Internal Medicine Exam Nephrology and Kidney Injury 3

Question 1

A 55-year-old woman with type 2 diabetes has a GFR of 28 mL/min/1.73m² and serum phosphorus of 6.1 mg/dL despite dietary restriction. What is the most appropriate next step?

Accepted Answer

Start sevelamer (non-calcium binder)

Answer

Sevelamer is preferred over calcium-based binders in dialysis-stage CKD to avoid calcium loading and vascular calcification risk.

Question 2

A 40-year-old man is found to have a serum sodium of 118 mEq/L. He has psychogenic polydipsia and appears euvolemic. Which correction rate is safe to prevent osmotic demyelination syndrome?

Accepted Answer

Correct by 8-10 mEq/L in 24 hours

Answer

Safe correction of chronic hyponatremia is limited to 8-10 mEq/L per 24 hours to prevent osmotic demyelination syndrome (central pontine myelinolysis).

Question 3

A 70-year-old man with decompensated heart failure has oliguria, BUN 48 mg/dL, creatinine 2.2 mg/dL, and urine sodium 10 mEq/L. His kidney injury is best classified as:

Accepted Answer

Pre-renal AKI from reduced effective circulating volume

Answer

Low urine sodium (<20 mEq/L) and elevated BUN:creatinine ratio in heart failure indicate pre-renal AKI from reduced effective arterial blood volume.

Question 4

A 50-year-old woman with a history of recurrent UTIs presents with flank pain and imaging showing a staghorn calculus filling the right renal pelvis. Urine culture grows Proteus mirabilis. What type of stone is this?

Accepted Answer

Struvite (magnesium ammonium phosphate)

Answer

Struvite stones form in the setting of urease-producing organisms (Proteus, Klebsiella) that alkalinize urine, causing precipitation of magnesium ammonium phosphate.

Question 5

A patient with nephrotic syndrome develops sudden flank pain and hematuria. CT shows right renal vein thrombosis. Which underlying condition most predisposes to renal vein thrombosis in nephrotic syndrome?

Accepted Answer

Membranous nephropathy

Answer

Membranous nephropathy has the highest risk of renal vein thrombosis among nephrotic syndromes due to urinary loss of anticoagulant proteins (antithrombin III, protein C/S).

Internal Medicine Exam Practice Test

Internal Medicine Exam Practice Test

Internal Medicine Exam Nephrology and Kidney Injury 3