Lack of relationship between serum and gallbladder bile calcium in patients with gallstone disease

BACKGROUND: Recent studies suggest that alternation in serum calcium influences the level of gallbladder bile ionized calcium (Ca2+). Theoretically, this could increase the risk of calcium precipitation in the gallbladder. METHODS: We therefore measured serum and gallbladder bile minerals in patients with gallstones (n = 27) and without (n = 10, controls). The serum samples were taken just prior to induction of anaesthesia and gallbladder bile was aspirated before any manipulation of the gallbladder. RESULTS: The active molality of Ca2+ in gallbladder bile was not statistically significant different between cases and controls (0.44 +/- 0.16 vs. 0.40 +/- 0.10 mmol/kg), whereas pH was significantly lower (6.94 +/- 0.31 vs. 7.36 +/- 0.28, p < 0.0001) and cholesterol higher (4.37 +/- 2.70 vs. 1.79 +/- 1.33 mmol/l; p < 0.01) in gallbladder bile obtained from cases. Serum Ca2+ at actual pH, magnesium and phosphate were significantly higher among cases than in controls. Gallbladder bile active molality of Ca2+ was significantly correlated with bile total calcium in both groups (r = 0.72; p < 0.001 and r = 0.91; p < 0.001, respectively). In controls only, we observed a positive relationship between serum Ca2+ at actual pH and the active molality of Ca2+ in bile (r = 0.61; p < 0.05). CONCLUSION: Our study demonstrates that Ca2+ in gallbladder bile does not differ between cases and controls. The lack of correlation between serum and gallbladder bile constituents in cases compared to controls suggests that changes in calcium equilibration between bile and serum in patients with gallstone disease might be of importance for the formation of gallstones.