Clinical Challenges

What is your diagnosis? - October 2019

A 28-year-old woman with a history of mild iron-deficiency anemia presented with acute onset of lower abdominal pain and bloody bowel movements. The patient reported actively training for a marathon and on the day of presentation she ran approximately 20 miles before developing acute sharp, crampy lower abdominal pain. This discomfort forced her to stop her run early and she subsequently had several loose bowel movements streaked with bright red blood that prompted evaluation.

In the emergency department, she was afebrile and hemodynamically stable with physical examination revealing slight tenderness to palpation in the left upper quadrant of her abdomen. Laboratory results were significant for mild leukocytosis (white blood cell count, 16.1 × 103/microL), anemia (hemoglobin, 10.3 g/dL), and iron deficiency (ferritin, 14 ng/mL; iron, 11 microg/dL; and iron saturation, 2%). Of note, lactate, erythrocyte sedimentation rate, and C-reactive protein levels were all within normal limits.
A computed tomography scan of her abdomen and pelvis demonstrated diffuse inflammation involving her colon and terminal ileum (Figure A).
The patient underwent a colonoscopy that revealed congested and dusky mucosa in the distal descending colon and throughout the transverse colon (Figure B). Biopsies of the affected areas were performed (Figure C). What is the diagnosis?


Exercise-induced acute ischemic colitis or “runner’s colitis”

Biopsies of the abnormal mucosa noted on colonoscopy revealed mucosal necrosis with stromal hyalinization, crypt atrophy, and acute inflammation (Figure C), consistent with a diagnosis of exercise-induced acute ischemic colitis. Exercise-induced ischemic colitis, sometimes referred to colloquially as “runner’s colitis,” is a rare but well-documented complication of long distance running.1

A number of physiologic changes occur in the human body during prolonged exercise, including redirection of blood flow from the gut to exercising muscles. Although this process usually serves to better manage available oxygen and nutrients during times of stress, it can occasionally result in unfavorable outcomes as depicted herein. During exercise, the increased sympathetic tone influences rerouting blood with some studies demonstrating up to 80% reduction in splanchnic blood flow with prolonged exercise.2 In addition, the transient hypovolemia many runners experience if they do not remain adequately hydrated can impair mesenteric perfusion. The splenic flexure of the colon and the rectosigmoid junction are particularly prone to ischemic injury in these settings, given the “watershed” nature of their blood supply.

An extensive review of published cases revealed the reversible nature of this ailment, as all but one subject, who required subtotal colectomy for colonic perforation, had resolution of ischemia on repeat evaluation.3 The patient had a follow-up computed tomography angiogram 2 months after discharge that revealed unremarkable mesenteric vasculature and resolution of the previously seen colonic wall thickening and pericolonic fat stranding.


1. Buckman MT. Gastrointestinal bleeding in long-distance runners. Ann Intern Med. 1984;101:127-8.

2. Qamar MI, Read AE. Effects of exercise on mesenteric blood flow in man. Gut.1987;28:583-7.

3. Beaumont AC, Teare JP. Subtotal colectomy following marathon running in a female patient. J R Soc Med, 1991;84:439-40.

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