大腸鏡是目前大腸癌篩檢及大腸疾病的主要檢查工具，但嚴重的併發症在例行性大腸鏡檢查後是非常罕見的。在這裡我們描述一位 64 歲的女性，過去曾經接受過子宮切除術和心臟瓣膜置換，且目前正在接受抗凝血劑治療。在接受大腸鏡檢查術後，發生嚴重的腹痛及休克跡象。腹部電腦斷層顯示大量腹水，緊急剖腹探查發現結腸漿膜撕裂出血。漿膜撕裂出血是非常少見的大腸鏡併發症。我們討論這一難得見併發症的可能機轉，希望往後在高風險病人中能夠事先預期結腸漿膜撕裂出血的可能，並及早介入預防。

Colonoscopy is now the standard for colorectal cancer screening and study of colon diseases. Serious complications are rare in routine colonoscopies without a biopsy or polypectomy. We report a case of a 64-year-old woman with a history of a hysterectomy and heart valve replacement under warfarin therapy, who underwent colonoscopy because of rectal bleeding. Severe persisting abdominal pain and signs of shock were found after the procedure. An abdominal computed tomographic scan showed ascites. An emergency laparotomy was performed and revealed a serosal tear at the sigmoid colon with hemoperitoneum. A bleeding serosal tear is a rarely reported complication of colonoscopy. The risk of a bleeding serosal tear should be considered when performing a colonoscopy especially in high-risk patients with prior abdominal surgery and concurrent use of anticoagulants.