Gastrointestinal and liver disorders are often observed in high performance athletes, especially those training for the increasingly popular endurance sports including the marathon and the triathlon. The disorders often start with stress before competition or training, followed by dehydration during the event. Insufficient training is an aggravating factor as are certain environmental factors including hot climate, irregular terrain and high altitude. Athletes may also consume non-steroid anti-inflammatory drugs, for example after a minor bone lesion or joint sprain, in an attempt to maintain their highest level of performance. Gastric signs include epigastric pain known to be caused by ischaemic gastritis resulting from decreased splanchnic flow and increased vasoconstriction in the gastric mucosa. Gastrooesophageal reflux results from modifications in sphincter tone and gastric emptying. Drinking hyperosmolar liquids also plays a role. Abdominal pain, diarrhoea, melena and uncommonly ischaemic colitis are the main signs of colic disorders. Mesenteric ischaemia may occur due to lowered splanchnic blood supply (by as much as 80% in some cases). Mechanical trauma is another mechanism; in marathon runners the "caecal slap syndrome" is a repeated microtrauma of the caecum against a hypertrophied muscular wall. Waterborne infectious agents may also lead to colic lesions. Exertion heat stroke is an emergency situation which can cause multiple organ damage and usually occurs after long intense exercise, often, but not always in a hot environment. Uncompensated thermogenesis and excessive loss of water by perspiration leads to central hyperthermia and ischaemic hepatic necrosis. Fatal liver failure has been observed. More or less severe symptoms of gastrointestinal or hepatic disorders are observed in 30% of high performance athletes and the incidence may reach 40% in those who have trained insufficiently. Such disorders lead to reduced performance in 10% of these athletes.