Fig. 3

Colonoscopy performed on day 40, 75. Colonoscopy performed on day 40 (a–c) and day 75 (d–f) after admission. The colon is edematous throughout, with scattered erythema and erosions (a). The sigmoid colon has particularly strong inflammatory changes, with scattered longitudinal ulcers. Slight improvement from the previous colonoscopy (b, c). A circumferential ulcer and stricture are noted 2 cm from the antral dentate line (f). Beyond the stricture is a fairly wide lumen with necrotic material in the mucosa or rectal wall (d, e). Perforation of the retroperitoneum was a highly suspicious finding. On its mouth side, a circumferential ulceration continued