Causes of gallstones

It is thought that gallstones develop because of an imbalance in the chemical make-up of bile inside the gallbladder. Bile is a liquid that is produced by the liver to help digest fats.

It is still unclear what leads to this imbalance, but it is known that gallstones can form in two ways:

  • there are unusually high levels of cholesterol inside the gallbladder and the excess cholesterol gradually solidifies to form a stone; four out of five gallstones are made up of cholesterol
  • there are unusually high levels of bilirubin inside the gallbladder; bilirubin is a waste product produced when red blood cells are broken down – the remaining one out of five gallstones is made up of bilirubin

Who’s at risk?

Gallstones are more common in the following groups:

  • women, particularly those that have had multiple pregnancies
  • obese people – people who are overweight with a body mass index (BMI) of 30 or above
  • people who are 40 years of age or over (the older you are, the more likely you are to develop gallstones)
  • people with cirrhosis (scarring of the liver)
  • people with the digestive disorders Crohn’s disease and irritable bowel syndrome (IBS)
  • people with a family history of gallstones (around a third of people with gallstones have a close family member who has also had gallstones)
  • people who have recently lost weight, either as a result of dieting or weight-loss surgery such as gastric banding
  • people who are taking a medication called ceftriaxone, which is an antibiotic used to treat a range of infections, including pneumoniameningitis and gonorrhoea

Women who are taking the combined oral contraceptive pill or undergoing high-dose oestrogen therapy (which is sometimes used to treat osteoporosisbreast cancer and the menopause) also have an increased risk of developing gallstones.

Other possible risk factors

Having type 2 diabetes and a lack of exercise are also possible risk factors.  However, they have not yet been conclusively proven to increase the risk of developing gallbladder problems. 

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