Characteristics of endoscopic and pathological findings of amebic colitis

The clinical features of amoebic colitis resemble those of inflammatory bowel disease (IBD), and therefore the risk of misdiagnosis is very high. The aim of this study was to analyse the characteristics of the endoscopic and pathological findings of amebic colitis and the lessons from our patients, which were useful for diagnosing the amebic colitis timely and avoiding the serious complication.

We retrospectively reviewed data of all amebic colitis admitted to Beijing Friendship Hospital from January 2015 to January 2020. Cases were diagnosed by clinical presentation, laboratory examinations, and colonoscopy with biopsy and histological examination, no ELISA stool antigen or PCR tests were used.

16 patients were diagnosed with amebic colitis by the colonoscopy accompanied by biopsy and microscopic examination. At first time, 12 (75%) patients were misdiagnosed as IBD. Cecum was the most common site of amebic colitis (100%), and the caecum and rectum were also involved in many lesions (68.75%). Multiple lesions of erosion and/or ulcer were recognized in all patients (100%).The endoscopic findings included multiple irregular shaped ulcers and erosions with surrounding erythema, and the ulcers and erosions were covered by the white or yellow exudates. The intervening mucosae between the ulcers or erosions were normal. The features of rectums can be divided to 2 types: in 6 patients (54.5%), the irregular ulcer or erosions covered with white or yellow exudates were observed in rectum and cecum, and the bloody exudates in rectum were more severe than those in cecum; in other 5 patients (45.5%), rectal lesions were much less severe than those in cecum, the small superficial erosion or reddened mucosa were observed in the rectal ampulla. All patients were diagnosed as detection of amebic trophozoites from HE-stained biopsy specimens. The number of trophozoites ranged from 1/HPF to > 50/HPF. Among 16 cases, mild architectural alteration of colon crypt were observed in 10 cases (62.5%), and serious architectural alteration of colon crypt was found which had crypt branch in 1 case (16.7%). Cryptitis was observed in 12 cases (75%) and its severity was mild or moderate. No crypts abscess was observed in all cases.

The colonoscopy with histological examination are very important to diagnose the amebic colitis. Detect the amoebic trophozoites in the exudates by histological examination is the vital. Sometimes a negative biopsy does not rule out amebiasis, repeated biopsies may be needed to make the diagnosis.