Bile contains water, cholesterol, fats, bile salts (natural detergents which break up fats) and bilirubin. This latter is a pigment which gives the bile itself, and our stools, colour.

Normally, most of the bile released into the small intestine is recirculated by being absorbed in the intestine and returned to the liver in the blood stream.

What are gallstones?

Gallstones are solids which can form in the gallbladder. They are made up of cholesterol and bile pigments which solidify into crystalline particles. Eighty percent are made of cholesterol, and are usually white or yellow. The other 20 percent are pigments stones formed from bilirubin and calcium salts found in bile.

These stones are of variable size and may number into the thousands, or may form one large stone.

Why do gallstones form?

Gallstones seem to form in response to a number of factors, including body chemistry, body weight, gallbladder motility and perhaps diet.

Cholesterol gallstones form when the bile contains an abnormally high proportion of cholesterol in relation to bile salts. In addition to this infrequent or incomplete emptying of the gallbladder may result in overconcentrated bile, and the bile may contain proteins which promote or inhibit cholesterol crystallisation into gallstones.

Obesity is a major risk factor for the formation of gallstones, probably because obese people tend to have large amounts of cholesterol in their bile, low levels of bile salts and inadequate gallbladder emptying.

Increased oestrogen levels also seem to play a part in gallstone formation, probably by increasing cholesterol levels in the bile and decreasing gallbladder movement and emptying.

Prolonged fasting and very low calorie diets also seem to promote the formation of gallstones.

The relationship between gallstones and diet is not clear, but their formation may be favoured by a low fibre, high fat diet.

Who gets gallstones?

Women are twice as likely as men to get gallstones, and tend to get them between the ages of 20 and 60. Both men and women over the age of 60 have a higher chance of developing gallstones than they do at a younger age.

Pregnant women, and those using the oral contraceptive pill or hormone replacement therapy are at risk of developing gallstones.

You have a higher risk of developing gallstones if you are overweight, and also paradoxically if you are trying to lose weight very fast by crash dieting — never a good idea anyway!

What are the symptoms of gallstones?

The vast majority of people who have gallstones don't even realise that they have them — so-called silent stones. These are usually detected by accident during an abdominal X-ray for something else.

Some people, women in particular, who have problems with heartburn and reflux land up having gallstones discovered on X-ray, which are then assumed to be causing the problems, and removed, with little or no change in their symptoms.

Complications caused by gallstones

Gallstones cause complications if they move and block the ducts through which the bile passes. This obstruction can occur with or without infection. Obstruction leads to pain in the upper abdomen, the back between the shoulder blades or the right shoulder, and may be accompanied by nausea and vomiting. Jaundice occurs in some cases.

One of the more common complications is cholecystitis, in which the cystic duct, the channel through which bile flows from the gallbladder to the small intestine, becomes blocked. This causes inflammation of the gallbladder, with pain and fever.

Pancreatitis (inflammation of the pancreas) can also be caused by gallstones blocking the flow of digestive fluids between the pancreas and the small intestine.

The duct between the liver and the small intestine becomes blocked less commonly, but is a serious complication, and results in pain and jaundice.

If any of these ducts are blocked for any length of time, damage can occur to the liver, pancreas or gallbladder.

How are gallstones diagnosed?

Gallstones are often picked up on abdominal X-ray for something else. If a specific diagnosis of gallstones is being sought due to symptoms, then ultrasound is often used.

How are gallstones treated?

Cholecystectomy, removal of the gallbladder, is the most common method of treatment. Until recently this tended to be done through a large incision into the abdomen, requiring up to a week in hospital afterwards. More recently, so-called keyhole, laparoscopic, surgery is used, in which the gallbladder is removed after several small holes have been made in the abdomen to allow surgical instruments and a video camera to be inserted. This technique is much less invasive and the patient generally requires a lot less time in hospital.

Oral therapy designed to dissolve the gall stones is generally confined to cholesterol stones, and is reserved for special situations, for example people who cannot tolerate surgery.

In about half the cases who are treated this way the gallstones recur because the gallbladder is left intact.