Functional adaptation of rat remnant colon after proximal hemicolectomy

Functional adaptation of the remnant intestine after extensive resection of small bowel is well documented. The effects of partial resection of large bowel on the remaining colon have not been characterized. Transepithelial potential (V_T), tissue resistance (R_T), and short-circuit current (I_sc) were measured in vitro across distal colonic tissue of rats three weeks after proximal hemicolectomy with ileotransversotomy and compared to the same parameters measured in the distal colon of control animals. In a second series of experiments, an in vivo perfusion technique was used to measure changes in sodium, potassium, and water transport in distal colon following proximal hemicolectomy. A 2.5-fold increase in V_T (P<0.01), a 62% increase in R_T (P<0.001), and a 35% increase in I_sc (P<0.05) were observed three weeks following hemicolectomy when compared to control animals. A 64% increase in net sodium absorption (P<0.025), no significant change in net potassium transport, and a 115% increase in net water absorption (P<0.01) were demonstrated in hemicolectomized animals when compared to control. It is concluded that in the rat the distal colon is capable of functional adaptation to increase net sodium and water absorption within three weeks after proximal hemicolectomy. The mechanism responsible for this adaptive process has yet to be defined. Our findings may explain the lack of chronic diarrhea in patients undergoing right hemicolectomy.