A 91 year old man presented with acute onset right sided abdominal pain that radiated to his right groin. He reported having had an urge to urinate and had subsequently collapsed on his way to the toilet. He had no back pain or incontinence of urine or faeces. His medical history included controlled hypertension, but he was otherwise fit and well and living independently.

On examination, the patient had a normal temperature but was tachycardic, with a pulse rate of 110 beats/min. His blood pressure was 85/50 mm Hg, which improved to 110/70 mm Hg after fluid resuscitation with 2 l of crystalloid solution. His chest was clear. Examination of his abdomen revealed a tender and non-pulsatile 15×10 cm mass in the right iliac fossa that extended to the groin. There were strong femoral pulses bilaterally.

Chest radiograph did not show any evidence of free intraperitoneal air, suggestive of perforation. Blood tests showed a normal white blood cell count and a haemoglobin level of 9.1 g/dl. Urea, creatinine, electrolytes, and amylase concentrations were all in the normal range. An urgent computed tomogram with intravenous contrast was performed on the abdomen and pelvis (figs 1 and 2).⇓ ⇓