Gallstones and Biliary Colic
Cholesterol or pigment stones form in a supersaturated gallbladder, and pain occurs only when a stone transiently obstructs the cystic duct against a contracting gallbladder: no sustained obstruction, no inflammation, no pain.
First principles
Stones form when bile becomes supersaturated
Bile normally holds cholesterol in solution as micelles with bile salts and lecithin. When cholesterol output rises relative to these solubilising agents (obesity, rapid weight loss, oestrogen, age), it precipitates out and nucleates into cholesterol stones. Pigment stones form by a different route: chronic haemolysis or biliary stasis and infection increases unconjugated bilirubin in bile, which then precipitates as calcium bilirubinate. Either way, the gallbladder is simply a reservoir where supersaturated bile has time to crystallise.
Educational content pending clinical review. Not medical advice.