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Abstract
A patient was taken to the operating room with a presumptive diagnosis of necrotic small bowel and colon. During the procedure, it was noted that she had black mucosa throughout the colon. Several factors suggested viable colonic tissue, and the decision was made to not resect the colon as originally planned. Final pathology of the specimen would later reveal melanosis coli, an ultimately benign diagnosis. Further questioning of the patient found that she had taken a herbal laxative supplement containing several components which are known to cause melanosis coli. We hope that this case report will serve as a reminder to surgeons and clinicians to remember melanosis coli as a clinical entity when confronted with blackened or darkened colonic mucosa. On review of available literature, we identified other cases in which melanosis coli was discovered intraoperatively, and we propose a number of factors to support intraoperative decision making.
- General surgery
- Gastrointestinal surgery
- Drugs: gastrointestinal system
- Unwanted effects / adverse reactions
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- General surgery
- Gastrointestinal surgery
- Drugs: gastrointestinal system
- Unwanted effects / adverse reactions
Background
Originally described in 1830 by Jean Cruveilhier and later named in 1857 by Virchow, melanosis coli is a dark discolouration of colonic mucosa associated with chronic use of laxatives containing anthraquinones, such as senna, rhubarb, cascara and buckthorn.1–3 The discolouration is benign, ranges from dark brown to black or even a slight blue/purple hue. The condition is usually discovered visually during colonoscopy, when the mucosa is stretched by insufflation, demonstrating a characteristic pattern (figure 1).
Characteristic mucosal pattern of melanosis coli on stretch of the mucosa.1
The pigmentation seen in melanosis coli is reversible, resolving on laxative discontinuation. The mechanism is thought to derive from activation of laxative supplements leading to cell death and apoptosis in the lining of the colon. These cells then release lipofuscin which is consumed by macrophages within the lamina propria.4 Melanosis coli has also been seen in patients with inflammatory bowel disease, chronic diarrhoea and even non-steroidal anti-inflammatory drug use.1 2 Reports suggest the pigmentation may not be uniform and demonstrates higher intensity in the caecum and proximal colon versus the distal colon. This has been posited to be secondary to higher luminal concentrations in the proximal colon. Some studies have reported a linkage between colorectal cancer, melanosis coli and laxative use; however, these associations have not been convincingly determined.5–7 In addition, melanosis coli has been demonstrated to spare tissues later diagnosed as adenomas and carcinomas.7
Case presentation
The patient is a woman in her 60s, who was admitted to the hospital for shortness of breath, malaise and a cough for 11 days. The patient had tested positive for COVID-19 9 days prior and was not vaccinated. Her medical history was remarkable for hyperlipidaemia and breast cancer treated 20 years prior with lumpectomy and radiation therapy; she had declined hormonal therapy afterward. Surgical history was significant for a hysterectomy. She was diagnosed with COVID-19 pneumonia with superimposed bacterial infection, for which she was started on dexamethasone, remdesivir, cefepime, metronidazole and azithromycin. She was initially admitted to the COVID-19 ward on 6 L of oxygen via nasal cannula and was noted to have mild epigastric and right lower quadrant abdominal tenderness on initial examination. Over the following days, her oxygen requirements worsened, and the patient was transferred to the intensive care unit (ICU) for non-invasive ventilation on hospital day 5. At this time, the patient was noted to have leucocytosis with a white cell count of 18.6 x 109/L. The remainder of her laboratory work-up, including hepatic function panel and renal function panel, was within normal limits. CT angiography of the chest, abdomen and pelvis was obtained and demonstrated embolisation and partial infarction of the spleen, as well as dilation of the small bowel, concerning for ileus. Her dose of enoxaparin, initially started at prophylactic levels, was increased to 1 mg/kg, per hospital protocol based on serum D-dimer levels. The patient’s respiratory status waxed and waned over 3 weeks. She developed worsening abdominal pain and distention, and the surgical service was consulted for management.
Investigations
Her abdominal exam on initial surgical evaluation demonstrated tenderness across the lower abdomen, but no peritoneal signs were elicited. The CT of the abdomen was repeated, which revealed small pelvic fluid collections not amenable to percutaneous drainage. The patient was initially able to be weaned off supplemental oxygen and be transferred to the medical floor but eventually was transferred back to the ICU for increased respiratory requirements and intubation.
She became tachycardic on hospital day 20 and developed a worsened leucocytosis to 34.6 k/µL. A repeat abdominal CT scan showed persistent fluid collections in the lower abdomen/pelvis (figure 2), which remained unchanged. Because her abdomen became tense and distended with worsening leucocytosis and overall clinical deterioration, the surgical team made the decision to take her to the operating room for diagnostic laparoscopy with possible laparotomy to evaluate and drain the fluid collections.
Treatment
On entering the abdomen with the laparoscope, purulent fluid was identified in the right lower quadrant, consistent with the fluid collections identified on prior CT scans. Because of the distention of bowel, oedema and lack of adequate visualisation, the decision was then made to convert to an open laparotomy. After evaluation, 20 cm of necrotic terminal ileum was noted, as well as a dusky and non-viable right colon, and so an en bloc resection was performed of these tissues, with an end ileostomy in the right lower quadrant, as well as a mucous fistula in the right upper quadrant (figure 3). Black mucosa was encountered when the colon was opened, raising concern for further ischaemia and colonic necrosis, and another 7 cm of colon was resected (figure 4). However, black mucosa was again encountered when the colon was opened.
Initial right colon specimen with mucosal discolouration.
CT images demonstrating fluid collections in lower abdomen/pelvis (red arrow).
Extra segment of transverse colon with mucosal discolouration.
Differential diagnosis
At this point, the primary concerning diagnosis was continued ischaemia of the bowel. Melanosis coli was not considered in the operating room because the patient’s history of herbal supplement use would not be known until later pathology resulted. However, we proceeded with the decision to create the mucous fistula (figure 5) due to several factors. First, there was brisk bleeding from the submucosa and mesenteric vessels when the bowel was opened. There was also a patchwork of pink tissue underlying the black mucosa when it was stretched. We felt this was a superior option to resecting additional colon and risk future complications of subtotal colectomy. The mucous fistula would be observed closely for signs of bowel death in the postoperative period. The fascia was then closed, and the patient was returned to the ICU for recovery.
Mucous fistula with dark mucosa.
Outcome and follow-up
The patient’s postoperative course was prolonged. She had ileostomy output on postoperative day 6 and was extubated on postoperative day 15. The mucous fistula remained the same dark colour throughout her postoperative course, but it did not retract into the abdomen or exhibit mucosal sloughing. The patient was discharged to a long-term care facility on hospital day 39 (postoperative day 18). The patient has been seen in the office since discharge and has been slowly returning to her normal quality of life.
Pathology specimens revealed melanosis coli in addition to gross ischaemia and infarction of the terminal ileum. On further questioning of the patient, she reported using a herbal laxative called ‘lower bowel stimulator 2’ (LBS2, by Nature’s Sunshine Products, Lehi, Utah, USA) due to a long history of constipation. She had taken two capsules of this supplement daily for at least 10 years, though it should be noted that the product label warns against prolonged use of the supplement. LBS2 contains cascara sagrada bark, buckthorn bark and Turkey rhubarb root: three ingredients known to cause melanosis coli. She has since stopped taking this supplement.
Discussion
This case report presents a complex patient, diagnosed with melanosis coli, which influenced intraoperative decision making. Melanosis coli is noted in as many as 1.8% of colonoscopies.5 When the colon is insufflated and the mucosa is stretched, it adopts a characteristic pattern. However, when the colonic mucosa is not stretched, the bunched-up mucosa appears black, as is seen in necrosis. The condition is altogether benign and can be treated with cessation of the offending medication. Prior studies and reports have suggested an increased prevalence of colorectal cancer in patients with melanosis coli but have been unable to generate a definitive causation.2 5–7
Previous reports on this topic have been published with the key clinical question of distinguishing melanosis coli from ischaemic colitis.8–11 Two reports were identified in our review of the literature that affected intraoperative decision making.10 11 The authors of one report ultimately decided to perform a subtotal colectomy for presumed colonic ischaemia, with final pathology reporting melanosis coli and viable tissue.10 The authors of the second report incidentally discovered melanosis coli during surgery for a caecal volvulus.
Due to the extent of presumed ischaemia, they left the patient in discontinuity and consulted the pathologist to confirm viability of the colon. On confirmation of viable bowel, they then returned to the operating room 48 hours after the index surgery to perform anastomosis and abdominal closure.11
Our patient’s bowel likely infarcted secondary to her COVID-19 infection, a phenomenon which has been well documented over the course of the global pandemic.12–14 Our patient had already infarcted a portion of her spleen, likely due to the same aetiology. In the operating room, our team underwent much deliberation on the optimal course to take with the findings of black mucosa. Typically, this suggests ischaemic or necrotic bowel and necessitates resection. However, we identified several factors which ultimately steered us away from further colonic resection. Our decision was influenced by brisk bleeding from the submucosa and mesentery, the viable appearance of the exterior of the colon and the underlying pink tissue when the mucosa was stretched. These findings suggested healthy perfusion to the segment of colon in question. Our patient also lacked the classic medical history and other common findings to suggest ischaemic colitis (ie, visceral vascular disease, hypoperfusion state or dusky appearance of the exterior colon).15 Our hope is that this report will serve as a reminder to surgeons and clinicians to keep the possibility of melanosis coli in mind when confronted with black colonic mucosa. We feel that the combination of black colonic mucosa, brisk arterial submucosal bleeding and the characteristic appearance of the stretched mucosa of melanosis coli is key findings to help avoid potential unnecessary subtotal colectomy and its resultant ramifications on stoma reversal decisions and ultimate bowel function after stoma reversal.
A key limitation of this issue is the rare nature of the problem discussed. Melanosis coli is a well-described phenomenon on colonoscopies, but not as commonly discovered in the operating room. Our case provides insights, pearls and pitfalls but by no means makes this case discussion a summative opinion on best practice.
Learning points
Black colonic mucosa is not always due to ischaemia and necrosis, but those should always be the first considerations.
Melanosis coli can be caused by many herbal supplements.
Many tissue-specific factors should be considered before committing to a bowel or colon resection.
Ethics statements
Patient consent for publication
Acknowledgments
Judy Knight, MLS, AHIP, for her help in compiling relevant literature and assisting in publication.
Footnotes
Contributors GH was responsible for the planning of the report, the literature review, writing and editing of the manuscript. RP was responsible for the literature review, writing and editing of the manuscript. JC was responsible for the literature review, writing and editing of the manuscript. WC was responsible for planning of the report and editing of the manuscript. RR was responsible for editing of the manuscript and submission.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.