The most common cause of Priapism in children is

Correct Answer: D

Rationale: Sickle cell disease tops pediatric priapism sickling blocks penile outflow (ischemic), prevalent in affected populations. Idiopathic is less defined residual category. Trauma causes high-flow rarer. Leukemia clogs vessels significant but less common. Sickle cell's dominance distinguishes it, key to pediatric etiology, unlike trauma or hematologic alternatives.

Correct Answer: A

Rationale: The nephron ends at the collecting duct, which drains into the renal papilla, unlike the distal convoluted tubule (preceding), glomerulus (start), or papilla (not part). This distinguishes the nephron's final segment, critical for urine concentration, contrasting with earlier structures.

Correct Answer: B

Rationale: GFR averages 180 L/day (125 mL/min × 1440 min), not 10 L, 1.5 L, or 1 mL/min (misunits). This quantifies filtration capacity, critical for renal function assessment, contrasting with incorrect scales.

Correct Answer: D

Rationale: Amino acid reabsorption in PCT uses active transport (Na+-linked), not albumin/creatinine (filtration) or water (osmosis). This distinguishes active mechanisms, critical for nutrient retention, contrasting with passive processes.

Correct Answer: A

Rationale: Renal papillae (pyramid tips) drain into minor calyces, not pelvis (later), ureter, or columns (cortex). This specifies urine origin, critical for medullary drainage, contrasting with later flow.