Inflammation of the gall bladder, which collects bile from the liver and releases it into the duodenum. Almost always a complication of a gallstone, it can be acute, with severe pain, or chronic, with nagging pain. The acute form is caused by a gallstone blocking the exit from the gall bladder, leading to increased pressure, swelling and colicky pain. Sometimes the stone returns into the bladder, in which case the symptoms disappear. Characteristic symptoms of the acute condition are sudden violent and continuous pain in the upper abdomen, often associated with nausea and vomiting, and usually also fever. Important complications are perforation of the gall bladder followed by peritonitis, or an abscess in the gall bladder. The stone can also enter the bile duct, blocking the flow of bile from the liver and causing severe jaundice. Diagnosis is by reference to the clinical picture and patient’s history, supplemented by blood tests. Gallstones seldom show on a normal X-ray; the swollen gall bladder can sometimes be detected by physical examination. Treatment is by removal of the gall bladder and stone. The operation may be performed immediately, or after a ‘cooling-off period’; it is simpler if the gall bladder has calmed down. In the meantime treatment is with painkillers, feeding by infusion, and possibly antibiotics. If complications threaten the operation must be performed immediately.