Successful treatment of noninfectious hemorrhagic cystitis with intravesical hyaluronic acid in a 5-year-old boy: a case report.

Hemorrhagic cystitis (HC) in children is most associated with infection or treatment-related toxicity, whereas other cases remain uncommon. We report a 5-year-old boy presenting with recurrent painless gross hematuria in whom a structured, stepwise evaluation excluded glomerular, infectious, structural, and systemic causes. Cystoscopy revealed diffuse mucosal inflammation with focal hemorrhagic changes involving the bladder neck and posterior wall, consistent with noninfectious HC. In the absence of an identifiable etiology and with persistent symptoms, management was directed toward restoring urothelial barrier integrity using intravesical hyaluronic acid (HA). The clinical response was rapid, with resolution of gross hematuria after the first instillation, followed by sustained remission and progressive endoscopic improvement. The treatment was well tolerated, and the patient remained disease-free at 12 months of follow-up. This case highlights the diagnostic complexity of unexplained hematuria in children and supports a potential role of urothelial barrier dysfunction in the pathogenesis of noninfectious HC.