Gallstone Causes (Cholelithiasis)

Cholesterol gallstones in an opened gallbladder with thickened, fibrotic wall from chronic cholecystitis

Gallstones affect 10-20% of adults in Western countries and about 1 million new cases are diagnosed annually in the United States. There are two fundamentally different types of stones, each with distinct causes.

1. Cholesterol Stones (80% in the West)

Cholesterol is solubilized in bile by bile salts and lecithins. When cholesterol concentration exceeds the solubilizing capacity of bile - a state called supersaturation - cholesterol crystallizes out of solution. Three interacting mechanisms drive this:

A. Bile Supersaturation with Cholesterol

Obesity and metabolic syndrome - increase hepatic cholesterol secretion into bile
Rapid weight loss - mobilizes peripheral cholesterol that floods into bile
Insulin resistance - alters bile acid metabolism
Estrogens - increase hepatic cholesterol uptake and synthesis, causing excess biliary cholesterol secretion

B. Crystal Nucleation and Growth

Once supersaturated, cholesterol crystals nucleate faster than they can be flushed out
Mucus hypersecretion traps crystals, enhancing aggregation into stones

C. Gallbladder Hypomotility / Stasis

Any condition that reduces gallbladder emptying promotes stone formation:

Pregnancy - progesterone slows smooth muscle motility; estrogens also increase bile lithogenicity
Prolonged fasting / total parenteral nutrition (TPN) - gallbladder isn't stimulated by CCK
Vagotomy - disrupts neural control of gallbladder contraction
Spinal cord injury

2. Pigment Stones (Predominantly in Asia and developing countries)

These are made of insoluble calcium bilirubinate salts. They form when bile contains excess unconjugated bilirubin.

Black Pigment Stones (found in sterile gallbladder bile)

Caused by conditions producing chronic hemolysis, which floods the bile with unconjugated bilirubin:

Sickle cell anemia - by age 10, at least 14% of children have gallstones; 36% by age 10-20
Hereditary spherocytosis
Thalassemia
Cirrhosis - reduced bile salt synthesis impairs bilirubin solubilization

Brown Pigment Stones (found in infected biliary ducts)

Caused by biliary infection - bacteria (e.g., E. coli, liver flukes like Clonorchis sinensis) produce phospholipases that release fatty acids from lecithins, forming calcium soaps. Common in Asia.

Summary Table of Risk Factors

Category	Cholesterol Stones	Pigment Stones
Demographics	Northern Europeans, Native Americans, North/South Americans	Asian, non-Western populations
Age	Advancing age (>80 yrs: 25-30%)	Any age
Sex/Hormones	Female sex, oral contraceptives, pregnancy	-
Metabolic	Obesity, insulin resistance, rapid weight loss	-
Hemolysis	-	Sickle cell, spherocytosis, thalassemia
GI disorders	Ileal disease (Crohn), ileal resection (disrupts bile acid enterohepatic cycling)	Crohn disease, ileal resection, cystic fibrosis
Hepatic	Inborn errors of bile acid metabolism, dyslipidemia syndromes	Cirrhosis
Infection	-	Biliary infection, liver flukes
Genetic	~25% heritable; ABCB4, ABCG5/G8 mutations	UGT1A1 polymorphism (Gilbert syndrome)
Iatrogenic	TPN, prolonged fasting, fibrates (increase cholesterol secretion)	-

Key Pathogenesis Summary

Cholesterol stones = bile supersaturation + nucleation + stasis
Pigment stones = excess unconjugated bilirubin (hemolysis) or biliary infection (bacteria hydrolyze conjugated bilirubin)

Sources: Robbins & Kumar Basic Pathology, p. 630; Robbins, Cotran & Kumar Pathologic Basis of Disease, Table 18.11; Sleisenger and Fordtran's Gastrointestinal and Liver Disease, Table 62.2

Recent evidence note: A 2026 Mendelian randomization meta-analysis (PMID 40064441) found causal links between gastrointestinal inflammation and gallstone formation, supporting the known association with inflammatory bowel disease. A 2025 systematic review (PMID 40499738) confirmed GLP-1 receptor agonists (e.g., semaglutide) are associated with gallstone and cholecystitis risk - likely through rapid weight loss and altered gallbladder motility - an increasingly relevant cause given widespread use of these drugs.

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