Darkening of the intestines may be caused by colonic melanosis, intestinal ischemic necrosis and other causes. 1. Colonic melanosis: It is a non-inflammatory bowel disease characterized by black pigmentation of the colonic mucosa, which may be related to patients’ long-term use of laxatives. Generally speaking, there are no specific signs and symptoms of colonic melanosis, which mainly manifests as abdominal distension and constipation, etc. The most typical manifestation is the discovery of different degrees and ranges of melanosis in the colon under enteroscopy. 2. Intestinal ischemic necrosis: If inguinal incarcerated hernia occurs, intestinal ischemia and necrosis may occur over a long period of time, which may lead to the blackening of the intestine. Intestinal ischemic necrosis can be manifested as sudden onset of severe colicky pain around the umbilicus or epigastric region, mostly accompanied by nausea, vomiting, diarrhea and frequent bowel movements, and other symptoms, and the condition is more serious. There are many other reasons why the intestines turn black, and it is recommended that the patient consult a doctor in time to clarify the cause of the disease under the guidance of a professional physician, so as not to delay the condition.