Q1. Correct answer: A
Rationale
In the United States, pigmented stones (black and brown) are less common than cholesterol gallstones. Both types of pigmented stones contain an excess of unconjugated bilirubin and are composed of calcium hydrogen bilirubinate, which is oxidized and polymerized in the hard black stones but unpolymerized in softer brown stones. Black pigmented gallstones are frequently radiopaque and form in sterile bile. Risk factors for black pigmented stones include hemolysis (example, sickle cell disease), cirrhosis, cystic fibrosis, and diseases affecting the ileum (example, Crohn's disease). In contrast, brown stones are more likely to occur in the bile ducts, are radiolucent, and form secondary to biliary stasis (example, biliary stricture) and infection (example, Clonorchis sinensis).
Obesity, female sex, and hyperlipidemia are risk factors for cholesterol gallstone formation. Octreotide decreases gallbladder motility and long-term use can increase the risk of cholelithiasis.
References
1. Stinton LM, Myers RP, Shaffer EA. Epidemiology of gallstones. Gastroenterol Clin N Am. 2010;39:157-69.
2. Vitek L, Carey MC. New pathophysiological concepts underlying pathogenesis of pigment gallstones. Clin Res Hepatol Gastroenterol. 2012;36:122-9.
ginews@gastro.org
