Internal Medicine Exam Nephrology and Kidney Injury 2

Question 1

A 58-year-old man with CKD stage 3b has a serum potassium of 6.2 mEq/L and ECG changes including peaked T-waves. Which intervention should be given FIRST?

Accepted Answer

IV calcium gluconate

Answer

IV calcium gluconate stabilizes the cardiac membrane and is the first-line treatment for hyperkalemia with ECG changes.

Question 2

A patient on long-term lithium therapy presents with polyuria (5 L/day) and dilute urine despite water deprivation. Urine osmolality fails to rise with exogenous ADH. What is the diagnosis?

Accepted Answer

Nephrogenic diabetes insipidus

Answer

Lithium causes nephrogenic diabetes insipidus by blocking ADH action on collecting duct V2 receptors, so exogenous ADH has no effect.

Question 3

A 72-year-old woman receives IV contrast for a CT scan. Her baseline creatinine is 1.8 mg/dL. Creatinine rises to 2.6 mg/dL at 48 hours. Which finding best distinguishes contrast-induced nephropathy from pre-renal azotemia?

Accepted Answer

Urine sodium > 40 mEq/L

Answer

A urine sodium >40 mEq/L indicates tubular dysfunction (FENa >1%), consistent with intrinsic AKI such as contrast nephropathy rather than pre-renal azotemia.

Question 4

A 35-year-old woman with SLE develops new proteinuria (3.5 g/day) and hematuria. Renal biopsy shows diffuse proliferative glomerulonephritis with subendothelial deposits. Which WHO/ISN class is this?

Accepted Answer

Class IV (diffuse proliferative)

Answer

Diffuse proliferative lupus nephritis with subendothelial deposits involving >50% of glomeruli is classified as ISN/RPS Class IV and carries the worst prognosis.

Question 5

A 45-year-old man with hypertension takes an ACE inhibitor. His serum creatinine rises from 1.0 to 2.1 mg/dL within one week of starting the drug. Renal artery duplex shows high-grade bilateral stenosis. What is the mechanism of AKI?

Accepted Answer

Loss of efferent arteriolar tone reducing GFR

Answer

ACE inhibitors block angiotensin II-mediated efferent arteriolar constriction; in bilateral renal artery stenosis this drops glomerular filtration pressure critically.

Internal Medicine Exam Practice Test

Internal Medicine Exam Practice Test

Internal Medicine Exam Nephrology and Kidney Injury 2