Incidental finding of a complex right fused supernumerary kidney with vascular and ureteral anomalies following abdominal trauma: A case report.

Fused supernumerary kidney (fused SNK) is an extremely rare congenital malformation of the urinary system. This article reports a 59-year-old male patient who was admitted to the emergency department because of severe right flank pain and gross hematuria 4 days after a fall. Computed tomography angiography (CTA) revealed a complex combination of variations: the absence of the left kidney and left renal vessels and 3 partially fused supernumerary kidneys (upper pole, middle, and lower pole units) in the right renal fossa with 3 independent collection systems. The vascular and ureteral anatomy was highly anomalous, and an incidental congenital arteriovenous fistula (AVF) directly communicating with the inferior vena cava was identified in the upper pole kidney. Imaging confirmed an AAST Grade IV laceration in the lower pole kidney with active contrast extravasation and a large perirenal hematoma. The patient underwent emergency superselective transcatheter arterial embolization (TAE) using N-butyl cyanoacrylate (NBCA). In accordance with the "damage control" principle in the context of hemorrhagic shock, only active hemorrhage was treated, while asymptomatic AVF was left for conservative surveillance. Follow-up at 6 months revealed stable renal function. This case emphasizes the critical role of multiphase CTA in mapping complex anomalies and demonstrates that TAE is a safe, parenchyma-preserving intervention, for managing trauma in patients with rare renal malformations.