple-green birefringence under polarized light identifies amyloid deposits, which can cause nephrotic-range proteinuria. This is distinct from immune-complex, podocytopathic, or complement-mediated disease.

Question 21Glomerular Disease

A patient with IgA nephropathy has an eGFR of 45 mL/min/1.73 m² and proteinuria of 2 g/day despite maximal renin-angiotensin blockade. Which additional agent has been shown to reduce proteinuria and slow progression in this setting?

  1. Alpha-blocker
  2. Loop diuretic
  3. Sodium-glucose cotransporter-2 inhibitor Correct answer.
  4. Calcium channel blocker

Explanation

SGLT2 inhibitors reduce proteinuria and slow CKD progression when added to renin-angiotensin blockade in proteinuric kidney disease, including IgA nephropathy. The other agents do not confer this kidney-protective effect.

Question 22Glomerular Disease

Which finding on urinalysis most specifically indicates a glomerular source of hematuria?

  1. White blood cell casts
  2. Dysmorphic red blood cells and red blood cell casts Correct answer.
  3. Triple phosphate crystals
  4. Isomorphic red blood cells

Explanation

Dysmorphic red cells and red cell casts indicate bleeding from the glomerulus, where red cells are deformed passing through the basement membrane and molded into casts. Isomorphic red cells suggest a lower urinary tract source.

Question 23Glomerular Disease

A patient with anti-GBM disease presents with dialysis-dependent renal failure and pulmonary hemorrhage. Which treatment combination is standard of care?

  1. Plasmapheresis, cyclophosphamide, and corticosteroids Correct answer.
  2. Corticosteroids alone
  3. Rituximab monotherapy
  4. Angiotensin-converting enzyme inhibitor and statin

Explanation

Anti-GBM disease is treated with plasmapheresis to remove circulating antibodies combined with cyclophosphamide and corticosteroids to suppress new antibody production. Prompt initiation improves renal outcomes.

Question 24Glomerular Disease

Which feature best distinguishes IgA vasculitis (Henoch-Schönlein purpura) from IgA nephropathy?

  1. Systemic small-vessel involvement with palpable purpura Correct answer.
  2. Occurrence in children
  3. Elevated serum IgA levels
  4. Presence of mesangial IgA deposits

Explanation

IgA vasculitis and IgA nephropathy share mesangial IgA deposition, but IgA vasculitis involves systemic small vessels, producing palpable purpura, arthritis, and abdominal pain. Both can occur in children and both may show elevated serum IgA.

Question 25Tubulointerstitial and Vascular Disease

A 24-year-old woman presents with flank pain, fever, and dysuria. Urinalysis shows pyuria and white cell casts. She is diagnosed with acute pyelonephritis. Which of the following is the most common predisposing factor for acute pyelonephritis in young women?

  1. Diabetes mellitus
  2. Vesicoureteral reflux
  3. Sexual intercourse Correct answer.
  4. Urinary tract obstruction

Explanation

Acute pyelonephritis in young women is most often caused by ascending infection from the bladder, and sexual intercourse is a well-established risk factor for ascending urinary tract infection. Vesicoureteral reflux and obstruction are more common predisposing factors in children and older adults, respectively.

Question 26Tubulointerstitial and Vascular Disease

A 45-year-old man with a history of recurrent calcium oxalate kidney stones presents with acute flank pain and hematuria. Imaging reveals a 6-mm stone in the left ureter causing obstruction. Which of the following is the most likely finding on urinalysis?

  1. White blood cell casts
  2. Red blood cells without red blood cell casts Correct answer.
  3. Muddy brown casts
  4. Hyaline casts

Explanation

A ureteral stone can irritate and injure the urinary tract, producing hematuria with free red blood cells. Red blood cell casts instead suggest bleeding within renal tubules from a glomerular process and are not the characteristic stone finding.

Question 27Tubulointerstitial and Vascular Disease

A 62-year-old man with a history of hypertension and diabetes presents with acute kidney injury. He has been taking an NSAID for back pain. His urinalysis shows muddy brown casts. Which of the following is the most likely diagnosis?

  1. Acute interstitial nephritis
  2. Acute tubular necrosis Correct answer.
  3. Glomerulonephritis
  4. Prerenal azotemia

Explanation

Muddy brown casts are characteristic of acute tubular necrosis, which can be caused by nephrotoxic agents such as NSAIDs, especially in patients with underlying kidney disease. Acute interstitial nephritis typically presents with white blood cell casts and eosinophiluria.

Question 28Tubulointerstitial and Vascular Disease

A 30-year-old woman is diagnosed with acute interstitial nephritis due to NSAID use. Which of the following is the most characteristic finding on urinalysis?

  1. White blood cell casts Correct answer.
  2. Muddy brown casts
  3. Red blood cell casts
  4. Fatty casts

Explanation

Acute interstitial nephritis is characterized by sterile pyuria and white blood cell casts. Eosinophiluria may also be present but is less sensitive and specific.

Question 29Tubulointerstitial and Vascular Disease

A 55-year-old man with a history of hypertension presents with acute flank pain and a rise in serum creatinine. He is found to have bilateral renal artery stenosis due to atherosclerosis. Which of the following medications is most likely to precipitate acute kidney injury in this patient?

  1. Metoprolol
  2. Amlodipine
  3. Lisinopril Correct answer.
  4. Furosemide

Explanation

Angiotensin-converting enzyme inhibitors can precipitate acute kidney injury in patients with bilateral renal artery stenosis by reducing glomerular filtration pressure. Calcium channel blockers, loop diuretics, and beta-blockers are generally safe.

Question 30Tubulointerstitial and Vascular Disease

A 68-year-old man with a history of smoking presents with new-onset hypertension and worsening renal function. He is found to have a serum creatinine of 2.5 mg/dL. Renal ultrasound shows a small right kidney and a normal-sized left kidney. Which of the following is the most appropriate diagnostic test to confirm the diagnosis?

  1. Captopril renography
  2. Magnetic resonance angiography
  3. Renal arteriography Correct answer.
  4. Renal artery duplex ultrasonography

Explanation

Renal arteriography is the gold standard for diagnosing renal artery stenosis and can be performed with carbon dioxide or gadolinium to avoid nephrotoxicity. Duplex ultrasonography and magnetic resonance angiography are noninvasive screening tests but have limitations.

Question 31Tubulointerstitial and Vascular Disease

A 45-year-old woman with a history of recurrent urinary tract infections presents with fever, flank pain, and a serum creatinine of 1.8 mg/dL. Urinalysis shows pyuria and white blood cell casts. She is diagnosed with acute pyelonephritis. Which of the following is the most appropriate initial antibiotic regimen?

  1. Intravenous ceftriaxone Correct answer.
  2. Oral ciprofloxacin
  3. Intravenous vancomycin
  4. Oral nitrofurantoin

Explanation

For acute pyelonephritis requiring hospitalization or with systemic symptoms, intravenous antibiotics such as ceftriaxone are appropriate. Oral ciprofloxacin may be used for outpatient management of uncomplicated pyelonephritis, but this patient has impaired renal function and systemic symptoms.

Question 32Tubulointerstitial and Vascular Disease

A 60-year-old man with a history of gout presents with acute monoarthritis of the first metatarsophalangeal joint. He has a serum creatinine of 2.0 mg/dL. Which of the following medications is contraindicated in this patient?

  1. Colchicine
  2. Probenecid Correct answer.
  3. Allopurinol
  4. Febuxostat

Explanation

Probenecid is a uricosuric agent that increases uric acid excretion and is contraindicated in patients with chronic kidney disease (creatinine clearance <50 mL/min) because of reduced efficacy and risk of uric acid stones. Colchicine, allopurinol, and febuxostat can be used with dose adjustments.

Question 33Tubulointerstitial and Vascular Disease

A 35-year-old woman presents with hematuria, flank pain, and a serum creatinine of 1.5 mg/dL. She has a history of recurrent aphthous ulcers and genital ulcers. Which of the following is the most likely diagnosis?

  1. Henoch-Schönlein purpura
  2. Behçet disease Correct answer.
  3. IgA nephropathy
  4. Systemic lupus erythematosus

Explanation

Behçet disease is a systemic vasculitis that can cause renal involvement, including glomerulonephritis, and is characterized by recurrent oral and genital ulcers. IgA nephropathy typically presents with hematuria after an upper respiratory infection, without genital ulcers.

Question 34Tubulointerstitial and Vascular Disease

A 50-year-old man with a history of hypertension and chronic kidney disease presents with acute kidney injury. He has been taking a proton pump inhibitor for gastroesophageal reflux disease. His urinalysis shows white blood cell casts and eosinophiluria. Which of the following is the most likely diagnosis?

  1. Prerenal azotemia
  2. Acute tubular necrosis
  3. Acute interstitial nephritis Correct answer.
  4. Glomerulonephritis

Explanation

Proton pump inhibitors are a common cause of drug-induced acute interstitial nephritis, which is characterized by white blood cell casts and eosinophiluria. Acute tubular necrosis typically shows muddy brown casts.

Question 35Tubulointerstitial and Vascular Disease

A 70-year-old man with a history of hypertension and diabetes presents with a serum creatinine of 3.0 mg/dL. He has been taking an ACE inhibitor and a thiazide diuretic. Renal ultrasound shows bilateral small kidneys. Which of the following is the most likely cause of his chronic kidney disease?

  1. Renal artery stenosis
  2. Diabetic nephropathy
  3. Hypertensive nephrosclerosis Correct answer.
  4. Chronic interstitial nephritis

Explanation

Hypertensive nephrosclerosis is a common cause of chronic kidney disease in older adults with long-standing hypertension and is characterized by bilateral small kidneys. Diabetic nephropathy typically presents with proteinuria and may not cause small kidneys until late stages.

Question 36Tubulointerstitial and Vascular Disease

A 28-year-old woman presents with hematuria and flank pain. She has a history of recurrent kidney stones. Genetic testing reveals a mutation in the SLC3A1 gene. Which of the following is the most likely diagnosis?

  1. Primary hyperoxaluria
  2. Lesch-Nyhan syndrome
  3. Cystinuria Correct answer.
  4. Distal renal tubular acidosis

Explanation

Cystinuria is caused by mutations in the SLC3A1 or SLC7A9 genes, leading to impaired renal reabsorption of cystine and causing recurrent cystine stones. Primary hyperoxaluria is due to enzyme deficiencies in glyoxylate metabolism.

Question 37Tubulointerstitial and Vascular Disease

A 65-year-old woman with a history of hypertension and chronic kidney disease presents with acute kidney injury. She has been taking an NSAID and an ACE inhibitor. Her urinalysis shows muddy brown casts. Which of the following is the most likely mechanism of her acute kidney injury?

  1. Ischemic tubular injury Correct answer.
  2. Glomerular immune complex deposition
  3. Acute interstitial inflammation
  4. Urinary tract obstruction

Explanation

The combination of an NSAID and an ACE inhibitor can cause acute kidney injury via hemodynamic effects, leading to ischemic acute tubular necrosis, which is characterized by muddy brown casts. Acute interstitial nephritis would show white blood cell casts.

Question 38Tubulointerstitial and Vascular Disease

A 40-year-old man presents with acute kidney injury and a rash. He has been taking allopurinol for gout. His urinalysis shows white blood cell casts and eosinophiluria. Which of the following is the most likely diagnosis?

  1. IgA nephropathy
  2. Acute interstitial nephritis Correct answer.
  3. Acute tubular necrosis
  4. Thrombotic microangiopathy

Explanation

Allopurinol is a common cause of drug-induced acute interstitial nephritis, which can present with rash, fever, eosinophilia, and acute kidney injury. Urinalysis typically shows white blood cell casts and eosinophiluria.

Question 39Tubulointerstitial and Vascular Disease

A 55-year-old man with a history of hypertension and chronic kidney disease presents with acute kidney injury. He has been taking an ACE inhibitor and a potassium-sparing diuretic. His serum creatinine is 3.5 mg/dL and potassium is 6.0 mEq/L. Which of the following is the most appropriate initial management?

  1. Intravenous insulin and glucose Correct answer.
  2. Oral sodium polystyrene sulfonate
  3. Emergent hemodialysis
  4. Intravenous calcium gluconate

Explanation

Intravenous insulin and glucose is the first-line treatment for hyperkalemia to shift potassium intracellularly, especially in the presence of ECG changes or severe hyperkalemia. Calcium gluconate is used for cardiac membrane stabilization but does not lower potassium.

Question 40Tubulointerstitial and Vascular Disease

A 45-year-old woman with a history of recurrent urinary tract infections presents with fever and flank pain. She is diagnosed with acute pyelonephritis. Blood cultures grow Escherichia coli. Which of the following is the most important virulence factor of E. coli in pyelonephritis?

  1. P fimbriae Correct answer.
  2. K capsule
  3. Endotoxin
  4. Hemolysin

Explanation

P fimbriae are adhesins that allow E. coli to attach to uroepithelial cells and are strongly associated with pyelonephritis. The K capsule and hemolysin contribute to virulence but are less specific for upper urinary tract infection.

Question 41Tubulointerstitial and Vascular Disease

A 60-year-old man with a history of hypertension and chronic kidney disease presents with acute kidney injury. He has been taking an NSAID and an ACE inhibitor. His urinalysis shows muddy brown casts. Which of the following is the most likely mechanism of his acute kidney injury?

  1. Urinary tract obstruction
  2. Acute interstitial inflammation
  3. Glomerular immune complex deposition
  4. Ischemic tubular injury Correct answer.

Explanation

The combination of an NSAID and an ACE inhibitor can cause acute kidney injury via hemodynamic effects, leading to ischemic acute tubular necrosis, which is characterized by muddy brown casts. Acute interstitial nephritis would show white blood cell casts.

Question 42Tubulointerstitial and Vascular Disease

A 50-year-old woman with a history of hypertension and chronic kidney disease presents with acute kidney injury. She has been taking a proton pump inhibitor. Her urinalysis shows white blood cell casts and eosinophiluria. Which of the following is the most likely diagnosis?

  1. Acute interstitial nephritis Correct answer.
  2. Prerenal azotemia
  3. Acute tubular necrosis
  4. Glomerulonephritis

Explanation

Proton pump inhibitors are a common cause of drug-induced acute interstitial nephritis, which is characterized by white blood cell casts and eosinophiluria. Acute tubular necrosis typically shows muddy brown casts.

Question 43Acute Kidney Injury

A 68-year-old man is admitted with 2 days of vomiting and poor oral intake. Serum creatinine is 2.4 mg/dL (baseline 1.0 mg/dL). Urine sodium is 12 mEq/L, urine osmolality is 620 mOsm/kg, and fractional excretion of urea is 28%. Which of the following is the most likely cause of his acute kidney injury?

  1. Acute tubular necrosis
  2. Prerenal hypovolemia Correct answer.
  3. Obstructive uropathy
  4. Acute interstitial nephritis

Explanation

A low urine sodium, concentrated urine, and a fractional excretion of urea below 35% indicate intact tubular sodium and water reabsorption, which is the pattern of a prerenal (volume-depleted) state. These indices lose their reliability once diuretics are used or intrinsic tubular injury develops.

Question 44Acute Kidney Injury

Which urinalysis finding is most characteristic of acute tubular necrosis?

  1. Numerous dysmorphic red cells
  2. Broad, muddy brown granular casts Correct answer.
  3. Calcium oxalate crystals
  4. Sterile pyuria with white cell casts

Explanation

Sloughed tubular epithelial cells form pigmented granular casts that appear muddy brown in the urine sediment of acute tubular necrosis. Dysmorphic red cells indicate glomerular bleeding, white cell casts suggest interstitial inflammation, and oxalate crystals suggest a crystal-related process.

Question 45Acute Kidney Injury

A patient develops acute kidney injury after receiving intravenous contrast. Which of the following best describes the typical clinical course of contrast-associated acute kidney injury?

  1. Creatinine rises within 24 to 72 hours and usually peaks within 3 to 5 days Correct answer.
  2. Creatinine rises only if urine output falls below 400 mL per day
  3. Creatinine rises after 10 to 14 days and rarely recovers
  4. Creatinine rises immediately within 1 hour and normalizes within 24 hours

Explanation

Contrast-associated acute kidney injury typically produces a creatinine rise beginning within 24 to 72 hours, peaking at about 3 to 5 days, and usually resolving within 7 to 10 days. The timing reflects the delay before serum creatinine equilibrates with the fall in glomerular filtration.

Question 46Acute Kidney Injury

Which finding best distinguishes hepatorenal syndrome from other causes of acute kidney injury in a patient with cirrhosis and ascites?

  1. Bilateral hydronephrosis on renal ultrasound
  2. Urine sodium below 10 mEq/L with bland urine sediment and no response to volume expansion Correct answer.
  3. Eosinophiluria with a rising serum creatinine after a new medication
  4. Fractional excretion of sodium above 2% with muddy brown casts

Explanation

Hepatorenal syndrome is a functional, vasoconstrictive renal failure in advanced liver disease, so the urine is sodium-avid with a bland sediment and the kidney does not improve with volume resuscitation. Structural renal disease and obstruction must be excluded before making the diagnosis.

Question 47Acute Kidney Injury

A 72-year-old woman develops acute kidney injury 10 days after starting a proton pump inhibitor. She has a maculopapular rash, fever, and peripheral eosinophilia. Which of the following is the most likely diagnosis?

  1. Acute interstitial nephritis Correct answer.
  2. Acute tubular necrosis
  3. Cholesterol atheroembolism
  4. Thrombotic microangiopathy

Explanation

The triad of rash, fever, and eosinophilia after a new drug, together with acute kidney injury, is classic for acute interstitial nephritis. Proton pump inhibitors are among the most common culprits, and the full triad is present in only a minority of patients.

Question 48Acute Kidney Injury

A 55-year-old man with chronic kidney disease undergoes coronary angiography. Which intervention most reliably reduces the risk of contrast-associated acute kidney injury?

  1. Intravenous isotonic saline volume expansion before and after the procedure Correct answer.
  2. Oral N-acetylcysteine given the night before the procedure
  3. Sodium bicarbonate infusion started after contrast administration
  4. Furosemide with mannitol to maintain high urine output

Explanation

Isotonic intravenous volume expansion is the best-supported preventive measure for contrast-associated acute kidney injury. N-acetylcysteine, bicarbonate strategies, and forced diuresis have not shown consistent benefit and forced diuresis may cause harm.

Question 49Acute Kidney Injury

A 24-year-old man is found unresponsive after a suspected overdose. He has acute kidney injury, an elevated osmolal gap, and abundant calcium oxalate crystals on urinalysis. Which of the following is the most appropriate initial specific therapy?

  1. Fomepizole Correct answer.
  2. N-acetylcysteine
  3. Sodium polystyrene sulfonate
  4. High-dose furosemide

Explanation

The combination of an osmolal gap, acute kidney injury, and calcium oxalate crystalluria suggests ethylene glycol poisoning, for which fomepizole is the first-line antidote because it blocks alcohol dehydrogenase. Hemodialysis is added for severe acidosis or renal failure.

Question 50Acute Kidney Injury

A 60-year-old woman with a recent upper respiratory infection develops acute kidney injury, hypertension, and a serum creatinine of 3.1 mg/dL. Urinalysis shows red cell casts and dysmorphic red cells. Which of the following is the most likely diagnosis?

  1. Prerenal azotemia
  2. Acute tubular necrosis
  3. Papillary necrosis
  4. Glomerulonephritis Correct answer.

Explanation

Red cell casts and dysmorphic red cells indicate glomerular bleeding, which localizes the injury to the glomerulus. Glomerulonephritis often presents with an active urinary sediment, hypertension, and acute kidney injury after an infection.