Electron Microscopy of Small Intestinal Mucosa in Pancreatic Insufficiency

Abstract

The mechanism of fat absorption in pancreatic insufficiency was investigated in 4 patients. Jejunal contents were analyzed chemically, and jejunal mucosal biopsies were studied electron microscopically after intragastric test meals. Low amounts of lipolytic activity were found in postprandial jejunal contents; lipolysis of the test meal was reduced, but 2 ± 0.7 mm free fatty acid was solublilized in the aqueous phase of intestinal contents. In spite of these appreciable quantities of solubilized free fatty acids, no evidence of fat absorption was detected morphologically. Lipolysis, and the number of fat droplets in absorptive cells, could be normalized by adding 5 g of pancreatic enzymes to the test meal, indicating that there was no intrinsic mucosal defect. Fat absorption was also morphologically normal after feeding a predigested meal whose enzymes were inactivated, suggesting that pancreatic enzymes did not play a major role in enhancing absorption of solubilized free fatty acid. Lipolysis was low and mucosal fat droplets were absent in the proximal ileum, indicating that digestion and absorption of the test meal were not occurring in the distal small intestine. Despite absent morphological evidence of fat absorption, our patients absorbed 30 to 70% of their dietary fat. We speculate that in pancreatic insufficiency, fatty acids enter and leave the absorptive cells as monomers, or as small aggregates which are not detected by present electron-microscopic techniques.