Internal Medicine Exam Nephrology and Kidney Injury 5 — Questions and Answers
Question 1: A 42-year-old woman with a history of nephrolithiasis has urine pH persistently above 6.5, serum bicarbonate of 18 mEq/L, and normal anion gap metabolic acidosis. Urine anion gap is positive. What is the diagnosis?
- Proximal (Type II) renal tubular acidosis
- Distal (Type I) renal tubular acidosis (Correct answer)
- Type IV renal tubular acidosis
- Diarrhea-associated metabolic acidosis
Correct answer: Distal (Type I) renal tubular acidosis
Distal RTA is characterized by inability to acidify urine below pH 5.5, positive urine anion gap, normal anion gap acidosis, and predisposition to calcium phosphate nephrolithiasis.
Question 2: A 55-year-old man on hemodialysis three times weekly complains of pruritus, bone pain, and a palpable neck mass. His PTH is 1,200 pg/mL and calcium is 10.8 mg/dL. What is the best treatment?
- Increase dialysis frequency
- Parathyroidectomy (Correct answer)
- Start cinacalcet (calcimimetic)
- Increase phosphate binders
Correct answer: Parathyroidectomy
Tertiary hyperparathyroidism with autonomous PTH secretion, hypercalcemia, and PTH >800 pg/mL refractory to medical therapy requires parathyroidectomy.
Question 3: A 33-year-old woman presents with bilateral renal masses on ultrasound and a family history of early-onset renal cell carcinoma, pheochromocytoma, and retinal hemangioblastomas. Which genetic syndrome is most likely?
- Tuberous sclerosis complex
- Von Hippel-Lindau disease (Correct answer)
- ADPKD (autosomal dominant polycystic kidney disease)
- Hereditary papillary RCC syndrome
Correct answer: Von Hippel-Lindau disease
Von Hippel-Lindau disease (VHL mutation) causes clear cell RCC, pheochromocytoma, hemangioblastomas, and pancreatic cysts with autosomal dominant inheritance.
Question 4: A 70-year-old man with BPH undergoes bilateral hydronephrosis relief by Foley catheter insertion. Over the next 24 hours he produces 8 liters of urine and his creatinine falls from 8.2 to 3.1 mg/dL. What electrolyte abnormality requires monitoring?
- Hyperkalemia from tubular injury
- Hypocalcemia from hungry bone syndrome
- Hyponatremia from free water retention
- Hypokalemia and hyponatremia from post-obstructive diuresis (Correct answer)
Correct answer: Hypokalemia and hyponatremia from post-obstructive diuresis
Post-obstructive diuresis causes massive urinary losses of sodium, potassium, and water; close monitoring and replacement are required to prevent dangerous electrolyte depletion.
Question 5: A 48-year-old man with cirrhosis develops AKI with creatinine rising to 3.4 mg/dL. Urine sodium is 8 mEq/L and urinalysis is bland. He does not respond to 1.5 L albumin infusion. What is the next step?
- Initiate hemodialysis
- Start terlipressin and albumin (Correct answer)
- Perform renal biopsy
- Administer furosemide to improve urine output
Correct answer: Start terlipressin and albumin
Hepatorenal syndrome type 1 (HRS-AKI) is treated with vasoconstrictors (terlipressin preferred in US; norepinephrine as alternative) plus albumin to restore effective circulating volume.
Question 6: A patient with ESRD on peritoneal dialysis develops fever, abdominal pain, and cloudy dialysate. Dialysate WBC count is 380 cells/µL (>50% neutrophils). Gram stain is negative. What is the most likely organism?
- Pseudomonas aeruginosa
- Staphylococcus epidermidis (Correct answer)
- Candida albicans
- Mycobacterium tuberculosis
Correct answer: Staphylococcus epidermidis
Coagulase-negative staphylococci (S. epidermidis) are the most common cause of peritoneal dialysis-associated peritonitis, typically from touch contamination.
Question 7: A 52-year-old woman with rheumatoid arthritis on long-term NSAIDs has a GFR of 35 mL/min/1.73m². Renal biopsy reveals interstitial fibrosis, tubular atrophy, and minimal inflammation. What pattern does this represent?
- Acute allergic interstitial nephritis
- Chronic analgesic nephropathy (chronic interstitial nephritis) (Correct answer)
- Membranous nephropathy
- Focal segmental glomerulosclerosis
Correct answer: Chronic analgesic nephropathy (chronic interstitial nephritis)
Long-term NSAID/analgesic use causes chronic interstitial nephritis with interstitial fibrosis and tubular atrophy, often progressing silently to CKD.
Internal Medicine Exam Nephrology and Kidney Injury 5
A 42-year-old woman with a history of nephrolithiasis has urine pH persistently above 6.5, serum bicarbonate of 18 mEq/L, and normal anion gap metabolic acidosis.
Urine anion gap is positive.
What is the diagnosis?