Alterations of the enterohepatic circulation of bile acids in patients with Crohn's disease (CD) and ulcerative colitis (UC) are known, but fecal bile acid patterns are less well defined. In this study total and individual fecal bile acids of 10 patients with CD (8 patients without bowel resection) 6 patients with UC and 5 healthy volunteers (HV) were determined by capillary gas chromatography. In comparison to HV (782 + 82 mg) the daily fecal excretion rate of bile acids was increased in CD (2,739 +/- 877 mg) and decreased in UC (409 +/- 55 mg). CD (80 +/- 19%) and UC (83 +/- 7%) had mainly primary bile acids, while secondary bile acids were predominant (80 +/- 4%) in HV. Bacterial conversion from primary to secondary bile acids is likely to be altered by rapid mouth-anus transit time (52 +/- 21 min) in UC and in CD by acidic stool pH (5.2 +/- 0.5). This lack of intestinal secondary bile acids may have pathophysiologic significance.