What is melanosis coli in adults with a history of constipation or gastrointestinal issues?

What is Melanosis Coli?

Melanosis coli is a benign condition characterized by brown or black pigmentation of the colonic mucosa caused by lipofuscin deposition within macrophages in the colonic lamina propria, most commonly associated with chronic use of anthraquinone-containing laxatives. 1

Pathophysiology and Etiology

• The pigmentation results from lipofuscin granules accumulating in macrophages within the colonic mucosa, creating the characteristic dark discoloration visible on endoscopy 2, 1
• Anthraquinone laxatives (such as senna/Cassia angustifolia) are the primary causative agents, with the apoptosis theory being the most widely recognized mechanism for melanosis coli development 1, 3
• The condition can develop from chronic use of herbal remedies like California herbal tea and other stimulant laxatives, not just pharmaceutical anthraquinone preparations 3, 4
• In patients with inflammatory bowel disease, melanosis coli may develop even without documented laxative use, suggesting chronic colitis itself could be a causative factor in approximately 80% of IBD patients with melanosis coli 5

Clinical Presentation and Diagnosis

• Melanosis coli is typically asymptomatic and discovered incidentally during colonoscopy or flexible sigmoidoscopy performed for other indications 1, 4
• The diagnosis is primarily made through endoscopic visualization showing brown to black pigmentation of the colonic mucosa, confirmed by histopathological examination demonstrating lipofuscin-laden macrophages 2, 1
• In chronic diarrhea investigations, melanosis coli is among the primary diagnoses identified on flexible sigmoidoscopy, alongside microscopic colitis, Crohn's disease, and ulcerative colitis 6
• Rarely, melanosis coli may present with white patches on colonoscopy rather than the typical dark pigmentation, requiring histological confirmation 4

Clinical Significance and Management

• This is a reversible, benign condition that does not require specific medical or surgical treatment unless serious malignancy is present 1
• The primary management approach involves discontinuing anthraquinone laxatives and modifying lifestyle habits that contribute to constipation 1
• Current evidence suggests a possible association between melanosis coli and colorectal adenomas, but not colorectal carcinomas, though the mechanisms remain incompletely understood 2
• Due to pharmaceutical side effects including electrolyte shifts and water loss, anthraquinone laxatives should not be used for long-term constipation management 2

Important Clinical Caveats

• In patients with prolonged herbal tea use (particularly California herbal tea) presenting with colonic pigmentation on colonoscopy, maintain high clinical suspicion for melanosis coli 3
• When evaluating chronic diarrhea in adults, screening for laxative abuse should be performed early in the investigation, as this becomes increasingly common in specialist referral practice 6
• In inflammatory bowel disease patients with melanosis coli, the mean disease duration is typically over 7 years, with most cases occurring in ulcerative colitis (72%) or Crohn's colitis (24%) 5