Chronic contained rupture of an abdominal aortic aneurysm mimicking a retroperitoneal mass with hydronephrosis.

Chronic contained rupture (CCR) of an abdominal aortic aneurysm rarely causes hydronephrosis and may mimic retroperitoneal malignancy. We report the case of a 66-year-old woman presenting with hydronephrosis caused by a CCR-related hematoma and an accessory renal artery originating from the terminal aorta. Biopsies excluded malignancy. Because endovascular repair carried a risk of type II endoleak and renal ischemia, open aneurysm repair with direct arterial reimplantation was performed. This approach relieved ureteral compression, achieved definitive aneurysm exclusion, and preserved renal perfusion. CCR should be considered in the differential diagnosis of irregular retroperitoneal masses associated with hydronephrosis.