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Classify gallstones. Describe their pathogenesis, complications and the pathology of cholecystitis.

Pathology · 2nd Professional — Para-Clinical

Gallstones — Types and Composition

Cholelithiasis is the formation of calculi within the biliary tract, most often the gallbladder.

Type	Composition	Appearance	Associations
Cholesterol stones (about 80% in the West)	Over 50% cholesterol monohydrate	Pale yellow, ovoid, often solitary and large; radiolucent	The "four Fs" — Fat, Female, Forty, Fertile; also oestrogen and oral contraceptives, rapid weight loss, ileal disease, diabetes, family history
Pigment stones — black	Calcium bilirubinate; sterile bile	Small, black, multiple; often radio-opaque	Chronic haemolysis — thalassaemia, sickle cell disease, hereditary spherocytosis, malaria; cirrhosis
Pigment stones — brown	Calcium bilirubinate with bacterial deposits	Soft, greasy, laminated	Biliary infection and infestation — E. Coli, Ascaris, Clonorchis; commoner in Asia
Mixed	Cholesterol, pigment and calcium	Multiple, faceted, laminated — the commonest overall in India	Combination of the above

Only 10 to 20% of gallstones are radio-opaque, so a plain radiograph is a poor test; ultrasound is the investigation of choice with over 95% sensitivity

Pathogenesis

1. Supersaturation of bile with cholesterol — too much cholesterol or too little bile salt and lecithin to keep it in micelles → 2.
Nucleation — crystals form, promoted by mucin and by gallbladder hypomotility and stasis → 3.
Growth — crystals aggregate into stones → For pigment stones: increased unconjugated bilirubin from haemolysis, or bacterial beta-glucuronidase deconjugating bilirubin in infected bile

CLINICAL PEARL

Three factors are needed and stasis is the one most often forgotten. Supersaturated bile alone does not form stones — many people have lithogenic bile and no stones. It is hypomotility that allows crystals time to nucleate and aggregate, which is why pregnancy, rapid weight loss, prolonged fasting and total parenteral nutrition all predispose.

Complications of Gallstones

Site	Complication
Gallbladder	Biliary colic, acute and chronic cholecystitis, empyema, mucocoele, perforation, gangrene; carcinoma of the gallbladder
Bile ducts	Choledocholithiasis with obstructive jaundice; ascending cholangitis; secondary biliary cirrhosis; mirizzi syndrome
Pancreas	Acute pancreatitis — gallstones are the commonest cause worldwide
Intestine	Gallstone ileus — a large stone erodes through a cholecystoduodenal fistula and obstructs at the ileocaecal valve; air in the biliary tree on a plain film

Cholecystitis

Acute cholecystitis — 90% are calculous, from a stone impacted in the neck or cystic duct; chemical irritation by concentrated bile with secondary bacterial infection. The gallbladder is enlarged, tense, red and covered by fibrinous exudate; MURPHY sign is positive
Acalculous cholecystitis (10%) — in critically ill, ventilated, burned or post-operative patients; carries a higher risk of gangrene and perforation and is easily missed
Chronic cholecystitis — a shrunken, thick-walled, fibrotic gallbladder with a chronic inflammatory infiltrate and rokitansky–aschoff sinuses (mucosal herniations through the muscle wall)
Porcelain gallbladder — a calcified wall from chronic inflammation; associated with a substantially increased risk of carcinoma, and an indication for cholecystectomy

Applied Aspects

Most gallstones are asymptomatic and are found incidentally; only about 20% ever cause symptoms, so silent stones are generally not operated on
Laparoscopic cholecystectomy is the treatment of choice for symptomatic stones
ERCP removes stones from the common bile duct and relieves obstruction and cholangitis
Carcinoma OF the gallbladder is strongly associated with gallstones, present in 80 to 90% of cases, and is notably common in north India, particularly along the Gangetic belt; it presents late and carries a poor prognosis
Charcot triad (fever with rigors, jaundice, right upper quadrant pain) indicates ascending cholangitis, a surgical emergency; the addition of shock and confusion makes Reynolds pentad
Consider haemolysis in a child or young adult with pigment stones, and investigate for thalassaemia, spherocytosis or sickle cell disease

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