Paper II
Question
Etiology and types of gall stones
Answer
Aetiology
Cholesterol stone formation
- Cholesterol supersaturation of bile (relative to bile salts and lecithin) — from increased cholesterol secretion (obesity, oestrogen, high-calorie diet) or decreased bile salt/phospholipid secretion
- Gallbladder hypomotility/stasis (pregnancy, rapid weight loss, fasting) — allows nucleation and crystal growth
- Nucleation factors
Pigment stone formation
- Black pigment stones: Increased unconjugated bilirubin from chronic haemolysis (e.g., hereditary spherocytosis, sickle cell disease) or cirrhosis
- Brown pigment stones: Associated with biliary tract infection/infestation (bacterial or parasitic, e.g., Clonorchis sinensis), causing bacterial deconjugation of bilirubin
Risk factors (classic “5 F’s” for cholesterol stones)
- Female, Fat (obesity), Fertile (multiparity), Forty (age), Fair (though ethnicity/genetic predisposition is the more accurate underlying factor)
Types of gallstones
- Cholesterol stones: Pale yellow, often solitary or few, radiolucent (usually not visible on plain X-ray)
- Pigment stones:
- Black pigment stones — small, hard, often multiple, associated with haemolysis/cirrhosis, usually radiopaque
- Brown pigment stones — soft, greasy, laminated, associated with biliary infection
- Mixed stones: Most common type in practice, composed of both cholesterol and pigment/calcium salt components, often faceted from mutual contact