Document Type

Conference Proceeding

Publication Date

5-2-2025

Abstract

Gastrointestinal bleeding (GIB) is a recognized complication of endurance sports, particularly long-distance running. While most cases are mild and self-limited, studies indicate that up to 12% of ultramarathon participants experience occult bleeding. Severe or life-threatening GIB, such as ischemic colitis requiring surgery, has been reported but remains rare. Despite its potential significance, exercise-induced GIB remains poorly understood, with limited organized data on its prevalence and mechanisms. A 38-year-old male presented with a three-day history of melena following a recent marathon. Symptoms began with loose stools, progressing to tarry stools, accompanied by fatigue, exertional dyspnea, dizziness, and mild generalized abdominal discomfort. He denied hematemesis, bright red blood per rectum, or dietary changes. A prior GI workup in 2018 for hematochezia and IDA was unremarkable, including EGD, colonoscopy, capsule endoscopy, and CT enterography. His medical history was otherwise unremarkable, and NSAID use was minimal (4–5 times/month). On presentation, he was hemodynamically stable but pale. Labs revealed normocytic anemia with Hb 6.6 g/dL (baseline 14), Hct 26.9%, MCV 97.8 fL, and reticulocytosis. Iron studies showed ferritin 18 ng/mL, serum iron 44 mcg/dL, TIBC 366 mcg/dL, and transferrin saturation 12%. B12 and folate were normal, as were coagulation studies (PT 11.1 s, INR 1.1, fibrinogen 210 mg/dL). Peripheral smear showed no hemolysis, and flow cytometry ruled out PNH and lymphoma. He received IV PPIs and one unit of PRBCs, raising Hb to 7.4 g/dL. EGD and colonoscopy revealed no significant pathology except for grade 2 hemorrhoids. TTE and TEE showed moderate-to-severe AR, trileaflet aortic valve with calcification, and no stenosis. Cardiac MRI confirmed LV dilation (EF 55%) and moderate-to-severe AR. Capsule endoscopy was normal without any localized sources of bleeding. The patient underwent minimally invasive AVR and was discharged on daily PPIs. Further episodes of melena remain to be seen. Endurance running stresses the GI tract through splanchnic vasoconstriction, diverting up to 80% of blood flow to muscles and causing ischemic injury. Dehydration, with plasma volume losses of 10%–15%, worsens hypoperfusion, while repetitive impact induces microtrauma in the bowel. In this case, moderate-to-severe AR may have further contributed to ischemic vulnerability, though its role is less established than AS, making endurance running the most plausible diagnosis. Diagnosing exercise-induced GIB is challenging, especially in acute cases, as most data focus on occult bleeding. This patient’s workup failed to identify a source, reflecting the limitations of these modalities for transient lesions. The intermittent nature of ischemic or exercise-induced injury makes small bowel ischemia or angiodysplasia a plausible etiology in this context. Preventing GIB in endurance athletes involves optimizing hydration, pre-event nutrition, and selective PPI use, which can reduce stool occult blood positivity from 34% to 10%. Gradual training and monitoring for IDA symptoms are crucial, especially in athletes with underlying conditions. This case highlights the importance of recognizing exercise-induced GIB as a potential cause of anemia or acute bleeding in endurance athletes. As participation in endurance sports grows globally, understanding and addressing this condition will be critical to supporting safe and healthy athletic performance.

Comments

American College of Physicians Michigan Chapter and Society of Hospital Medicine Michigan Chapter Resident and Medical Student Day, May 2, 2025, Troy, MI

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