gall bladder

gall bladder The gall bladder receives bile from the liver, stores and concentrates it, and delivers it to the intestine as required. It is a slate-blue sac, partly sunken in a groove on the under surface of the right lobe of the liver. It is 7–10 cm long, 3 cm in maximum breadth and, under usual circumstances, has a 30–50 ml capacity. Bile acids and other constituents of bile produced in the liver are carried to the gall bladder via the hepatic and cystic ducts. A 10-fold concentration effect is achieved by the transport of water from the bile to the bloodstream within the gall bladder wall. When fatty food passes from the stomach into the intestine, the gall bladder is stimulated to contract by cholecystokinin, a hormone released from the lining of the intestine. Concentrated bile is then released into the intestine via the cystic and common bile ducts. The high concentration of bile acids turns fat in the diet into an emulsion which is easily digested by the action of the enzyme lipase from the pancreas, and absorbed across the intestinal wall. The efficiency of this system is enhanced by the reabsorption of bile acids from the intestine, minimizing the quantity lost in the faeces. Reabsorbed bile acids are then carried by the bloodstream back to the liver, where they are available for further recycling into the bile. If the gall bladder has to be removed, unconcentrated bile drains directly into the intestine from the liver, but in most people digestion of fatty food can still occur quite adequately.

The formation of gallstones within the gall bladder represents the most common cause of gall bladder disease. Gallstones were first described by Gentile da Foligno in Padua in 1341, who noted many stones within the post-mortem gall bladder of a woman whose viscera had been removed so that the body could be embalmed. Gallstones occur commonly in people of all races and at all ages (even in the teens). Although their prevalence varies, there is some truth in the well-known aphorism that the typical patient with gallstones is a fat, fair, fertile woman in her forties.

Bernard Naunyn's classic monograph published in 1892 is credited as containing the first discussion of the chemical composition of gallstones. It is now common to speak of three types of gallstone: pigment, cholesterol, and mixed. Patients with excessive breakdown of their red blood cells, resulting in increased production of bilirubin, are at increased risk of the formation of pigment gallstones, which are predominantly composed of calcium bilirubinate, carbonate, phosphate, and palmitate. Conversely, supersaturation of bile with insoluble cholesterol, as a result of metabolic defects, promotes the formation of cholesterol gallstones.

Autopsy series suggest that gallstones are formed in at least 15% of the adult population, the majority of whom have never experienced symptoms. Indeed, it has been estimated that only about 1% of people with gallstones will develop complications of them each year. These occur when gallstones obstruct either the cystic or the common bile ducts. The most common symptom is abdominal pain, which may be due to inflammation of the gall bladder (cholecystitis), bile duct obstruction (biliary colic), or inflammation of the pancreas (pancreatitis). Partial obstruction of the common bile duct by a gallstone is the commonest cause of cholangitis (inflammation of the bile ducts), marked by the appearance of ‘Charcot's triad’ of abdominal pain, fever, and jaundice (named after the Parisian professor who described ‘biliary fever’ in 1876, although he was mainly famed as a neurologist).

‘Acalculous’ cholecystitis, in which gall bladder inflammation occurs in the absence of gallstones, accounts for about 10% of all cases of acute cholecystitis and also a proportion of those with chronic gall bladder inflammation. Gall bladder inflammation may occur during the course of typhoid fever. In a minority of cases, the responsible bacterium, Salmonella typhi, even persists in the gall bladder after the acute illness has resolved, and is intermittently excreted in the faeces. After a year, about 2–5% of individuals still excrete this organism and some, mostly females, continue to do so indefinitely. These ‘chronic carriers’ may spread the infection to others if their personal hygiene is careless, by the faecal–oral route. The most notorious carrier was ‘typhoid Mary’ who, in her capacity as cook to many households and institutions in the early 1900s, left a trail of typhoid victims across the US and Canada.

Stephen M. Riordan, and Roger Williams

See also alimentary system; bile; jaundice; liver.