Beckwith-Wiedemann syndrome and medullary sponge kidney: a case report of two rare but related entities.

BACKGROUND: Beckwith-Wiedemann syndrome (BWS) is a congenital overgrowth disorder that may be associated with renal abnormalities, although benign renal manifestations presenting in adulthood are less well characterized. CASE DESCRIPTION: We report the case of a 20-year-old woman with genetically confirmed BWS who was diagnosed with medullary sponge kidney (MSK) during adulthood after imaging evaluation for suspected renal abnormalities. Contrast-enhanced computed tomography and intravenous urography demonstrated characteristic medullary collecting duct dilatation with nephrocalcinosis, consistent with MSK, associated with hypercalciuria and hypocitraturia. Medical management with thiazide diuretics and potassium citrate achieved metabolic control and stable imaging findings. CONCLUSION: This case highlights the importance of considering MSK in patients with BWS and underscores the role of appropriate imaging and metabolic evaluation for accurate diagnosis and long-term management.