Spontaneous Rupture of a Renal Artery Branch Aneurysm in a Young Man: A Rare Case of Retroperitoneal Hemorrhage.

Renal artery aneurysms (RAAs) are rare vascular abnormalities, with branch aneurysms being even more uncommon. Spontaneous rupture of a branch RAA without prior trauma, infection, or known risk factors is extremely rare and can be life-threatening. We report a case of a previously healthy 22-year-old male patient who presented with sudden left flank pain and hematuria. Initial imaging revealed a large retroperitoneal hematoma; however, the source of bleeding was not immediately apparent. Following conservative management, a delayed contrast-enhanced CT and angiography identified a ruptured left renal artery branch aneurysm. The patient was successfully treated with coil embolization and recovered uneventfully. This case highlights the importance of considering RAA rupture in young patients with spontaneous retroperitoneal hemorrhage, supports the role of conservative management with close observation, and the role of angiographic embolization in cases of unclear bleeding sources.