The gall bladder lies on the under side of the liver, at the top of the belly, on the right hand side of the body. It is at a level just below the nipple, behind the front of the rib cage.

The gall bladder is a pear-shaped sac about 8 to 10 cm (2 ½ to 3 ½ inches) long. At its narrow end it leads into a tube called the cystic duct. The gall bladder stores and concentrates bile. The bile is made in the liver and flows into, and out of, the gallbladder through the cystic duct.

The cystic duct is a tube about 4cm (1 ½ inches) long. It joins the tube draining bile from the liver (the common hepatic duct) to form the common bile duct. The common bile duct then empties into the duodenum, the first part of the small bowel (small intestine) just beyond the stomach.

Bile is important for two reasons:

• salts in the bile help the body to digest fatty food
• the bile removes some waste products from the body, in particular bilirubin, which is the end product of the breakdown of worn out red blood cells, and which gives the bile is dark green colour.

When fatty food enters the duodenum from the stomach a hormone is released that causes the gall bladder to contract. This squeezes bile from the gall bladder, through the cystic duct and common bile duct, into the duodenum.

Once it is in the duodenum the bile salts break up fat in the food, and the waste products in the bile, like bilirubin, pass through the bowel to form part of the faeces and are removed from the body.