What Causes Gallstones?

The liver produces a green-brown liquid that consists of fatty compounds, bile salts, cholesterol and other chemicals. This liquid (known as bile) is concentrated and passed on to the gall bladder for storage until foods (particularly fats) stimulate its release into the duodenum through the cystic duct and into the common bile duct. Occasionally, the bile in the gall bladder can become chemically unbalanced, which can cause hardened particles to form, eventually growing into stones.

Reasons for Gallstone Formation

There are a number of factors that can contribute to the formation of gallstones; these include:

Too Much Cholesterol in the Bile

The bile normally contains enough bile salts to dissolve the cholesterol that is excreted by the liver. However, if for some reason the cholesterol cannot be dissolved completely, the excess may form into crystals and eventually into stones. Excessive cholesterol may be due to a diet that is high in refined dietary carbohydrates (for example, white bread), high in cholesterol and low in fibre. The use of oral contraceptives can also raise cholesterol levels, as the genetic disorder known as hypercholesterolaemia.

Incomplete Emptying of the Gallbladder

Incomplete and infrequent emptying of the gallbladder may cause the bile to become overconcentrated and contribute to gallstone formation. Skipping meals, eating too little fat can cause the gallbladder to make fewer contractions, thus preventing it from emptying frequently or completely. Increased oestrogen levels as a result of pregnancy, hormone therapy or contraceptive pills may also decrease gallbladder movement.

Types of Gallstone

There are two major forms of gallstones: cholesterol stones and pigment stones.

Cholesterol stones are the most common type of gallstone, comprising 80% of gallstones in individuals from Europe and the Americas. They are green, yellow or white in colour and are composed of undissolved cholesterol, calcium and bilirubin (the residue from the breakdown of red blood cells).

Pigment gallstones are small, dark brown or black stones formed when the bile contains an excess of bilirubin. Although pigment gallstones are found in only 15% of cases from Europe and the Americas, in Southeast Asia they are more common than cholesterol gallstones.