Small-bowel adaptation after colectomy in rats.

Colectomy with ileoproctostomy or ileostomy was performed in rats. The animals were killed at different time intervals after operation. In histological sections from the small intestine the total crypt cell number and vinblastine-arrested mitoses were counted, and the villus height was measured; these parameters were compared with the corresponding ones in unoperated controls and in rats subjected to ileal transection. After ileoproctostomy the rats remained in good condition, whereas ileostomy was followed by weight loss, debility and a great mortality. After ileoproctostomy, ileostomy and ileal transection there was an increased number of mitoses in the crypts during the 28 days' observation period, indicating an increased rate of cell proliferation. Increased villus height was observed after ileoproctostomy as well as after ileostomy. The mucosal hyperplasia may play a role for the increase in water and salt absorption capacity after colectomy. Probably, however, the hyperplasia of the small-intestinal mucosa cannot fully compensate for the loss of the colon in rats. Preservation of the absorptive function of the rectum, as in ileoproctostomy, is necessary for adequate water and salt absorption.