Melanosis coli refers to the obvious brown or black coloration of the colorectal mucosa. The main causes of the disease are as follows: 1. Intestinal dysfunction, mainly referring to chronic constipation. 2. Long-term intake of anthraquinone laxatives, such as senna, aloe, and rhubarb. Since chronic constipation and laxatives are closely related, long-term abuse of anthraquinone laxatives can lead to the occurrence of melanosis coli. The occurrence of melanosis coli has no relation to gender but is closely related to age. As age increases, the detection rate shows an upward trend. The pigmentation of the colorectal mucosa in melanosis coli can be severe, but the condition itself does not produce related symptoms. The symptoms shown by patients are often associated with accompanying diseases, such as intractable constipation and colorectal cancer. It often presents as a group of symptoms related to constipation, such as abdominal pain, abdominal distension, and difficulty in defecation. Barium enema may show the disappearance of colonic haustra, elongation of the transverse colon or sigmoid colon, etc. Electronic colonoscopy reveals that the colorectal mucosa has a dark-brown change.