[Mucosal hyperplasia of the ileum after subtotal colectomy in rats]

To evaluate factors contributing to ileal mucosal hyperplasia following extensive colectomy, the following three models were designed in rats: Subtotal colectomy and end-to-end ileoproctostomy; retransection of the terminal ileum with end-to-side proximal-ileoproctostomy (colectomy group), End-to-side ileoproctostomy without colectomy (bypass group), and End-to-side ileocecostomy (control group). In all groups the terminal ileum was left out of the intestinal stream as defunctionalized segments. Specimens were obtained from the terminal ileum during operation and from both the functioning and the defunctionalized segments at various intervals postoperatively. The mucosal hyperplasia was evaluated by measuring eight variables including numbers of villi around the bowel circumference, villous height, crypt depth, total mucosal thickness, epithelial cell counts per villus, DNA contents per unit length of the bowel and radioactivity of incorporated 3H-thymidine as well as DNA specific activity. The results showed that marked mucosal hyperplasia of the functioning segments was noted in all groups, and that mucosal hyperplasia was also observed in defunctionalized segments of colectomized rats, but not in those of both bypass rats and control. These findings were statistically confirmed by analysis of variance. It was concluded that although intraluminal factors played an important role in mucosal hyperplasia of the ileum following extensive colectomy, humoral factors might be also involved in intestinal adaptation.