## Correct Answer: C. Autosomal dominant polycystic kidney disease Autosomal dominant polycystic kidney disease (ADPKD) is the most likely diagnosis based on the clinical presentation and imaging findings. The key discriminating features are: (1) **bilateral renal cysts** on ultrasound, (2) **early-onset hypertension** (age 40), (3) **hematuria and loin pain** from cyst rupture or stone formation, and (4) **positive family history** (brother died of stroke at age 40, suggesting cerebral aneurysm rupture—a known extrarenal manifestation of ADPKD). ADPKD is caused by mutations in PKD1 (chromosome 16) or PKD2 (chromosome 4) genes and accounts for ~10% of end-stage renal disease in India. The disease presents with progressive bilateral cyst formation, leading to hypertension in 50–70% of patients by age 40. Hematuria occurs in 50% of patients due to cyst hemorrhage or associated nephrolithiasis. The family history of early stroke is classic for ADPKD-associated cerebral aneurysms (berry aneurysms in 8–10% of ADPKD patients), which rupture and cause subarachnoid hemorrhage. The ultrasound findings of multiple bilateral cysts in a hypertensive patient with hematuria and strong family history of early vascular death make ADPKD the definitive diagnosis. Management includes ACE inhibitors/ARBs for hypertension control, screening for cerebral aneurysms (MRA), and monitoring renal function. ## Why the other options are wrong **A. Renal cell carcinoma** — RCC typically presents with unilateral renal mass, not bilateral multiple cysts. While hematuria and loin pain occur in RCC, the imaging shows diffuse bilateral cystic changes rather than a solid enhancing mass. RCC does not explain the family history of early stroke or the bilateral symmetric involvement. The presence of hypertension predating hematuria also favors ADPKD over malignancy. **B. Autosomal recessive polycystic kidney disease** — ARPKD presents in infancy or early childhood with bilateral renal enlargement and hepatic fibrosis. A 40-year-old man with hypertension and hematuria would have already progressed to end-stage renal disease if he had ARPKD; survival to age 40 is rare without transplantation. ARPKD lacks the family history pattern of early vascular death seen here. ADPKD's later presentation and adult-onset hypertension fit this case far better. **D. Tuberculosis of the kidney** — Renal TB presents with unilateral involvement, cavitary lesions, and 'moth-eaten' calyces on imaging—not bilateral cysts. TB typically causes sterile pyuria, constitutional symptoms, and a history of pulmonary TB or contact. The bilateral symmetric cystic pattern, family history of stroke, and hypertension are incompatible with TB. Ultrasound findings in TB show destruction and scarring, not cyst formation. ## High-Yield Facts - **ADPKD prevalence**: 1 in 400–1000 live births; accounts for ~10% of ESRD in India. - **Hypertension in ADPKD**: Present in 50–70% by age 40; due to renin-angiotensin activation and cyst compression. - **Cerebral aneurysms**: Found in 8–10% of ADPKD patients; berry aneurysms rupture causing subarachnoid hemorrhage—leading cause of death in young ADPKD patients. - **Hematuria mechanism**: Cyst rupture into collecting system or associated nephrolithiasis (25–30% of ADPKD patients). - **Ultrasound criteria for ADPKD**: Bilateral renal cysts (≥2 cysts in each kidney if age <30; ≥2 cysts in one kidney if age 30–59; ≥4 cysts in each kidney if age ≥60). - **First-line therapy**: ACE inhibitors or ARBs for hypertension; tolvaptan (vasopressin antagonist) slows cyst growth in select cases. ## Mnemonics **ADPKD Triad** **Bilateral Cysts** + **Early Hypertension** + **Cerebral Aneurysm** = ADPKD. Remember: 'A' for Autosomal, 'D' for Dominant, 'PKD' for Polycystic Kidney Disease. When you see a young hypertensive with bilateral cysts and family history of stroke, think ADPKD first. **ADPKD vs ARPKD Age Rule** **ADPKD = Adult** (presents age 30–50), **ARPKD = Adolescent/Antenatal** (presents in infancy/childhood). A 40-year-old with cysts = ADPKD until proven otherwise. ## NBE Trap NBE may pair "bilateral cysts" with ARPKD to trap students who memorize "bilateral = recessive" without considering age of presentation. ADPKD is far more common in adults; ARPKD is a pediatric disease. The family history of early stroke is the key differentiator—unique to ADPKD's cerebral aneurysm association. ## Clinical Pearl In Indian clinical practice, ADPKD is often diagnosed late (at CKD stage 3–4) because patients present with hypertension or hematuria and imaging is not pursued until complications arise. Screening first-degree relatives with renal ultrasound and MRA for cerebral aneurysms is critical—many young ADPKD patients in India die of preventable subarachnoid hemorrhage before renal replacement therapy becomes necessary. _Reference: Robbins Ch. 20 (Kidney); Harrison Ch. 279 (Polycystic Kidney Disease); Bailey & Love Ch. 76 (Urological Surgery)_
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