Ileal pouch-anal anastomosis, conventional ileostomy and ileorectal anastomosis modify cholesterol metabolism.

Proctocolectomy modifies the enterohepatic circulation and activity of bacterial enzymes depending on the structure of the stoma and function of the terminal ileum. We evaluated in our comparative study effects of different colectomy constructions on cholesterol metabolism. Levels of lipoprotein cholesterol and triglycerides, noncholesterol sterols, and squalene in serum, fecal fat, and bile acids, cholesterol absorption efficiency, and cholesterol metabolism by sterol balance technique were analyzed in human subjects with ileal pouch-anal anastomosis (n = 34), conventional ileostomy (n = 8), ileorectostomy (n = 6), and controls (n = 29). Malabsorption of bile acids, but not of fat, and low serum levels of total and low-density lipoprotein cholesterol, but high levels of high-density lipoprotein cholesterol and increased cholesterol synthesis were evident in the colectomy groups. In contrast to the ileorectostomy group, expressing high absorption and biliary secretion of cholesterol, a low cholesterol absorption percentage accompanied by elevated serum proportions of cholesterol precursor sterols and phytosterols characterized the ileal pouch-anal anastomosis and conventional ileostomy groups. After colectomy, fecal excretion of secondary bile acids was low, whereas relative proportions of identifiable bile acids remained the same in each study group. Low serum levels of total and low-density lipoprotein cholesterol of colectomized subjects may decrease the risk of premature atherosclerosis. The favorable serum lipid profile was due to enhanced fecal loss of cholesterol as bile acids despite abnormally high cholesterol synthesis. Ileal dysfunction probably diminished cholesterol absorption in subjects with ileal pouch-anal anastomosis and conventional ileostomy, with no explanation for those with ileorectostomy with no clinical gastrointestinal dysfunction. Relative synthesis of identifiable primary bile acids remained unchanged postoperatively, but formation of secondary bile acids was weak due to scarce bacterial flora.