Is vitamin B12 malabsorption in bile fistula rats due to bacterial overgrowth? A study of bacterial metabolic activity in the small bowel.

To investigate whether vitamin B12 malabsorption in rats with choledochocolic fistulae is caused by bacterial overgrowth, we studied intestinal bacterial metabolic activity in choledochocolic fistula-operated rats, self-filling blind-loop-operated rats, and sham-operated rats. Fistula-operated rats had a moderate indicanuria compared with sham-operated ones, whereas the faecal excretion of nitrogen was unchanged. There was no difference in the amounts of radioactivity recovered in sediments of intestinal contents after an oral dose of 57CoB12, indicating unaltered bacterial uptake of vitamin B12 in fistula rats. The 14C-xylose breath test showed bacterial overgrowth in blind-loop rats only. Neomycin treatment of fistula rats diminished the excretion of indican but did not alter the absorption of vitamin B12. The results suggest moderately increased activity of indole-producing bacteria in fistula rats, but they do not support the hypothesis that vitamin B12 malabsorption is caused by bacterial overgrowth.