Occult bleeding, haematochezia and the endurance athlete: what are the risks?

Roy J. Shephard


Objective. To examine the risks of visceral ischaemia associated with participation in endurance sport, including gastro-intestinal bleeding and systemic endotoxaemia.

Methods. A systematic search of the Ovid/Medline data-base from January 1996 to May 2015, combining the terms ischaemia/visceral ischaemia/gastro-intestinal haemorrhage/bleeding/ and endotoxins with exercise/endurance exercise/physical endurance/marathon/ultra-marathon/triathlon, supplemented by a review of reference lists and personal files.

Results. Around 20% of participants in marathons and other endurance events develop objective manifestations of visceral ischaemia in the first 2 days following a race, usually occult gastro-intestinal bleeding. A small proportion of athnletes develop overt bleeding. This generally resolves over a few days, although there are 2 reported cases that required a partial colectomy, and 1 reported death. In some individuals, plasma levels of bacterial endotoxins may also rise.

Conclusions. Once other more dangerous diagnoses have been excluded, the blood loss associated with exercise-induced visceral ischaemia can usually be treated expectantly. A watch must be kept for anaemia secondary to repeated blood loss, but the risks of bleeding requiring colectomy and bacterial sepsis seem too small either to require other specific treatment or to influence clinical advice on the wisdom of participating in ultra-endurance events.


Athletic anaemia; Colonic ischaemia; Endotoxins; Endurance exercise; Gastro-intestinal bleeding; Marathon; Risks of exercise; Triathlon; Ultramarathon; Visceral blood flow

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ISSN: 19206216