This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Anatomy
[{'content': 'Stone formation in gall bladder is enhanced by all except \nSelect and explain. \nA. Clofibrate therapy, B. Ileal resection, C. Cholestyramine therapy, D. Vagal stimulation', 'role': 'user'}, {'content': "Answer: D \nExplanation: Vagal stimulation increases GB motility and prevents Gallstone formation Factors responsible for formation of gallstones Lithogenic bile Increased biliary cholesterol--Obesity, cholesterol rich in diet, clofibrate therapy Decreased Bile acids - Primary biliary cirrhosis, OCP's, mutation of CYP7A1 gene, impaired enterohepatic circulation of bile acids Decreased Biliary Lecithin - MDR-3 gene mutation leads to defective secretion in bile Nucleation Cholesterol monohydrate Crystal aglomerate to become macroscopic crystal by nucleation Pro-nucleating factors - Mucin, Non-Mucin, Infection Anti-Nucleating factors - Apolipoprotein A-1 and A-II Excess of Pro-nucleating factors or deficiency of Anti-Nucleating factors results in formation of gall stones Stasis or GB hypomotility Prolonged TPN Prolonged fasting Pregnancy Octreotide OCP's Massive burns Ref: Sabiston 20th edition Pgno : 1492", 'role': 'assistant'}]