FAT-ABSORPTION AFTER SMALL-INTESTINAL TRANSPLANTATION IN THE RAT

Background. Intestinal transplantation is now used for patients with s evere malabsorption, however, little data exists quantifying the abili ty of the graft to absorb fat. This study tested the hypothesis that i ntestinal transplantation would not affect the lymphatic or venous upt ake of fatty acids. Methods. A syngeneic rat model of intestinal trans plantation (SPT) with caval drainage of the graft was used. Control an imals underwent intestinal division and reanastomosis (n = 15 in each group), The animals were followed for 6 weeks, and fat absorption in v ivo was quantified. The animals were anesthetized, sampling catheters were placed in the jugular and superior mesenteric veins and in the me senteric lymphatic duct, and a feeding tube was passed into the duoden um. Animals were allowed to recover, and a steady-state duodenal infus ion of lauric (C12:0) and palmitic (C16:0) fatty acid emulsion was beg un. A radiolabeled pulse of lauric (C12:0) and palmitic (C16:0) fatty acid was then given, and the subsequent appearance in the lymphatic an d venous systems was quantified. Results. In vivo absorption of dietar y fat was preserved, but after transplantation the mesenteric lymphati c flow and cumulative lymphatic appearance of both labels was signific antly reduced (flow reduced from 4.8 +/- 1.1 in controls to 1.0 +/- 0. 29 ml/hr in transplant animals, whereas lauric acid absorption was 33 +/- 11.4% in controls vs, 7.5 +/- 2.5% in transplant animals), There w as a modest increase in the jugular venous appearance of the fatty aci ds (2.0 +/- 1.1% in transplant animals vs, 0.75 +/- 0.55% in controls for lauric acid; P < 0.05 for all comparisons). Absorption of lauric a nd palmitic acids was very similar, and there was no preferential abso rption detected in the portal venous system, Dye studies demonstrated lymphatic recannulization around the vascular anastomosis, into the re troperitoneum. Conclusions. These results suggest that in this model o f SIT, fat absorption via the mesenteric duct is reduced, but that com pensatory collaterals form into the retroperitoneal lymphatics, There was no evidence of any significant increase in portal venous uptake of fatty acids after SIT, nor of preferential absorption of medium-chain fatty acids, These results may have implications for patients after S IT.