Melanosis coli: Harmless pigmentation? A case-control retrospective study of 657 cases

Abstract

Backgrounds and aimsThe association of melanosis coli with the development of colorectal polyps remains uncertain.MethodsFrom a total of 18263 patients who had received colonoscopy in our hospital, 219 with melanosis coli cases and 438 controls matched by age and sex (at 1:2 ratio) were included in this study. The association of incidence, number, location, and pathology of colorectal neoplasm with grades and distribution of melanosis coli were analyzed.ResultsMelanosis coli was associated with significantly more colorectal polyps than control, a higher incidence of numerous colorectal polyps (number ≥ 20) (7.3% vs 0.5%; p < 0.001), and higher number of small colorectal polyps (diameter ≤ 5 mm; p < 0.01). Patients with melanosis coli had higher incidences of low-grade adenomas (31.1% vs 23.3%, p < 0.05) and non-adenoma polyps (20.1% vs 12.8%, p < 0.05) than the controls. On multivariate analysis, melanosis coli was independently associated with increased detecting rates of low grade adenoma (OR = 1.54; 95%: 1.06–2.23; p < .05), non-adenoma polyp (OR = 1.72; 95%: 1.11–2.70; p < .05) and numerous polyps (OR = 16.2, 95%: 3.66–71.6; p < .05). There was no significant difference in the incidence of high-grade adenomas or adenocarcinomas in the two population groups, but the numbers of these lesions were insufficient to permit firm conclusions. No significant differences in incidence, number, and pathology of colorectal polyps between individuals with melanosis coli of three different grades of severity were found. Melanosis located predominantly in the right colon had an interestingly lower incidence of colonic polyps in right colon than did melanosis located predominantly in the left colon or total colon (8.9% vs. 26.3%, 24.0%, p < 0.05). Patients with melanosis coli had significantly more nonspecific distal ileal ulcers than did controls (8.0% vs 0%, p < 0.001).ConclusionMelanosis coli is associated with a higher incidence and number of colonic non-adenoma polyps and low-grade adenomas, and higher incidence of distal ileal ulcers. Melanosis coli may not be a harmless pigmentation, but a sign of chronic injury of colonic and intestinal mucosa.

Melanosis Coli: Case Report

“…10 In a study that reported the association with non-neoplastic polyps that contain pigment, the toxic effect resulting in the destruction of the apoptotic colonic epithelial cells was claimed to cause the development of the colorectal polyps, as well as melanosis coli. 8 Although no polyp was detected in our case, it was observed that there was no macroscopic and microscopic pigment accumulation in ulcerated tumor tissue in accordance with the literature. Diffuse black-brown pigment was observed on the mucosa and serosal surface of the tumor proximal.…”

“…7 It can be seen in varying rates in inflammatory bowel disease, colonic diverticulum, chronic diarrhea, nonsteroidal anti-inflammatory drug use, colorectal polyps and tumors. 5,8 It has been reported in the literature that it is frequently associated with colonic polyps. 5,9 In one study, it was emphasized that pigment-free polyps were more easily detected in endoscopic examination because of the black-brown color of the mucosa.…”

Melanosis of The Appendix Presenting with the Clinic of Acute Appendicitis

“…1,2 Although it is frequently located in the colonic mucosa, especially in the the cecum part, MC can be seen in the small intestine as well. 3 However, it may be seen in patients with chronic diarrhea, inflammatory bowel disease, and chronic use of non-steroidal anti-inflammatory drugs. 3,4,5 Improper laxative use due to chronic constipation may cause MC, which is more common in elder patients.…”

“…3 However, it may be seen in patients with chronic diarrhea, inflammatory bowel disease, and chronic use of non-steroidal anti-inflammatory drugs. 3,4,5 Improper laxative use due to chronic constipation may cause MC, which is more common in elder patients. 1,2 Acute appendicitis is one of the most common causes of abdominal pain in patients admitted to the emergency department.…”

“…1,2 MC often affects the cecum; the rectum is mostly affected secondary to the chronic use of anthraquinone-containing laxatives. 2,3 MC was first described by Cruveilhier in 1829, and named MC by Virchow in 1857. 1,2…”