A Case with a Pathological Course Resembling Ulcerative Colitis after Rectal Cancer Surgery with Diversion

The development of de novo ulcerative colitis (UC) is rare after colorectal cancer surgery. In contrast, diversion colitis is a common inflammatory condition of the defunctionalized colon following stoma creation, often complicating postoperative diagnosis.

A 49-year-old man with advanced rectal cancer was treated with neoadjuvant chemotherapy followed by robot-assisted ultra-low anterior resection with diverting stoma. His postoperative course was complicated by an anastomotic leak. During the diversion period, he developed fever, diarrhea, and colonic inflammation that was initially diagnosed as diversion colitis and responded dramatically to systemic steroid therapy. Following stoma closure, recurrent anastomotic ulceration and diffuse colitis developed, again showing marked steroid responsiveness. Based on the overall clinical course, the patient was considered to have a clinical course resembling UC rather than diversion colitis. The patient achieved sustained remission with systemic steroids and mesalamine, with no recurrence of intestinal inflammation or cancer.

This case underscores the challenges in distinguishing UC from diversion colitis in the postoperative setting. Recurrent anastomotic inflammation with pronounced steroid responsiveness should prompt consideration of underlying UC, even after colorectal cancer surgery.