A rare case of ulcerative colitis relapse in a diverted colon after rectal cancer surgery: efficacy of carotegrast methyl.

This case presents a rare instance of ulcerative colitis (UC) relapse in the functionally isolated left colon following surgery for rectal cancer associated with UC. A 62-year-old man, suspected of having cancer based on positron emission tomography (PET)-computed tomography (CT) findings and elevated carcinoembryonic antigen levels, underwent robot-assisted low anterior resection and temporary transverse colostomy. Postoperatively, leakage and infection made it difficult to administer conventional local treatments or corticosteroids; however, remission was achieved with the oral α4-integrin inhibitor, carotegrast methyl, allowing for stoma closure. To our knowledge, this report is the first to describe the use of carotegrast methyl for recurrent UC in a diverted colon. This case demonstrates that carotegrast methyl may serve as an effective steroid-sparing option for UC relapse in complex postoperative anatomical contexts. It also highlights the potential utility of PET-CT as an adjunctive diagnostic tool for UC-associated cancer.