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 symptoms 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.