Gallstones (cholelithiasis)

Gallstones are the most common biliary pathology. Indeed, cholecystectomy is the commonest surgical procedure in the abdomen in the Western world. Gallstones are classified according to their chemical composition into cholesterol stones, mixed stones and pigment stones. Cholesterol stones consist almost entirely of cholesterol and are often solitary (cholesterol solitaire). Mixed stones account for 90 per cent of gallstones. Cholesterol is the major component. Other components include calcium bilirubinate, calcium phosphate, calcium carbonate, calcium palmitate and proteins. Usually they are multiple, and they are often faceted. Pigment stones are most common in the Far East and are composed almost entirely of calcium bilirubinate. They are mostly small and multiple. Some are hard and coral-like, whereas others are soft and really concretions of sludge rather than stones (Fig. 54.30).

Gas in gallstones

Rarely the centre of a stone may contain radiolucent gas in a triradiate or biradiate fissure and this gives rise to charac­teristic dark shapes on a radiograph — the ‘Mercedes Benz’ or ‘seagull’ signs.

Limey bile

‘Lime-water’ bile is revealed on a plain radiograph (Fig. 54.5) more clearly than if the gall bladder has been visualised by cholecystography. The opacity is the result of the gall bladder becoming filled with a mixture of calcium carbonate and calcium phosphate, usually the consistency of toothpaste. The condition tends to occur when there is a gradual obstruction of the cystic or common bile duct, for example due to chronic pancreatitis or carcinoma of the pancreas. Organisms are rarely grown from the emulsion.

Incidence of gallstones

A ‘fat, fertile, flatulent, female of fifty’ is the classical sufferer from symptomatic gallstones. Useful as this clinical memorandum is, it should be tempered with the knowledge that cholelithiasis occurs in both sexes from childhood to the centenarian. In men the disease tends to occur in the older age groups at which point the incidence is equal to that of women. Stones are rarer in Africa and in southern India, but not in north India.

Causal factors in gallstone formation

The aetiology of gallstones is probably multifactorial. Factors implicated are: (1) metabolic; (2) infective; and (3) bile stasis.

Cholesterol and mixed stones

Metabolic

Cholesterol, insoluble in water, is held in solution by a detergent action of bile salts and phospholipids with which it forms micelles (Fig. 54.31). Bile containing cholesterol stones has an excess of cholesterol relative to bile salts and phospholipids, thus allowing cholesterol crystals to form. Such bile is termed ‘supersaturated’ or ‘lithogenic’. Bile cholesterol increases with age and is raised in women, particularly those taking the contraceptive pill, in obesity and by clofibrate — a drug used in the treatment of certain hyperlipoproteinaemias. The concentration of bile salts in bile is reduced by oestrogens, and also by factors which interrupt the intrahepatic circulation of bile salts (e.g. ileal disease, resection or bypass and cholestyramine therapy). These conditions are all associated with an increased incidence of stones, but there are still some people with cholesterol supersaturation who remain free of stones, suggesting that there are other factors of importance.

Infection

The role of infection in causing stones is unclear. Often bile from patients with gallstones is sterile, but organisms have been cultured from the centres of gallstones: the radiolucent centre of many gallstones may represent mucus plugs origi­nally formed around bacteria (Moynihan’s aphorism: ‘A gall­stone is a tombstone erected to the memory of the organism within it’). Helicobacter pylori antigens have been isolated within gall bladders containing stones.

Bile stasis

Gall bladder contractility is reduced by oestrogens, in pregnancy and after truncal vagotomy, situations in which the incidence of gallstones is increased. Patients on long-term parenteral nutrition have a high incidence of stones. Lack of good oral intake precludes the release of cholecystokinin, the hormonal stimulant of gall-bladder contraction released from the duodenal mucosa.

Pigment stones are seen in patients with haemolysis in which bilirubin production is increased. Examples are hereditary spherocytosis, sickle cell anaemia, thalassaemia, malar­ia and mechanical destruction of red cells by prosthetic heart valves. Pigment stones are found in the ducts of patients with benign and malignant bile duct strictures. Pigment stones in Oriental countries are associated with infestations of the biliary tree by Clonorchis sinensis and Ascaris lumbricoides. Escherichia coli is often found in the bile of these patients. This bacterium produces the enzyme t3-glucuronidase which converts the bilirubin into its unconjugated insoluble form. These stones are often present throughout the biliary tree including the intrahepatic ducts.

  The effects and complications of gallstones

Stones are found throughout the biliary tract and their compli­cations relate to obstruction of the cystic duct, of the intra­hepatic radicals or of the ampulla of Vater. Obstructive complications may be aggravated by the presence of infection leading to cholangitis and abscess formation. Nevertheless, gallstones can be asymptomatic; it is estimated that between 85 and 90 per cent of patients who have gallstones remain asymptomatic. In the UK the prevalence of gallstones at the time of death is estimated to be 17 per cent and possibly increasing. Thus, the mere presence of gallstones is not an indication for a surgical approach. For this reason symptoms must be analysed with care. A typical patient may fulfil Saint’s triad having gallstones, diverticulosis of the colon and a hiatus hernia, yet with symptoms that cannot be directly contributed to any of these. When considering management of a patient with gastrointestinal symptoms it is important to take a specific history and consider whether or not the pain from which the patient suffers is typical or not of biliary tract disease.

Effects and complications of gallstones

   In the gall bladder:

  Silent stones

    Chronic cholecystitis

  Acute cholecystitis

    Gangrene

    Perforation

    Empyema

    Mucocele

    Carcinoma

   In the bile ducts:

    Obstructive jaundice

    Cholangitis

  Acute pancreatitis

   In the intestine:

  Acute intestinal obstruction (‘gallstone ileus)