Infantile Homocystinuric Urolithiasis With Staghorn Calculus: A Case Report of Nephron-Sparing Surgical Salvage in an Intraparenchymal Renal Pelvis.

Pediatric urolithiasis, though uncommon, carries significant morbidity when driven by underlying metabolic disorders. Classical homocystinuria, caused by cystathionine beta-synthase (CBS) deficiency, is a rare autosomal recessive inborn error of sulfur amino acid metabolism. While ectopia lentis, skeletal anomalies, and thromboembolic events define its classical triad, urolithiasis presenting within the first year of life remains exceptionally rare in surgical literature. A one-year-old male, born to consanguineous parents with known homocystinuria, presented with gravel-like urinary deposits since five months and progressive dysuria since six months. Ultrasonography revealed a 10 mm right renal calculus, a 23 mm vesical calculus, and features of chronic cystitis. He underwent cystolithoscopy, open cystolitholapaxy, and double-J (DJ) stenting. Repeat imaging at two months revealed a 17 mm right staghorn calculus with mild hydronephroureterosis. Intraoperatively, an intraparenchymal pelvis was encountered with the staghorn calculus densely adherent to the indwelling stent, precluding conventional retrieval. Nephrectomy was deferred in favour of nephron-sparing surgery. The calculus was extracted en bloc, a fresh DJ stent inserted, and watertight ureteral re-anastomosis performed. Homocystinuria can drive aggressive multi-level urolithiasis in infancy. Open pyelolithotomy with ureteral re-anastomosis remains a viable nephron-saving strategy when minimally invasive approaches are anatomically unfeasible. Sustained metabolic-surgical multidisciplinary management is essential for long-term renal preservation.