MD Renal and Urinary Systems 3

Question 1

A 70-year-old man cannot empty his bladder and has a post-void residual of 350 mL. PSA is elevated. What is the most likely cause?

Accepted Answer

Benign prostatic hyperplasia

Answer

BPH causes bladder outlet obstruction in older men, leading to urinary retention and elevated post-void residual volumes.

Question 2

Renal tubular acidosis type IV is caused by which mechanism?

Accepted Answer

Hypoaldosteronism impairing K+ and H+ excretion

Answer

Type IV RTA results from aldosterone deficiency or resistance, impairing both K+ and H+ secretion in the collecting duct, causing hyperkalemia and a normal anion gap acidosis.

Question 3

A patient on lithium therapy develops polyuria and polydipsia. Water deprivation test shows urine does not concentrate even after desmopressin. What is the diagnosis?

Accepted Answer

Nephrogenic diabetes insipidus

Answer

Lithium causes nephrogenic DI by impairing collecting duct response to ADH; urine fails to concentrate despite exogenous desmopressin.

Question 4

Which finding on urinalysis is most consistent with acute tubular necrosis?

Accepted Answer

Muddy brown granular casts

Answer

ATN causes sloughing of tubular epithelial cells that form muddy brown granular casts, which are pathognomonic for this condition.

Question 5

A patient with HIV develops proteinuria and focal segmental glomerulosclerosis with collapsing variant. What is the most likely diagnosis?

Accepted Answer

HIV-associated nephropathy

Answer

HIV-associated nephropathy (HIVAN) classically presents with FSGS collapsing variant, heavy proteinuria, and rapid progression to ESRD in HIV-positive patients.

MD - Doctor of Medicine Practice Test

MD - Doctor of Medicine Practice Test

MD Renal and Urinary Systems 3