Colonic melanosis (MC) is a rare non-inflammatory, benign, reversible lesion characterized by hyperpigmentation, which is mainly associated with the presence of lipofuscin-like substances in macrophages in the lamina propria of the colon. It is mainly thought to be related to the abuse of laxatives, especially anthraquinone laxatives, which have been reported in foreign literature. A. Etiology 1. Relationship with laxatives: Most studies at home and abroad believe that MC is related to long-term constipation and the use of laxatives, mainly anthraquinone laxatives: such as senna, rhubarb, boswellia bark, etc.. Other laxatives such as diphenylmethane (e.g., poo stop), fruit guide, aloe vera, magnesium sulfate, and marijuana capsules have also been reported to cause this disease. Li Jingxiang, Department of Anorectal Medicine, Dongzhimen Hospital, Beijing University of Traditional Chinese Medicine 2, related to apoptosis of colonic epithelial cells: It is believed that MC occurs due to various stimulating factors that damage the colonic epithelium, apoptotic cells and cell fragments are phagocytosed by macrophages in the lamina propria, and the residue after digestion forms lipofuscin-like substances in general, giving the intestinal mucosa a lipofuscin appearance, and it is found that the number of apoptotic epithelial cells and the degree of MC was found to be positively correlated with the degree of MC. However, there are different views that it is not related to the apoptosis of epithelial cells. Therefore, further research is needed. 3, some chronic inflammatory bowel disease and ulcerative colitis may be another factor leading to MC, and it has been reported that some patients with MC have no history of taking laxatives, the relationship of which needs further study. 4, related to constipation: MC patients without laxatives were also found to have melanosis, and the trend of colonic melanosis was reduced after normal bowel movements were treated, suggesting that constipation itself may be an important factor in causing MC. 5, other: such as chronic diarrhea, abdominal gunshot wounds after causing MC have been reported. The possible mechanism 1, the local stimulation of drugs: high dose of anthraquinones can increase the mucus secretion of intestinal glands, and make the intestinal epithelial cells produce more compatible get together, increase the activity of macrophages and chemotaxis, so that the phagocytosis of macrophages is enhanced, causing colonic nigrosis. 2, drug-induced apoptosis of intestinal epithelial cells: after entering the colon, various laxatives can cause transient, dose-related apoptosis of colonic mucosal epithelial cells, and the resulting apoptotic vesicles are engulfed by mononuclear macrophages and migrate to the lamina propria of the mucosa through small pores of the basement membrane. In the lysosomes of macrophages, apoptotic vesicles are converted into typical lipofuscin or other pigments, and with the long-term application of laxatives, these pigment-containing macrophages continue to accumulate and eventually develop into typical MC changes. 3. The drug itself contains resinous substances, which synthesize pigment granules in the large intestine and deposit in the lamina propria of mucosa, which are phagocytosed by monocytes and form black changes. The diagnosis is mainly based on the endoscopic and pathological examination results. Under endoscopy, the colonic mucosa is black, brown or dark gray, with yellow or pink edges or early lesions, tiger skin pattern, betel nut cut like or patchy; histological examination shows a large number of large mononuclear cells infiltrated with melanin and melanin deposits in the lamina propria, and other layers of the intestinal wall are normal. Most scholars believe that MC is a reversible lesion, and with the discontinuation of laxatives, the pigmented spots of MC can be weakened or even completely disappeared, therefore, the use of laxatives containing pigment is discontinued or not used, and other drugs such as oily laxatives, drugs to strengthen gastric power, laxative foods, etc. are used to treat constipation, eat more fiber-rich foods, and exercise appropriately. For those with chronic diarrhea, intestinal flora regulators can be used to reduce the incidence of MC and reverse the lesions already produced. Many scholars believe that colon cancer is not related to MC and laxatives, but some studies show that the incidence of colon polyps in MC is significantly higher than in other populations, and colon polyps are a clear precancerous lesion, so colonoscopy follow-up should be performed regularly for MC, and constipated patients should not use anthracycline laxatives as much as possible, and those who have them should stop using them. For those who have colon polyps, they should be removed promptly, and those who are diagnosed with colon cancer should be treated with surgery immediately.