The estimation of the bile acids in the liver and changes in the mucosa of the small intestine after extensive resection of the small bowel are reported. It is shown that through the implantation of an isoperistaltic segment a delay of the intestinal passage was achieved, which resulted in better contact between chyme and intestinal mucosa, as well as in a faster and more prominent hypertrophy of the mucosa of the small intestine. As a consequence of the hypertrophy, the resorption of bile acids in the small intestine was much improved.