
==== Front
Int Med Case Rep J
Int Med Case Rep J
imcrj
International Medical Case Reports Journal
1179-142X
Dove

475869
10.2147/IMCRJ.S475869
Case Report
Colonoscopic Resolution of Melanosis Coli After Cessation of Senna Laxative Use
Chiba et al
Chiba et al
http://orcid.org/0000-0001-7072-3157
Chiba Toshimi 1 *
Wang Ting 1 *
Kikuchi Satoshi 2 *
1 Division of Internal Medicine, Department of Oral Medicine, Iwate Medical University, Morioka, Iwate, Japan
2 Department of Gastroenterology, Sanai Hospital, Morioka, Iwate, Japan
Correspondence: Toshimi Chiba, Division of Internal Medicine, Department of Oral Medicine, Iwate Medical University, 19-1 Uchimaru, Morioka, Iwate, 020-8505, Japan, Tel +81 19 651 5111, Fax +81 19 654 3281, Email toschiba@iwate-med.ac.jp
* These authors contributed equally to this work

11 9 2024
2024
17 783787
27 4 2024
20 8 2024
© 2024 Chiba et al.
2024
Chiba et al.
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Abstract

Melanosis coli occurs with the administration of stimulant laxatives for the relief of constipation. However, the duration of macroscopic improvement of melanosis coli after discontinuation of anthracene laxatives is not well understood. We describe the case of an 81-year-old female diagnosed with melanosis coli via colonoscopy who had been taking senna laxatives for 5 years. Seven months after cessation of senna laxatives, colonoscopy showed no melanosis coli in the colon. This impressive report describes the observation of melanosis coli with colonoscopy; 7 months after the withdrawal of senna stimulant laxatives, melanosis coli resolved.

Keywords

melanosis coli
colonoscopy
discontinued
senna laxative
anthraquinone
There were no funding sources There were no funding sources.
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pmcIntroduction

Melanosis coli demonstrates abnormal brown or black pigmentation of the colonic mucosa and frequently found in patients with stimulant laxatives use.1 It is often caused by the chronic use of anthracene derivatives, such as sennosoids and aloe.2,3 Stimulant laxatives can cause cellular damage to colonic epithelial cells, leading to apoptosis. Apoptotic cells are phagocytosed by macrophages and converted to brown lipofuscin pigment in the lamina propria, the coloration of melanosis coli may be due to accumulation of lipofuscin.4 Although melanosis coli did not represent a higher incidence of colorectal cancer compared with controls, clinical concern remains because melanosis coli is associated with a higher detection rate of colorectal adenoma.5–7 Melanosis coli can occur within only a few months of chronic laxative administration, and treatment of melanosis coli is stop laxative use.8,9 Once laxative use is halted, the dark pigmentations may resolve, it would take up to a year.10 The mean duration from the last diagnosis without melanosis coli to the time of initial diagnosis of melanosis coli was 24 months, whereas at least 2 years is period for melanosis coli to disappear.5 However, we do not know well the duration of macroscopic improvement of melanosis coli after discontinued anthracene laxatives. Here, we report a case of melanosis coli we could observe colonoscopy findings for 7 months after causative senna laxative cessation.

Case Report

An 81-year-old female had been an outpatient for treatment of hypertension for 10 years and was taking oral carvedilol 5 mg daily. She has been taking senna laxatives for 5 years because of constipation. She had been undergoing hemodialysis for about 2 years due to renal failure caused by membranous nephropathy. She underwent colonoscopy for further examination of constipation, a colonoscopy showed a sessile polyp in the sigmoid colon and revealed a brown and grey pigmented appearance throughout the colon, which was diagnosed as melanosis coli (Figure 1). We also graded the severity of melanosis coli (Grades I–III) based on the extent of pigmentation.7 Grade II melanosis coli was present in the rectum and descending colon, transverse colon, ascending colon and cecum, and Grade I melanosis coli was present in the sigmoid colon (Table 1). She was admitted to the hospital for a colon polypectomy. One year later, when the patient underwent colonoscopy for surveillance after colon polypectomy, colonoscopy findings showed that Grade II melanosis coli remained in the rectum, sigmoid colon, descending colon, ascending colon and cecum (Figure 2), and Grade III melanosis coli was present in the transverse colon. Then, the senna laxative was discontinued, and polyethylene glycol was administered. Seven months after cessation of senna laxatives, colonoscopy revealed that melanosis coli had disappeared in the rectum, sigmoid colon, descending colon, transverse colon, ascending colon and cecum (Figure 3).Table 1 Grades of Melanosis Coli Severity by Location in the Colon

	First Colonoscopy	One Year After First Colonoscopy	Seven Months After Withdrawal of Senna Stimulant Laxatives	
Cecum	Grade II	II	None	
Ascending colon	Grade II	II	None	
Transverse colon	Grade II	III	None	
Descending colon	Grade II	II	None	
Sigmoid colon	Grade I	II	None	
Rectum	Grade II	II	None	

Figure 1 Colonoscopy findings in the ascending colon after administration of senna laxatives for 5 years. Colonoscopy findings revealed a brown and grey pigmented appearance throughout the colon, which was diagnosed as melanosis coli Grade II in the ascending colon.

Figure 2 Colonoscopy findings in the ascending colon with continued administration of senna laxatives one year after the first colonoscopy. Melanosis coli Grade II was observed in the ascending colon.

Figure 3 Colonoscopy findings in the ascending colon 7 months after discontinuation of senna laxatives. Seven months after discontinuation of senna laxatives, colonoscopy revealed disappearance of melanosis coli.

Discussion

Colonoscopy reveals melanosis coli in patients receiving chronic administration of stimulant laxatives containing anthraquinone.1 These laxatives pass through the colon, with a direct toxic effect on colonic epithelial cells, and may cause cell damage in the colon, leading to apoptosis. The apoptotic cells, which are thought to be a precursor of pigmentation formation, are ingested by macrophages and converted into brownish lipofuscin pigment in the lamina propria.4

Severe abdominal symptoms would not occur in patients with melanosis coli; colonic motility might be suppressed because of impairment to the myenteric plexus.11 The age of onset is more than 60 years,10,12 and the incidence is higher in females than in males.12

Melanosis coli may develop 4 to 12 months after initiation of chronic laxative use.13 Melanosis coli is most commonly found in the proximal colon,3 probably due to the difference in the distribution of macrophages in the colon.10 The appearance of melanosis coli may vary throughout the colon on the basis of the amount of pigmentation or the amount of laxative absorbed.3 Stimulant laxatives inhibit epithelial tissue function, absorption, secretion and motility, and cause apoptosis, reflecting the qualitative and quantitative differences in colonic microbial flora.3 With the improvement of constipation symptoms and the withdrawal of laxatives, a large amount of lipofuscin is digested and decomposed by lysosomes, and pigmentation of melanosis coli can be alleviated and even disappear.14 In this case, 7 months after the discontinuation of senna laxatives, colonoscopy showed the disappearance of Grade II to III melanosis coli.

Melanosis coli has a higher detection rate of colorectal adenomas, while melanosis coli does not have a higher incidence of colorectal cancer compared to controls,5–7 the pathophysiology of these associations is not well understood. However, polypoid lesions appear pale and devoid of pigmentation in the colon.15 Because macrophages in the lamina propria are diminished in adenomas associated with melanosis coli,16 the presence of melanosis coli facilitates the detection of small adenomas in the colon.6,12 In one analysis, patients with melanosis coli were more likely to have an adenoma <5 mm.7 Some studies have suggested a possible relationship between melanosis coli and colorectal cancer risk;17 however, melanosis coli is not associated with a greater risk for colorectal cancer,10 and the association between melanosis coli and colorectal cancer is controversial. The rate of apoptosis in patients with colonic melanosis was significantly higher than that of controls.16,18 The expression of p53, bcl-2, and Ki-67 was increased in severe melanosis coli compared with mild melanosis coli and controls.18 G-protein subunit γ 5 (GNG5) and lysophosphatidic acid receptor 3 (LPAR3) might be candidate biomarkers associated with apoptosis in melanosis coli.19

The prognosis of melanosis coli is favorable.6 It typically resolves with causative laxative cessation; however, rebound constipation can result. Recently, instead of stimulant laxatives, polyethylene glycol, secretagogues such as lubiprostone, and ileal bile acid transporter inhibitors such as elobixibat were recommended for constipation.20,21 In this case, the patient was on hemodialysis, but there are no reports on the relationship between melanosis coli and hemodialysis.

Histopathological follow up of the colonoscopy was not identified in this case, further investigation is required to confirm both colonoscopy findings and pathology examinations. The function of melanosis coli is still unclear, and its pathophysiology must be clarified.

In conclusion, this report describes the observation of melanosis coli with colonoscopy; 7 months after the withdrawal of senna stimulant laxatives, melanosis coli resolved. Histopathological follow up of colonoscopy should be considered in the future.

Ethics Statement

Based on the regulations of Iwate Medical University, institutional review board approval is not required for case reports.

Consent for Publication

Written informed consent was obtained from the patient for publication of this case reported and any accompanying images.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

The authors declare no conflicts of interest in this work.
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