A Case of Left Duplex Kidney with Hydronephrosis Mimicking a Left Renal Cyst in a 29-Year-Old Woman

BACKGROUND Duplex kidney, also known as duplex renal collecting system, consists of 2 ureters arising from a single kidney and is a common congenital anomaly. The condition is usually an asymptomatic normal variant. However, abnormal anatomic variants such as hydronephrosis, vesicoureteral reflux (VUR), and ureterocele are sometimes observed in a patient with a duplicated kidney. These abnormal variants usually lead to diagnostic challenges. Here, we report a case of congenital left duplex kidney with hydronephrosis that presented as an isolated left renal cyst in a 29-year-old woman. CASE REPORT We present the case of a 29-year-old woman who had left-side abdominal pain and fever for 1 day. Left-side flank throbbing pain was also noted. Laboratory investigations showed leukocytosis, pyuria and bacteriuria. Renal ultrasound revealed a huge hypoechoic mass around the left kidney, which was suspected to be a huge renal cyst or renal abscess. Under the impression of acute pyelonephritis with abscess formation, the patient was admitted for antibiotic treatment. The following abdominal computed tomography (CT) revealed a left duplex kidney with severe hydronephrosis and hydroureter. A percutaneous nephrostomy was then performed. Next, following a discussion with the patient, she underwent a robot-assisted left heminephrectomy. CONCLUSIONS A duplex kidney and collecting system should be considered when chronic urologic problems occur. This report shows that because duplex kidney is a relatively common congenital abnormality, it should be considered in the differential diagnosis in young patients who present with renal cyst. This case also shows that patients can be managed effectively using robot-assisted heminephrectomy.