Brown pigment gallstones are formed due to:
Cholesterol supersaturation
Increased deconjugation of bilirubin glucuronides
Increased biliary bilirubin load
Increased pigment in bile
Characteristics of different types of gallstones and major risk factors for cholesterol gallstones Cholesterol stones Brown pigment stone Black pigment stone Main composition Cholesterol 50% bilirubin >50% bilirubin Colour Yellow-grey Brown Dark Brown-black Aetiology Cholesterol supersaturation Increased deconjugation of bilirubin glucuronides Increased biliary bilirubin load Ref: J Gastrointestin Liver Dis March 2011 Vol. 20 No 1, 9-11.