Does non-dysenteric intestinal amoebiasis exist?

Background Chronic abdominal pain and frequent bowel disturbance are common symptoms experienced by more than 15% of apparently healthy people. In areas endemic for Entamoeba histolytica infection, these symptoms are often diagnosed as non-dysenteric intestinal amoebiasis even though no causal relation between such symptoms and E histolytica has been established and clinical presentation of non-dysenteric intestinal amoebiasis and irritable bowel syndrome (IBS) is not distinct. This study was done to assess the clinical significance of E histolytica infection in causation of such symptoms. Methods Patients with symptoms suggestive of non-dysenteric intestinal amoebiasis were recruited from a survey to assess the prevalence of abdominal symptoms in the general population (group A; n=78) and from medical outpatient clinics (group B; n=66). Participants who had symp toms as well as symptom-free controls (group C; n=100) were clinically examined and underwent stool examination, amoebic serology, colonoscopic examination, histopathological examination of colonoscopic biopsy samples, and a trial of antiamoebic therapy (only for participants with symptoms) with metronidazole and mebendazole. Findings There were no significant differences between the 144 patients with symptoms and the 100 symptom-free controls in the proportion with E histolytica in stools (26 [18%] vs 18 [18%]), serological evidence of E histolytica infection (61 [42%] vs 41 [41%]), colonoscopic abnormalities (five of 66 vs one of 33), or histopathological abnormalities (36 [49%] of 73 vs ten [30%] of 33). Cyst positive and cyst-negative individuals showed no significant difference in serological evidence of E histolytic infection, histological abnormalities, or response to therapeutic trial with metronidazole. A diagnosis of IBS was suggested on the basis of consensus criteria and Kruis diagnostic index in 127 of 144 patients with symptoms. The diagnosis of non-dysenteric intestinal amoebiasis could be made in only one patient, who had relapse of symptoms within 6 weeks of antiamoebic therapy and therefore the relapse did not meet criteria for the diagnosis of non-dysenteric intestinal amoebiasis. More than 60% of cyst-positive as well as cyst-negative patients with symptoms showed either complete or partial response to treatment strategy for IBS. Interpretation Chronic bowel symptoms, such as pain in abdomen and frequent bowel disturbance, have no association with either past or present infection with E histolytica. Most patients with such symptoms are likely to have IBS. The clinical entity of non-dysenteric intestinal amoebiasis, if it exists, must be extremely rare.