This article discusses two cases of melanosis coli, a benign condition resulting from chronic laxative use. It highlights the importance of proper diagnosis and management to differentiate it from colorectal neoplasms and promote healthier alternatives for constipation relief.

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Case report 1

Melanosis coli associated with chronic laxative abuse

Patient information

• Age: 55
• Gender: Female
• Medical history: Hypertension, irritable bowel syndrome
• Chief complaint: Chronic constipation and abdominal discomfort
• Duration of symptoms: 3 years

Summary

 A 55-year-old female presented with a history of chronic constipation and abdominal discomfort for the past 3 years. She reported using over-the-counter laxatives excessively during this period in an attempt to alleviate her constipation.

Diagnosis

1. Physical examination revealed mild tenderness in the lower abdomen and a history of irregular bowel movements.
2. A colonoscopy was performed, showing extensive brown pigmentation of the colonic mucosa, consistent with melanosis coli.
3. Biopsy samples confirmed the presence of pigment-laden macrophages within the lamina propria.
4. The patient was counselled on the potential complications of chronic laxative abuse and advised on alternative methods for managing constipation.

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Case report 2

Melanosis coli mimicking colorectal neoplasm

Patient information

• Age: 70
• Gender: Male
• Medical history: Diabetes mellitus, coronary artery disease
• Chief complaint: Change in bowel habits, weight loss
• Duration of symptoms: 6 months

Summary

A 70-year-old male presented with a 6-month history of change in bowel habits, including alternating constipation and diarrhoea, along with unintentional weight loss. His medical history included diabetes mellitus and coronary artery disease.

Diagnosis

1. Physical examination was unremarkable, and laboratory tests were within normal limits.
2. A colonoscopy revealed a dark, velvety appearance of the colonic mucosa predominantly in the rectum and sigmoid colon, raising suspicion for malignancy.
3. Multiple biopsies were obtained, and histopathological examination revealed melanosis coli characterised by intracellular pigment accumulation within macrophages.
4. The patient's laxative use history was explored, and it was discovered that he had been taking aloe-containing herbal laxatives for several years.

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Melanosis coli

1. This discolouration results from the accumulation of pigment-laden macrophages within the lamina propria, the connective tissue layer beneath the epithelial cells lining the colon.
2. While melanosis coli itself is generally not associated with serious health risks, it often raises concern due to its potential to mimic other colonic pathologies, such as colorectal neoplasms.

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Causes

1. The primary cause of melanosis coli is the chronic use of certain types of laxatives, particularly those containing anthraquinones, which are natural compounds found in certain plants.
2. These laxatives, often used for prolonged periods to treat constipation, disrupt the normal processes of colonic mucosal cells, leading to the accumulation of pigment within macrophages.
3. As a result, the colonic mucosa appears darkened and velvety in appearance.

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Clinical presentation

1. Patients with melanosis coli may be asymptomatic or present with non-specific gastrointestinal complaints, such as altered bowel habits, abdominal discomfort, or bloating.
2. Occasionally, patients may report a history of chronic laxative use, which can provide a valuable clue for diagnosis.

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Diagnosis

1. The definitive diagnosis of melanosis coli is made through endoscopic examination, typically during colonoscopy.
2. The colonic mucosa will display characteristic brown to black pigmentation, often most pronounced in the rectum and sigmoid colon.
3. Biopsy samples taken from the affected mucosa will reveal the presence of pigment-laden macrophages within the lamina propria.

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Differential diagnosis

1. Melanosis coli can resemble other more severe conditions, such as colorectal neoplasms, due to the visual similarity of the darkened mucosa.
2. Therefore, it is crucial to differentiate melanosis coli from malignant or pre-malignant lesions through histopathological examination.

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Management

1. Melanosis coli is generally a benign condition that does not require specific treatment.
2. The most important step is addressing the underlying cause, which often involves discontinuing the use of laxatives containing anthraquinones.
3. Patients should be educated about the potential risks of chronic laxative use and encouraged to adopt healthier dietary and lifestyle habits to manage constipation.
4. Regular follow-up with a healthcare provider may be recommended to monitor the resolution of the pigmentation over time.

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Prognosis

1. With cessation of laxative use, the pigmentation within the colonic mucosa typically diminishes over a period of months to years.
2. The mucosa gradually returns to its normal appearance, and the condition does not predispose individuals to an increased risk of colorectal cancer.

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Disclaimer- The views and opinions expressed in this article are those of the author and do not necessarily reflect the official policy or position of M3 India.

About the author of this article: Dr Jimmy Patel is a practising gastroenterologist in Chennai.