Effects of jejunoileal bypass on the enterohepatic circulation of bile acids, bacterial flora in the upper small intestine, and absorption of vitamin B12

Abstract Eleven morbidly obese patients were studied before and at various time intervals after jejunoileal bypass (JIB). Bile acid deconjugation was assessed with the bile acid breath test and bile acid absorption by analyzing the fecal excretion of both radioactively labeled and unlabeled bile acids. In addition, aerobic and anaerobic cultures of upper small intestinal aspirates, the Schilling vitamin B 12 absorption test, and fecal fat analysis were performed. All patients developed marked diarrhea and steatorrhea after JIB. The bile acid breath test was positive in all 11 patients after JIB. In 7 of the 11 patients, this test was already slightly positive before JIB. In every instance, however, the bile acid breath test became significantly more abnormal after the bypass operation. The fecal excretion of labeled bile acids increased significantly. However, the increase in the quantitative excretion of the bile acids did not reach statistical significance. The concentrations of bile acids in fecal water were considerably below the levels required to induce diarrhea. This was mainly the result of a low fecal pH and consequent low aqueous solubility. Jejunoileal bypass effected a major shift in fecal bile acids from the secondary bile acids, lithocholic acid and deoxycholic acid, to the respective primary compounds, chenodeoxycholic acid and cholic acid. There were no significant changes in the small bowel bacteriologic findings after JIB. In 5 out of the 9 patients in whom bacteriologic studies were performed, the cultures were positive before the operation. The Schilling vitamin B 12 absorption test showed in all patients a significant drop in the 24-hour urinary 57 Co excretion rate after JIB. In spite of this decrease, however, the Schilling test remained within normal limits in 4 of the 11 patients. It is concluded that bile acids are not involved in the causation of diarrhea in JIB and that bacterial overgrowth in the small intestine plays no significant role in the development of the severe malabsorption syndrome in this condition. These findings, in conjunction with those of the heterogeneity of the alterations in the enterohepatic circulation (in particular the excretion of bile acids) are consistent with the view that the diarrhea and the malabsorption syndrome are mainly the result of the reduction in the absorptive surface of the small intestine.