ABIM Nephrology 1 — Questions and Answers
Question 1: A 60-year-old diabetic patient has proteinuria of 3.5 g/day, hypoalbuminemia, and peripheral edema. Serum creatinine is normal. What is the diagnosis?
- Nephritic syndrome
- Nephrotic syndrome (Correct answer)
- Acute tubular necrosis
- Prerenal azotemia
Correct answer: Nephrotic syndrome
Nephrotic syndrome is defined by proteinuria >3.5 g/day, hypoalbuminemia, edema, and hyperlipidemia, often with lipiduria.
Question 2: A patient presents with oliguria after surgery. BUN is 42 mg/dL, creatinine is 1.4 mg/dL (BUN:Cr ratio = 30). Urine sodium is 8 mEq/L and FENa is 0.5%. What is the most likely diagnosis?
- Acute tubular necrosis
- Prerenal azotemia (Correct answer)
- Postrenal obstruction
- Glomerulonephritis
Correct answer: Prerenal azotemia
Prerenal azotemia is characterized by elevated BUN:Cr ratio (>20), low urine sodium (<20 mEq/L), and FENa <1%, reflecting intact tubular function with avid sodium reabsorption.
Question 3: A patient with CKD stage 4 has a serum potassium of 6.2 mEq/L with peaked T waves on ECG. What is the immediate treatment?
- Sodium polystyrene sulfonate
- Kayexalate enema
- IV calcium gluconate (Correct answer)
- Furosemide IV
Correct answer: IV calcium gluconate
IV calcium gluconate stabilizes the cardiac membrane immediately in hyperkalemia with ECG changes, though it does not lower potassium levels.
Question 4: Which acid-base disorder is most commonly associated with diarrhea?
- Metabolic alkalosis
- Respiratory acidosis
- Non-anion gap metabolic acidosis (Correct answer)
- High anion gap metabolic acidosis
Correct answer: Non-anion gap metabolic acidosis
Diarrhea causes loss of bicarbonate-rich intestinal secretions, resulting in non-anion gap (hyperchloremic) metabolic acidosis.
Question 5: A 35-year-old woman with SLE develops nephrotic-range proteinuria and hematuria. Renal biopsy shows wire-loop lesions on light microscopy. What is the most likely diagnosis?
- Focal segmental glomerulosclerosis
- Membranous nephropathy
- Lupus nephritis class IV (diffuse proliferative) (Correct answer)
- IgA nephropathy
Correct answer: Lupus nephritis class IV (diffuse proliferative)
Wire-loop lesions on renal biopsy represent subendothelial immune complex deposits and are pathognomonic of diffuse proliferative (class IV) lupus nephritis.
Question 6: Which medication should be avoided or dose-adjusted in a patient with GFR of 20 mL/min/1.73m²?
- Amlodipine
- Metformin (Correct answer)
- Ondansetron
- Acetaminophen
Correct answer: Metformin
Metformin is contraindicated when GFR <30 mL/min due to the risk of lactic acidosis from drug accumulation in the setting of reduced renal clearance.
ABIM Nephrology 1
A 60-year-old diabetic patient has proteinuria of 3.5 g/day, hypoalbuminemia, and peripheral edema.
Serum creatinine is normal.
What is the diagnosis?