Most faceted gallstones are formed in the

(B) Gall bladder # Pigment stones are seen in patients with haemolysis in which bilirubin production is increased.> Examples are hereditary spherocytosis, sickle cell anaemia, thalassaemia, malaria and mechanical destruction of red cells by prosthetic heart valves.> Pigment stones are found in the ducts of patients with benign and malignant bile duct strictures.> Pigment stones in Oriental countries are associated with infestations of the biliary tree by Clonorchis sinensis and Ascaris lumbricoides.> Escherichia coli is often found in the bile of these patients. This bacterium produces the enzyme t3-glucuronidase which converts the bilirubin into its unconjugated insoluble form.> These stones are often present throughout the biliary tree including the intrahepatic ducts.