A 66 year old white female comes to your office with evidence of a fecal impaction which you successfully treat. She relates a history of chronic laxative use for most of her adult years. After proper preparation, you
perform sigmoidoscopy and note that the anal and rectal mucosa contain scattered areas of bluish-black discoloration. Which one of the following is the most likely explanation for the sigmoidoscopic findings‟
- a) Endometriosis
- b) Collagenous colitis
- c) Melanosis coli
- d) Metastatic malignant melanoma
- e) Arteriovenous malformations
0 voters
The correct answer is C
Explanation by Shahriar’s AMC guideline
This patient has typical findings of melanosis coli, the term used to describe black or brown discoloration of the mucosa of the colon. It results from the presence of dark pigment in large mononuclear cells or
macrophages in the lamina propria of the mucosa. The coloration is usually most intense just inside the anal sphincter and is lighter higher up in the sigmoid colon. The condition is thought to result from
fecal stasis and the use of anthracene cathartics such as cascara sagrada, senna, and danthron. Ectopic endometrial tissue (endometriosis)
most commonly involves the serosal layer of those parts of the bowel adjacent to the uterus and fallopian tubes, particularly the rectosigmoid colon. Collagenous colitis does not cause mucosal pigmentary changes. Melanoma rarely metastasizes multicentrically to the
bowel wall. Multiple arteriovenous malformations are more common in the proximal bowel, and would not appear as described. regards Dr.shahriar ahmed