Pathophysiology and significance of malabsorption after Roux-en-Y reconstruction.

Extensive metabolic studies were conducted in five normal controls and in five study patients after total gastric resection with Roux-en-Y (RY) reconstruction to determine the nutritional consequences of this particular technique of restoring gastrointestinal continuity. Although malabsorption of fat (19.2 +/- 2.2%) and nitrogen (22 +/- 2.5%) demonstrated in the study patients was moderate, it was significantly greater than normal ( less than 0.01). In spite of the demonstrated malabsorption, however, positive nitrogen balances (+ 0.33 +/- 0.18 gm/day) were maintained in the RY patients throughout the investigative period. These observations suggest that malabsorption after RY is infrequently of clinical significance, even in this "worst-case" situation characterized by complete removal of gastric tissue. Malnutrition should occur in only those patients with more limited gastric resections and RY reconstruction who are unable to increase caloric intake to cover losses due to malabsorption. A significant decrease in both trypsin and lipase concentrations and a marked delay in secretion of these enzymes was noted in the RY patients in response to a test meal (p less than 0.01). Malabsorption of fat and nitrogen in RY patients improved after exogenous pancreatic enzymes, but not after administration of tetracycline. Bacterial overgrowth as a cause of postoperative malabsorption may be less important than previously thought. Malabsorption after RY is due primarily to maldigestion brought about by duodenal bypass which, in turn, results in either an absolute or a relative pancreatic enzyme insufficiency.