Amebic colonic stricture: An unusual presentation.

Entamoeba histolytica infection can lead to colitis, peri-colic abscess, ameboma, perforation and rarely colonic stricture. Amebic colitis is usually managed with medical management and rarely needs surgical management. We hereby report a case of colonic amebiasis, presenting as a stricture in transverse colon, mimicking malignancy, and managed successfully.

INTRODUCTION

Benign strictures in colon are not infrequent. The various etiologies of benign colonic strictures are tuberculosis, ischemic colitis, inflammatory bowel disease, radiation colitis, and amebic colitis.[1] Colonic amebiasis is usually diagnosed clinically; however, it may masquerade as malignancy and can lead to a diagnostic dilemma.[2] Hereby, we present a case of a stricture in the transverse colon secondary to amebiasis which was managed surgically. To our knowledge, this is the first case report of amebic stricture in transverse colon.

CASE REPORT

A 45-year-old male presented to our hospital with complaints of pain in central abdomen, colicky in nature, associated with abdominal distension, and obstipation for the past 4 days. He had a history of altered bowel habits since the last 3 months and was on irregular medications. He had no symptoms of vomiting, bleeding per rectum or fever. He had undergone appendicectomy ~20 years back and inguinal hernia repair ~15 years back. Abdominal examination revealed abdominal distension and mild tenderness. No abnormality was detected on per rectal examination.

Laboratory investigations revealed leukocytosis with neutrophilia. Contrast-enhanced computerized tomography scan of the abdomen showed short-segment stricture in transverse colon with adjacent mesocolic fat stranding and haziness with subcentimetric lymph nodes [Figure 1a and b]. Proximal transverse colon and ascending colon were dilated with competent ileocecal valve. All findings were suspicious for malignant etiology rather than benign pathology of the transverse colon. Colonoscopy was performed that revealed circumferential stricture with ulcerohypertrophic mucosa in mid transverse colon and scope was not negotiable beyond that. Biopsy was taken, however, it was inconclusive.

Figure 1

(a) Contrast-enhanced computed tomography of the abdomen-axial; (b) coronal reformat-shows a stricture in the transverse colon (arrow) with adjacent mesocolonic fat stranding and dilated proximal colon

Given symptoms of obstruction and suspicion of malignancy, emergency laparotomy was done. Stricture with thickening was noted in the middle of transverse colon with proximal dilated colon and few sub-centimetric lymph nodes [Figure 2a and b]. Resection of diseased segment as per oncological principle and colo-colic stapled anastomosis was performed. The recovery of the patient was uneventful.

Figure 2

(a) Stricture in transverse colon (arrow) with proximal dilated colon intra-operatively; (b) cut open specimen showing stricture with ulceration (pointing forceps)

Histopathology specimen revealed ulcerated mucosa with exudates and granulation tissue, dense transmural inflammatory infiltrate comprising of neutrophils, lymphocytes, plasma cells, and macrophages. Trophozoites of Entamoeba histolytica (EH) were seen along with few multinucleate histiocytes. Submucosal and subserosal fibrosis, congested blood vessels and hyperplastic muscularis propria were seen [Figure 3a and b]. Later, the patient was commenced on oral metronidazole 400 mg 8 hourly and recovered well.

Figure 3

(a) Histopathology slides depicting-ulceration with fibrinous exudate and granulation tissue (H and E, ×10); (b) PAS stain (×40) highlighting trophozoites of Entamoeba histolytica

DISCUSSION

Amebic colitis is an infectious disease caused by EH. It can be grouped into superficial and invasive variants. Superficial ulceration involves primarily mucosa; however, it may progress to transmural necrosis and ulceration due to amebic invasion of the vessels, with subsequent thrombosis.[3] With ulceration and secondary infection, the patient may present with acute symptoms and signs. The bowel obstruction in amebiasis is likely caused by ameboma, pericolic abscess, intussusception, or stricture formation, as the patient in the present case.

Amebomas are chronic colonic amebiasis due to repeated invasion of the intestinal wall by EH. The majority of amebomas occur in the cecum, usually present as a mass and masquerade as malignancy.[2] Similarly, amebic stricture has also been reported in colon but occurs very rarely.[45] The most frequent sites are the cecum, ascending colon, and rectum. However, we encountered stricture in transverse colon secondary to amebiasis that has not been reported previously in English literature.

Usual features on colonoscopy such as ulcers with and without exudate, erosion, multiple lesions, and the presence of edematous mucosa are contributory to the diagnosis.[6] Colonoscopic biopsies are routinely performed for the diagnosis of amebiasis and confirmatory if trophozoites of EH are identified. However, the diagnostic accuracy to identify amebae were 11.4%–14.8% on biopsy specimens as reported by Smith.[5] Similarly, biopsy report was also inconclusive in our case. In addition, other common causes of colonic stricture such as tuberculosis, inflammatory bowel disease, or malignancy should be excluded histologically.

Amebic colitis and strictures generally resolve after medical management. Metronidazole, a potent, nontoxic systemic amebicide leads to response in most of the patients. However, nonresponders and persistent strictures may require surgical intervention in less than a percent of cases.[5] Even those patients requiring semi-emergency surgery should be placed on anti-amebic therapy for several days before operation and elective surgery should be delayed until completion of a full course of treatment.

Amebic strictures can be short or long with complete obliteration of lumen which require resection and side-to-side bowel anastomosis. In the light of amebic infection, metronidazole therapy should be initiated postoperatively.

To conclude, amebic colitis may complicate as stricture infrequently. Anti-amebic therapy should be initiated early on the basis of either clinical or colonoscopic findings after diagnosis. Amebic colitis may need surgical intervention in nonresponders or if the dominant stricture is causing acute intestinal obstruction.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.