When childhood anomalies grow up: adult-onset discovery of multicystic dysplastic kidney, a case report

Multicystic dysplastic kidney (MCDK) is a congenital condition where noncommunicating cysts replace normal renal parenchyma, affecting about 1 in 4,300 live births. Unilateral MCDK is often asymptomatic, it may cause flank pain, hematuria, or hypertension. A 40-year-old male with history of hypertension since age 20 was referred to our clinic for evaluation of cystic kidney. He had no family history of kidney disease. His blood pressure was 145/85 mmHg. Serum creatinine was 0.8 mg/dL. Urinalysis did not show hematuria or proteinuria. Renal ultrasound showed an enlarged right kidney (15.4 cm) and smaller left kidney (9.8 cm) with lower pole cysts. Abdominal MRI confirmed numerous noncommunicating cysts with absent normal parenchyma in the left kidney, consistent with MCDK (Fig. 1). The right kidney and liver were normal. Genetic testing was negative for PKD1 and PKD2, and other less common variants of cystic kidney disease. The patient was managed conservatively with blood pressure control and monitoring of kidney function and proteinuria. MCDK is usually diagnosed by ultrasound or MRI. Asymptomatic unilateral cases are managed conservatively; nephrectomy is reserved for symptomatic or enlarging kidneys. Bilateral MCDK is typically fatal due to kidney failure and pulmonary hypoplasia. Unilateral cases have a good prognosis, with many undergoing spontaneous involution and compensatory hypertrophy of the contralateral kidney. Long-term follow-up includes monitoring for hypertension, malignancy, and proteinuria. Rarely, MCDK may mimic atypical autosomal dominant polycystic kidney disease. Early diagnosis and tailored care are key for favorable outcomes. Unilateral MCDK is rare but generally carries a good prognosis with conservative management and regular monitoring.