Supersaturated bile from obese patients without gallstones supports cholesterol crystal growth but not nucleation

Cholesterol crystal formation was studied in gallbladder bile samples collected from 18 patients with cholesterol gallstones, 6 patients with black pigment stones, and 14 obese patients without gallstones. In the absence of seed crystals, bile from patients with cholesterol stones showed a much greater tendency to form cholesterol crystals in vitro than bile of similar cholesterol saturation from patients without cholesterol stones. The ability to form crystals was not related to the biliary hexosamine concentration, an indicator of mucin content. When small seed crystals of cholesterol monohydrate were added to each bile, the seed crystals dissolved in all biles (n = 8) with a cholesterol saturation index less than 0.76. In contrast, 29 of 30 biles with a cholesterol saturation index greater than 0.76 supported crystal growth, even when collected from patients without gallstones. These results indicate that the difference between supersaturated biles in the ability to form cholesterol crystals resides at the nucleation, rather than the growth, stage of crystal formation.