本文报告1例胸腺鳞癌Ⅳ期患者，末次化疗在接受白蛋白紫杉醇、卡铂联合替雷利珠单抗治疗后5.5周，全结肠黏膜出现散在充血糜烂及浅溃疡，CT显示结肠壁显著增厚和水肿。后自肛门排出一段约20 cm的坏死肠黏膜组织，活检病理显示为免疫相关性肠炎，CTCAE 3级。经对症保守治疗后疗效欠佳。后经多学科会诊后将坏死段肠黏膜组织切除。患者术后恢复顺利，病理显示肠黏膜缺血性坏死伴有重度炎症反应。本病例展示了免疫检查点抑制剂相关性结肠炎临床表现及诊治的复杂性及多样性，据此，笔者建议对出现便血或腹泻的患者进行早期评估，积极开展多学科会诊，必要时及时外科干预，避免严重不良后果的发生。

A case of severe immune-related colitis complicated by spontaneous transanal passage of necrotic intestinal mucosa following immune checkpoint inhibitor therapy is reported. The patient was diagnosed with stage IV thymic squamous cell carcinoma and was treated with albumin-bound paclitaxel and carboplatin in combination with tislelizumab. At 5.5 weeks after the last cycle of combined chemotherapy and immunotherapy, colonoscopy revealed scattered mucosal congestion, erosions, and superficial ulcers throughout the colorectum. Subsequently, an approximately 20-cm-long segment of dark-red necrotic intestinal mucosa was discharged through the anus. Histopathological examination of intestinal mucosal biopsy specimens supported the diagnosis of immune-related enterocolitis, which was classified as grade 3 according to the Common Terminology Criteria for Adverse Events. Conservative treatment, including bowel rest, nutritional support, mucosal protection, and symptomatic management, resulted in no significant clinical improvement. Following multidisciplinary consultation involving the departments of gastroenterology, colorectal surgery, and oncology, the necrotic intestinal tissue was surgically removed. The patient recovered uneventfully after the procedure. Histopathological examination of the resected tissue demonstrated ischemic necrosis of the intestinal mucosa accompanied by a severe inflammatory response. This case highlights the complexity and diversity of the clinical manifestations, diagnosis, and management of immune checkpoint inhibitor–related colitis. For patients receiving immune checkpoint inhibitors who develop hematochezia or diarrhea, early assessment and grading of colitis, repeated clinical evaluation, and prompt multidisciplinary consultation are recommended. When necrotic tissue is identified or conservative treatment is ineffective, timely surgical intervention should be considered to prevent serious adverse outcomes.