Gallstones

The gallbladder

The gallbladder is a small, pear-shaped pouch about three to six inches long. It is tucked just under the liver, below the right rib cage and is connected to the intestine and liver by small tubes called bile ducts.

Bile ducts carry bile, a yellow-green fluid produced by your liver. Bile contains water, cholesterol, phospholipids and chemicals to aid digestion (bile acids), as well as waste products for excretion via the bowel, such as bilirubin^1,2,3.

Bile is collected and stored in the gallbladder, and released along the bile ducts into the intestine when we eat food¹. It plays a central role in helping the body digest fat. Bile acts as a detergent, breaking up the fat from food in your gut into very small droplets, so that it can be absorbed. It also makes it possible for your body to take up the fat-soluble vitamins A, D, E and K from the food passing through your gut.

What are gallstones?

Gallstones are lumps of solid material that form in the gallbladder. They usually look like small stones or gravel, but can be as small as sand or as large as pebbles, sometimes filling the gallbladder. They may take years to grow and there may be one or several.

Gallstones are formed from the chemicals in bile and may be:

• pure cholesterol stones – these are the most common type of stone and are made up of cholesterol, which is a type of fat
• pure pigment stones – these consist of calcium and bilirubin (a pigment from broken down red blood cells) which have solidified 
• mixed stones – these are a combination of cholesterol and pigment stones ⁴.

Most people with gallstones have no symptoms. In some people (between one and four out of 100) the stones begin to cause trouble by blocking the flow of bile and causing inflammation. Gallstones can leave the gallbladder and cause other complications such as blocking the bile duct, causing jaundice, or blocking the opening to the pancreas, causing pancreatic inflammation (pancreatitis).

If complications arise, a surgical procedure may be required to remove the gallbladder. While the gallbladder is useful, it is not essential. You can safely have your gallbladder removed without it interfering with your ability to digest food¹, as often, by the time gallstones have developed, the gallbladder is no longer functioning properly.

What causes gallstones?

Gallstones are formed when the different elements which make up your bile (see ‘The gallbladder’) become imbalanced. Cholesterol stones form when cholesterol levels in your bile are much greater than your bile acid levels, this causes the cholesterol in your bile to solidify³.

There is evidence that dietary factors, such as diets high in cholesterol, saturated fat, refined sugar and low in fibre, increase the risk of developing cholesterol gallstones ^3,5,6.

Gallstones are more common in women than in men, especially during women’s fertile years and during pregnancy. This is because cholesterol is a component of oestrogen, and at these times fluctuating levels of oestrogen need to be broken down to cholesterol and excreted in bile.

Pigment stones may form when the amount of bilirubin in bile is excessive. This can occur in conditions such as sickle cell disease^3,7.

Gallstones can also form when the flow of bile is reduced. This may occur due to:

• damage to the liver (cirrhosis) or damage to the biliary tract which affects the secretion and flow of bile³  
• long periods of fasting during which there is less requirement for bile, leading to bile stasis (decreased flow of bile)⁸.

Who is most likely to get gallstones?

Gallstones are very common. About one in four women and one in eight men⁹ develop gallstones at some stage in their life. Not everyone with high cholesterol levels in their bile develops gallstones, it is not fully understood why some people have them and others don't³. However, there are known risk factors that are thought to increase the development of gallstones. Research shows that gallstones are more common in the following groups of people: ^1,4

• overweight women and men
• women who have been pregnant or who are taking an oral contraceptive
• women who are undergoing high-dose oestrogen therapy (which is sometimes used to treat osteoporosis, breast cancer and the menopause)
• people with digestive disorders such as Crohn’s disease or irritable bowel syndrome (IBS), or metabolic syndromes¹
• people who have recently lost weight either as a result of dieting or weight-loss surgery, such as gastric banding
• people aged 40 years and older
• people with a family history of gallstones
• people with cirrhosis (scarring of the liver)
• people with conditions affecting the flow of bile, such as primary sclerosing cholangitis^10,11, primary biliary cirrhosis^3,12 and obstetric cholestasis^13,14
• people who have had a previous upper abdominal operation.

What are the effects of gallstones?

Asymptomatic gallstones
Many people live with gallstones without symptoms and are unaware they have them until the stones show up in tests performed for another reason¹⁴. This is called asymptomatic gallstones.

Uncomplicated gallstones
The smaller the stone, the more able it is to travel about within the gallbladder. Symptoms may develop because the stones have temporarily blocked the opening to the gallbladder (the cystic duct). This usually leads to sudden (acute) attacks of abdominal pain; it may be several weeks or months in between each attack. This is called uncomplicated gallstones and attacks are often referred to as biliary colic. Over time, this may lead to chronic inflammation and scarring of the cystic duct, known as chronic cholecystitis. 

Complicated gallstones
Gallstones can sometimes block the gallbladder exit (cystic duct), causing pain and inflammation of the gallbladder if the blockage lasts for a long time. Gallstones can also leave the gallbladder and cause more severe problems in the bile duct or the pancreas. These are called complicated gallstones and include the following:⁴ 

• Acute cholecystitis (inflammation of the gallbladder) – a blockage in the cystic duct causes the gallbladder to become swollen, irritated and inflamed.
• Acute cholangitis (inflammation of the bile ducts) – which occurs when the flow of bile from the liver is blocked and the bile becomes infected.
• Acute pancreatitis (inflammation of the pancreas) – when stones pass from the bile duct into the exit of the pancreatic duct causing a temporary obstruction to the flow of digestive juices from the pancreas, resulting in inflammation.
• Gallstone ileus (bowel obstruction) – when large gallstones become lodged in the duodenum or other parts of the small bowel¹⁵. 

Complicated gallstones can lead to other long term gallbladder complications such as chronic inflammation and scarring due to frequent and severe attacks, known as chronic cholecystitis³.

Chronic inflammation of the bile ducts and gallbladder can increase your risk of bile duct cancer (cholangiocarcinoma)¹⁶ and gallbladder cancer. However, people with a history of gallstones have less than 1 in 10,000 chance of developing gallbladder cancer¹. For more information on bile duct cancer, please see our Liver cancer publication.