People who run long distances (marathons, triathalons, endurance sports) may develop gastrointestinal blood loss.
(1) blood in the stools
(1a) melena (black and tarry stool)
(1b) hematochezia (blood in stool)
(1c) occult blood (Guiac or Gastroccult positive)
(2) abdominal pain
(3) anemia, which may be iron-deficiency related
(4) diarrhea (which may also occur independent of blood loss)
Possible causes for the blood loss:
(1) ischemic enterocolitis associated with decreased splanchnic perfusion
(2) repetitive trauma (cecal slap/flap syndrome indicates repeated impacts of the cecum against anterior abdominal wall)
Endoscopy shows hemorrhagic mucosal erosions either localized or diffuse in the colon. Some patients have lesions predominantly in the sigmoid colon . Other patients have lesions limited to the cecum and ascending colon.
(1) strenuous exertion
(2) aspirin ingestion or other medications associated with GI blood loss
(3) heat stress and/or dehydration
Differential diagnosis for GI blood loss:
(1) peptic ulcers
(4) inflammatory bowel disease
Differential diagnosis for anemia:
(1) march hemoglobinuria or runner's anemia
(2) iron deficiency
(3) vitamin deficiency
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Specialty: Surgery, orthopedic