Figure 1. Key events in cholesterol gallstone formation, expressed as a Venn diagram. Excess cholesterol secretion causes bile to become supersaturated. This results in the production of pronucleating proteins (including mucins), which precipitate cholesterol microcrystals (shown as a notched rhomboid). Excessive bile cholesterol also becomes incorporated into the sarcolemma of smooth muscle cells, lessening gallbladder contractility. The resultant stasis traps the microcrystals of cholesterol in a mucin gel, allowing them to agglomerate, attract other insoluble components of bile (such as bile pigment and calcium), become biliary sludge and grow into overt gallstones.