Differential diagnosis of urinary retention: aneurysm of the iliac artery

A 69-year old male presented with anuric acute renal failure. Abdominal ultrasound at admission revealed a mass in the pelvis thought to be the urinary bladder and the diagnosis of urinary retention was made. When placement of an urinary catheter did not induce urine flow, digital rectal examination was done. Palpation of a pulsating mass finally led to the diagnosis of aneurysm of the iliac artery. Based on this case, the general problem of diagnosing an iliac artery aneurysm is discussed.