The etiology of
biliary tract cancer is obscure, but there are evidences that
bile acid plays a role in
carcinogenesis. To find the association between
biliary tract cancer and
bile acid, this study compared the
bile acid concentration and composition among patients with biliary
cancer, biliary tract stones, and no biliary disease. Bile was compared among patients with
biliary tract cancer (n = 26), biliary tract stones (n = 29), and disease free controls (n = 9). Samples were obtained by percutaneous transhepatic biliary drainage, endoscopic nasobiliary drainage, or gallbladder
puncture, and analyzed for cholic, deoxycholic, chenodeoxycholic, lithocholic, and
ursodeoxycholic acid composition. Total
bile acid concentration was lower in the
cancer group than the biliary stone and control groups; the proportions of deoxycholic (2.2% vs. 10.2% and 23.6%, p < 0.001 and p < 0.001, respectively) and
lithocholic acid (0.3% vs. 0.6% and 1.0%, p = 0.065 and p < 0.001, respectively) were also lower. This result was similar when disease site was limited to bile duct or gallbladder. Analysis of cases with
bilirubin <or= 2.0 mg/dL also showed lower total
bile acid concentration and
deoxycholic acid composition in the
cancer group compared to controls (5.7% vs. 23.6%, p = 0.003). Although the presence of
bile duct obstruction explains some of the difference in total concentration and composition of
bile acid, there are other contributing mechanisms. We suspect the alteration of
bile acid transport might decrease
bile acid excretion and cause the accumulation of carcinogenic
bile acid in bile duct epithelium.