A rare cause of abdominal pain

A 28 year old injecting drug user presented to the hospital with non-specific symptoms of abdominal pain and fever. Clinical examination showed diffuse abdominal tenderness, most prominent in the left upper quadrant, with localised guarding and rigidity. One month earlier he had presented with a septic iliofemoral vein thrombosis and was started on warfarin. A portable chest radiograph was limited but unremarkable and did not show subphrenic air. Blood tests showed anaemia, consistent with his previous admission, and raised inflammatory markers of white blood cell count 19.88×10⁹/l and C reactive protein 77 mg/l. He underwent computed tomography of the abdomen (fig 1⇓).