Unilateral Multicystic Dysplastic Kidney in an Infant: A Case Report of Surgical Nephrectomy, Diagnostic Imaging, and Long-Term Outcomes.

Multicystic dysplastic kidney (MCDK) is a common congenital renal anomaly often considered benign when unilateral and managed conservatively. We report a female infant diagnosed antenatally with left-sided MCDK in the setting of maternal gestational diabetes mellitus (GDM). Postnatal imaging confirmed a nonfunctioning left kidney and a structurally normal right kidney with reduced glomerular filtration rate (GFR) of 49.7 mL/min/1.73 m². Laparoscopic nephrectomy at six months revealed complete parenchymal replacement by cysts with focal cartilaginous metaplasia. Over four years of follow-up, the right kidney demonstrated progressive hypertrophy, yet biochemical surveillance showed persistently reduced GFR (52 mL/min/1.73 m²), proteinuria (0.32 g/L), hyperphosphatemia (4.68 mg/dL), and elevated alkaline phosphatase (197 U/L). This case highlights the discordance between structural compensation and functional sufficiency in solitary kidney physiology, the potential influence of prenatal metabolic factors on nephrogenesis, and the importance of proactive biochemical surveillance. Early detection of proteinuria and phosphate retention, combined with timely nephroprotective interventions, may help mitigate the long-term risk of chronic kidney disease in children with congenital solitary kidneys.