Inflamed gall bladder. Light micrograph (LM) of a section through a gall bladder with cholecystitis (inflammation). The mucosa lining (purple) is thickened. The majority of cases of cholecystitis are caused by gall stones blocking the outlet to the bile duct. The build up of bile causes chemical irritation to the gall bladder and causes it to swell. It may also become infected with bacteria from the digestive system. Treatment is usually with removal of the gall bladder. Magnification: x30 when printed at 10 centimetres wide.