80% of gallstones contain
**Core Concept**
The composition of gallstones is a key aspect of gastroenterology, with the majority being classified based on their primary constituent. Gallstones form in the **gallbladder** due to precipitation of components of **bile**. The most common type of gallstone is the cholesterol stone.
**Why the Correct Answer is Right**
Cholesterol stones account for about 80% of all gallstones and are primarily composed of **cholesterol**. They form when there is an imbalance in the composition of bile, leading to supersaturation with cholesterol. This can occur due to increased cholesterol secretion into the bile, decreased bile salt secretion, or abnormalities in bile lecithin levels.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while pigment stones do exist, they are less common than cholesterol stones.
**Option B:** Incorrect as it's not specified and not the most common component.
**Option C:** Incorrect as calcium bilirubinate stones are a type of pigment stone, not the primary component of the most common gallstones.
**Clinical Pearl / High-Yield Fact**
It's crucial to remember that the formation of cholesterol gallstones is multifactorial, including genetic predisposition, obesity, female gender, and certain dietary factors.
**Correct Answer:** D. Cholesterol