Small bowel bacterial overgrowth is a common cause of chronic diarrhea

Often a cause for chronic non-specific diarrhea (> or =3 stools per day for more than 4 weeks) is not identified. Small bowel bacterial overgrowth (SBO) can occur without morphological damage and remains difficult to diagnose. Often diarrhea is treated empirically with antibiotics with a good response. The aims of the present study were first to investigate the prevalence of SBO in a consecutive series of patients with chronic diarrhea and second to compare the utility of duodenal fluid culture and (14)C-d-xylose breath/lactulose test in diagnosing SBO.

In the first study, the cause of chronic diarrhea was prospectively diagnosed in 87 subjects. In the second study, tests of SBO were compared in 18 subjects with chronic diarrhea and 15 subjects with reflux oesophagitis used as control subjects. Duodenal fluid was aspirated at endoscopy and cultured and later a (14)C-d-xylose breath/lactulose test was performed.

In the first study, SBO was present in 48% of those with chronic diarrhea. In the second study, the diarrhea group had an average (range) stool frequency of 5.5 (3-10) per day and had normal duodenal biopsies. A total of 33%, 50%, 67% of subjects had SBO by duodenal culture alone, by a (14)C-d-xylose breath/lactulose test alone and by a combination of both tests, respectively. In the control group, 0%, 13% and 13% had SBO by duodenal culture alone, by (14)C-d-xylose breath/lactulose test alone and by combination of tests, respectively.

Small bowel bacterial overgrowth is a common (33-67%) cause of chronic diarrhea.