Radiology for the surgeon: Soft-tissue case 60.

A 58-year-old man complained of having had pain for the past 12 hours in his left-lower quadrant, with nausea and vomiting. His pain was well localized and without radiation. He had not had a bowel movement since the onset of the pain. He had had no previous similar episodes, and had no other significant past medical or surgical history. Upon examination, he was focally tender in the left lower quadrant, with a tender mass palpable about halfway from the umbilicus to the anterior superior iliac spine. Bowel sounds were absent; the remainder of the examination was noncontributory. His white blood cell count was elevated at 12 800 × 106/L. A preoperative diagnosis of diverticulitis was entertained and a CT image of the abdomen requested (Fig. 1). What is the diagnosis?