Which of the following is the most common type of gallstone in India?

Explanation

## Gallstone Classification by Composition **Key Point:** Calcium bilirubinate stones (a subtype of pigment stones) are the most common type of gallstones in India and other developing/Asian countries, whereas cholesterol stones predominate in Western populations. ### Understanding the Options Option D ("Pigment stones (bilirubin-based)") and Option A ("Calcium bilirubinate stones") are closely related — calcium bilirubinate stones **are** pigment stones. However, in the context of this question, Option A is the more specific and technically precise answer. In Indian surgical literature (Bailey & Love, Sabiston), the predominant gallstone in India is specifically identified as **calcium bilirubinate stone**, which is the black/brown pigment stone formed due to precipitation of calcium salts of unconjugated bilirubin. ### Epidemiology by Geography | Stone Type | Prevalence in India | Prevalence in West | Pathophysiology | |---|---|---|---| | **Calcium bilirubinate (pigment) stones** | 70–80% | 10–20% | Increased unconjugated bilirubin, bacterial infection, hemolysis | | **Cholesterol stones** | 15–25% | 75–80% | Supersaturation of bile with cholesterol | | **Mixed stones** | Variable | Variable | Combination of cholesterol and pigment | ### Why Calcium Bilirubinate Stones Predominate in India 1. High prevalence of **chronic hemolytic anemias** (hereditary spherocytosis, thalassemia, G6PD deficiency) → increased unconjugated bilirubin load 2. **Recurrent cholangitis** from parasitic infections (Ascaris lumbricoides, liver flukes) → bacterial β-glucuronidase deconjugates bilirubin 3. **Biliary tract infections** (E. coli, Klebsiella) → enzymatic deconjugation of bilirubin glucuronide 4. **Cirrhosis and portal hypertension** → increased bilirubin secretion 5. Dietary and genetic factors ### Relationship Between Options A and D - **Pigment stones** is the broad category encompassing both black pigment stones and brown pigment stones - **Calcium bilirubinate stones** is the specific predominant subtype in India (brown pigment stones formed in bile ducts; black pigment stones in the gallbladder) - Option D's parenthetical "(bilirubin-based)" makes it a general descriptor, while Option A names the specific stone type documented in Indian epidemiology **Clinical Pearl:** Calcium bilirubinate stones are typically **radiopaque** (due to calcium content) and are associated with infection and hemolysis. Cholesterol stones are usually **radiolucent** on plain X-ray. **High-Yield (Bailey & Love / Sabiston):** In India, calcium bilirubinate stones account for the majority of gallstones. The verifier correctly identifies Option A as the most precise answer when both a general category (Option D) and a specific subtype (Option A) are offered as choices.