The effect of biliary bile acid concentration and composition on the calcium level in human gallbladder bile

We analyzed total and ionized calcium concentrations in gallbladder bile of 34 humans in four groups: 8 patients with no gallstone, 11 gallstone patients treated with no gallstone dissolution agents, 8 gallstone patients treated with chenodeoxycholic acid (CDCA) and 7 gallstone patients treated with ursodeoxycholic acid (UDCA). We found that total calcium level ranged from 1.40 to 8.01 mmol/liter, closely related to total bile acid concentration (r = 0.759). However, ionized calcium level was maintained in a narrow range of 0.25 to 1.23 mmol/liter and had no relation to total bile acid concentration. UDCA-rich bile showed relatively high level of ionized calcium. We performed ultrafiltration of bile with cut-off molecular weight 1,000 to investigate the interaction between biliary calcium and bile acid aggregates. The proportion of ultrafiltrated bile acid level to that in original bile in the UDCA group was statistically higher than the other groups. Relatively large percentage of smaller bile acid aggregates in UDCA-rich bile may impair its calcium solubility.