All of the following are essential for formation of gallstones except:

Factors Responsible for Formation of Gallstones Lithogenic bile Nucleation Stasis or GB hypomotility Increased Biliary Cholesterol: - Obesity - Cholestrol rich diet - Clofibrate therapy Cholesterol monohydrate crystal agglomerate to become macroscopic crystal by nucleation Pro-nucleating Factors: - Mucin - Non-mucin glycoprotein - Infection Anti-nucleating Factors: Apolipoprotien A-1 and A-2 Excess of pro-nucleating factors or deficiency of anti-nucleating factors results in formation of gallstones Prolonged TPN Prolonged fasting Pregnancy Octreotide OCPs Massive burns Decreased Bile Acids: - Primary biliary cirrhosis - OCP's - Mutation of CYP7A1 gene - Impaired enterohepatic circulation of bile acids:Ileal disease or resection, cholestyramine or colestipol (bile acid sequestrants) Decreased Biliary Lecithin: - MDR-3 gene mutation leads to defective lecithin secretion in bile