<prompt> Which is true about gallstonesPigment gallstones are most commonBacterial nidus of infection may be seenEven if asymptomatic gallbladder should be removedThey are mostly solitary  <response>: Recently bacterial infection has been shown to play the role in pathogenesis of gallstone, this adds to the growing pool of studies finding an infectious nidus in these gallstones Brown stones are related to bile statsis and infection Gram negative bacteria E.coli and Klebsiella secretes beta-glucuronidase, which deconjugate soluble conjugated bilirubin Free unconjugated bilirubin precipitates and combines with calcium and bile to form brown pigment stones. Stones from whenever static foreign bodies are present in the bole duct stents or parasites such as clonorchis sinensis and Ascaris lumbricoides Ref: Sabiston 20th edition Pgno : 1492 