The major pathophysiological mechanisms that contribute to Uric Acid stones are all EXCEPT

Correct Answer: D

Rationale: Uric acid stones form due to low urinary volume (concentrates urate), low pH (undissociated uric acid), and hyperuricosuria (excess urate excretion) direct urinary factors. Hyperuricemia (high blood urate) contributes indirectly via excretion but isn't a primary urinary mechanism stones need urinary conditions, not just serum levels. Low volume reduces dilution, low pH shifts solubility, and hyperuricosuria overloads urine. Exclusion of hyperuricemia distinguishes it, critical for focusing on urine-based stone formation, unlike blood-centric error.

Correct Answer: B

Rationale: Recurrent ischemic priapism ties to PDEâ‚… dysregulation impaired cGMP breakdown prolongs erections, trapping blood. Adenosine underproduction is theoretical, not primary less evidence. Rho-kinase increase stiffens vessels, not priapism's core. Reduced relaxation follows dysregulation, not cause secondary. PDEâ‚…'s role distinguishes it, critical for ischemic priapism's molecular basis, unlike speculative, unrelated, or resultant mechanisms.

Correct Answer: A

Rationale: 99Tc-MAG3 excels in renal insufficiency and obstruction high extraction, shows function and drainage despite low GFR. DTPA relies on filtration less effective in insufficiency. DMSA assesses cortex, not obstruction static. EC is similar but less common MAG3 preferred. MAG3's dynamic imaging distinguishes it, key for compromised kidneys, unlike filtration or static options.

Correct Answer: B

Rationale: VVF from obstructed labor is the most common etiology in developing countries prolonged pressure necroses bladder/vagina. Apex location fits surgical causes, not labor less typical. Multiparity increases risk but isn't defining primips too. Large, complex fistulas are usual repair challenging. Prevalence in developing regions distinguishes it, key to obstetric fistula burden, unlike site, parity, or size errors.

Correct Answer: B

Rationale: Vesicoureteral reflux (VUR) alters compliance measurement urine backflow reduces true bladder pressure readings, skewing accuracy. Radiation stiffens bladder lowers compliance, false reading. Obstruction raises pressure overestimates. Tuberculosis scars bladder reduces elasticity, inaccurate. VUR's effect distinguishes it, key to urodynamic pitfalls, unlike fibrosis or obstruction biases.