Fused Supernumerary Kidney with Single Pelvis and Ureter; Presenting with Stones: A Case Report and Literature Review

INTRODUCTION: A supernumerary kidney is an extremely rare congenital anomaly, defined as the presence of one or more extra kidneys. Thus far, there have been less than 100 cases reported in the medical literature. It has its capsule, vascular supply, and collecting system. It frequently causes diagnostic challenges in clinical practice. The supernumerary kidney can be symptomatic due to the presence of stone. CASE PRESENTATION: We present a case of a 19-year-old male patient who came to our clinic with the complaint of abdominal pain. On computed tomography urography (CTU), he was found to have a caudally located left fused supernumerary kidney with a separate vascular supply. Both left kidneys had a separately draining calyceal systems uniting at the left renal pelvis and drained by a single ureter. Multiple left renal stones (largest measures 4cm x 2.2cm) in both kidneys were also seen. The stones were removed surgically by doing pyelolithotomy and radial nephrolithotomy. The patient was doing well during follow-up visits with the improvement of abdominal pain. CONCLUSION: Supernumerary kidney is a very rare congenital renal anomaly. This case is even unique, because of the fused supernumerary kidney and the presence of a single left renal pelvis and ureter. Imaging is very essential for planning surgical intervention. Stones in such kidneys can be managed with nephrolithotomy and/or pyelolithotomy.