Short-chain fatty acids in the small-bowel bacterial overgrowth syndrome

The short-chain fatty acids (SCFAs) have been measured by gas chromatography in fasting jejunal secretions, saliva, and feces from 8 patients with the small-bowel bacterial overgrowth syndrome (BO) and 9 control patients; in jejunal secretions and saliva from 6 healthy subjects; and in feces from 20 healthy subjects. The concentrations of SCFAs (median (range), mumol/l) in jejunal secretions of BO patients were as follows: total, 990 (210-12,370); acetic acid, 650 (170-6770); propionic acid, 110 (16-3070); isobutyric acid, 26 (1-310); n-butyric acid, 90 (12-1340); isovaleric acid, 35 (2-680); n-valeric acid, 7 (3-200). In BO patients the total concentration of SCFAs in jejunal secretions was approximately four times higher than in control patients (p less than 0.01) and in healthy subjects (p less than 0.025). The relative distribution of the acids resembled the distribution found in feces more than that of saliva or the normal jejunal secretions. These findings indicate that patients with BO have a colon-like flora in the small intestine and that the main part of the SCFAs in the jejunal secretions of these patients is produced by the altered microbial flora in the jejunum. Combined with other tests, analyses of intestinal SCFAs may prove to be valuable in the diagnosis of small-bowel bacterial overgrowth.