ABIM Nephrology 2 — Questions and Answers
Question 1: A patient with a history of recurrent kidney stones has 24-hour urine showing hypercalciuria with normal serum calcium. What is the most likely diagnosis?
- Primary hyperparathyroidism
- Sarcoidosis
- Idiopathic hypercalciuria (Correct answer)
- Vitamin D toxicity
Correct answer: Idiopathic hypercalciuria
Idiopathic hypercalciuria (with normal serum calcium) is the most common cause of calcium oxalate nephrolithiasis and is treated with thiazide diuretics.
Question 2: A 50-year-old man with polycystic kidney disease asks about his prognosis. His father died from a ruptured cerebral aneurysm. What screening should be offered?
- Annual renal ultrasound
- MRA of the cerebral vasculature (Correct answer)
- Genetic testing for PKD1 mutation
- 24-hour urine protein
Correct answer: MRA of the cerebral vasculature
Patients with ADPKD and a family history of intracranial aneurysm should undergo MRA screening for cerebral aneurysms due to the increased familial risk.
Question 3: Which finding best distinguishes acute tubular necrosis (ATN) from prerenal azotemia?
- Elevated serum creatinine
- Muddy brown granular casts in urine (Correct answer)
- Decreased urine output
- Elevated BUN
Correct answer: Muddy brown granular casts in urine
Muddy brown granular casts (renal tubular epithelial cell casts) in the urine are pathognomonic of ATN and reflect tubular epithelial cell injury and sloughing.
Question 4: A patient with end-stage renal disease on hemodialysis develops itching, periorbital edema, and a facial rash with hypercalcemia. Serum PTH is very low. What is the diagnosis?
- Secondary hyperparathyroidism
- Adynamic bone disease (Correct answer)
- Calciphylaxis
- Aluminum toxicity
Correct answer: Adynamic bone disease
Adynamic bone disease in ESRD patients is characterized by low PTH, impaired bone turnover, and often results from over-suppression of PTH with calcium or vitamin D therapy.
Question 5: A patient has an anion gap of 22 mEq/L, arterial pH of 7.28, and serum bicarbonate of 14 mEq/L. Which condition is NOT a cause of high anion gap metabolic acidosis?
- Diabetic ketoacidosis
- Lactic acidosis
- Diarrhea (Correct answer)
- Renal failure
Correct answer: Diarrhea
Diarrhea causes a non-anion gap (normal anion gap, hyperchloremic) metabolic acidosis due to bicarbonate loss, not accumulation of unmeasured anions.
Question 6: A 40-year-old woman with nephrotic syndrome due to minimal change disease (MCD) fails to respond to two courses of prednisone. What is the next treatment?
- Mycophenolate mofetil
- Cyclophosphamide
- Rituximab
- Cyclosporine (Correct answer)
Correct answer: Cyclosporine
For frequently relapsing or steroid-dependent MCD, calcineurin inhibitors (cyclosporine or tacrolimus) are the next line of therapy after steroid failure.
ABIM Nephrology 2
A patient with a history of recurrent kidney stones has 24-hour urine showing hypercalciuria with normal serum calcium.
What is the most likely diagnosis?