The gallbladder is a small pouch-like organ found underneath the liver. Its main purpose is to store and concentrate bile.
Bile is a liquid produced by the liver to help digest fats. It's passed from the liver into the gallbladder through a series of channels known as bile ducts.
The bile is stored in the gallbladder and, over time, becomes more concentrated, which makes it better at digesting fats.
The gallbladder releases bile into the digestive system when it's needed.
Gallstones are thought to develop because of an imbalance in the chemical make-up of bile inside the gallbladder.
In most cases the levels of cholesterol in bile become too high and the excess cholesterol forms into stones.
Gallstones are very common. It's estimated more than 1 in every 10 adults in the UK has gallstones, although only a minority of people develop symptoms.
You're more at risk of developing gallstones if you're:
Treatment is usually only necessary if gallstones are causing:
In these cases, keyhole surgery to remove the gallbladder may be recommended.
This procedure, known as a laparoscopic cholecystectomy, is relatively simple to perform and has a low risk of complications.
It's possible to lead a normal life without a gallbladder.
Your liver will still produce bile to digest food, but the bile will drip continuously into the small intestine, rather than build up in the gallbladder.
Gallstone disease is usually easily treated with surgery.
Very severe cases can be life threatening, particularly in people who are already in poor health.
But deaths from gallstone disease are rare in the UK.