Characteristics of Endoscopic and Pathological Findings of Amebic Colitis

Abstract Background The clinical features of amoebic colitis resemble those of Inflammatory Bowel Disease (IBD), and therefore the risk of misdiagnosis is very high.Methods We retrospectively reviewed data of all amebic colitis cases 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. Results 16 patients were diagnosed with amebic colitis by colonoscopies accompanied by biopsies and microscopic examinations. At first, 12 (75%) patients were misdiagnosed with IBD. The 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 ulcers were recognized in all patients (100%). The features of endoscopic findings included multiple irregularly 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 the rectums can be divided to 2 types: in 6 patients (54.5%), the irregular ulcers or erosions covered with white or yellow exudates were observed in the rectum and the cecum, and the bloody exudates in the rectum were more severe than those in the cecum; in the other 5 patients (45.5%), rectal lesions were much less severe than those in the cecum, and small superficial erosions 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 was observed in 10 cases (62.5%), and serious architectural alteration of colon crypt was found which had a crypt branch in 1 case (16.7%). Cryptitis was observed in 12 cases (75%) and its severity was mild or moderate. No crypts abscesses were observed in all cases. Conclusions Colonoscopies with histological examinations are very important to diagnose amebic colitis. Detecting the amoebic trophozoites in the exudates by histological examination is vital. Sometimes a negative biopsy does not rule out amebiasis, repeated biopsies may be needed to make the diagnosis.