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Exercise-Induced Diarrhea

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Ovid: 5-Minute Sports Medicine Consult, The


Exercise-Induced Diarrhea
Kimberly Harmon
Basics
Description
  • Increased stool frequency or volume often accompanied by lower abdominal cramping, or urge to defecate associated with strenuous physical activity:
    • Normal physical examination
    • Normal laboratory and diagnostic studies
  • Synonym(s): Runner's diarrhea; Runner's trots
Epidemiology
  • Primarily associated with running sports, but also common in cycling and reported in swimming, wrestling (1,2,3)
  • Difficulty with existing research:
    • Difficult to control all variables (diet, exercise intensity, underlying pathology such as irritable bowel syndrome)
    • Studies often lack a denominator, making a true incidence of symptoms difficult to determine.
    • Many studies are surveys with low response rates, which introduces a selection bias.
    • Subject's dietary recall often is inaccurate.
Prevalence
  • Prevalence of diarrhea reported from 8–60% in athletes
  • Prevalence of diarrhea in control subjects reported up to 40%
Risk Factors
  • Underlying bowel pathology may worsen with strenuous exercise.
  • Dehydration
  • Occurs more frequently with increased exercise intensity
  • Occurs more frequently in untrained participants
  • Type of exercise (running > cycling, swimming, speed skating, cross-country skiing)
  • Meals rich in fat, protein, and fiber taken shortly before exercise worsen symptoms.
Etiology
Proposed mechanisms (1,2,3):
  • Mesenteric ischemia:
    • With strenuous exercise, blood is shifted away from the gut and to the working muscle.
    • Exercising at 70% VO2 max decreases blood flow to GI tract by 60–70%.
    • May lead to the production of endotoxin
    • Causes a cascade of inflammatory events that can further impair the mucosal integrity
    • Increased activity of the sympathetic nervous system leads to decreased sphlanic blood flow and is caused by:
      • Mental stress
      • Hyperthermia
      • Dehydration
      • Hypoglycemia
  • Increased sympathetic nervous system activity:
    • Suppresses parasympathetic activity
    • Decreased gut tone and resistance
    • Increased colonic transit times
    • Secretion of gastroenteropancreatic hormones
  • Mechanical stimulation of the colon due to intra-abdominal jostling
  • Enteric fluid and electrolyte balance
Diagnosis
History
  • Increased stool frequency or volume, or loose stools after exercise
  • Often accompanied by abdominal cramping and urge to defecate
  • May occur just with competition and not with training
  • Normal bowel function at other times
Physical Exam
  • Increased stool frequency
  • Increased stool volume
  • Loose or explosive stools
  • Urge to defecate, often necessitating the athlete to cease exercise
  • Abdominal cramping
  • Rectal bleeding
  • Unremarkable physical examination
Diagnostic Tests & Interpretation
  • Exercise-associated diarrhea is a diagnosis of exclusion.
  • Workup is used to rule out other causes of diarrhea.
Lab
  • Stool cultures, including Clostridium difficile
  • Consider antigliadin and tissue transaminase antibodies to rule out celiac sprue.
  • Thyroid-stimulating hormone
  • Consider stool osmolar gap if eating disorder and/or laxative abuse is suspected:
    • Increased osmotic gap is suspicious for laxative use.
Imaging
Imaging studies should be obtained as clinically indicated:
  • Consider barium enema
  • Contrast-enhanced CT scan
Diagnostic Procedures/Surgery
Diagnostic procedures such as sigmoidoscopy or colonoscopy may be considered as clinically indicated.

P.145


Differential Diagnosis
  • Irritable bowel disease
  • Inflammatory bowel disease
  • Infection
  • Colon cancer
  • Superior mesenteric or portal venous thrombosis
  • Malabsorption
  • Microscopic colitis
  • Laxative abuse
  • Lactose intolerance
  • Hyperthyroidism
Treatment
  • Treatment is generally conservative and should include (1,2,3)[C]:
    • Training modification:
      • Increase volume and intensity of training slowly.
    • Try to evacuate prior to exercise.
    • Diet modification
  • Acute symptoms usually rapidly resolve with cessation of activity:
    • Hyoscyamine (Levsin) 0.125 mg sublingually sometimes is helpful in stopping abdominal cramping after exercise.
Medication
All athletes should consult with the governing bodies of their sports regarding banned substances.
First Line
  • Antispasmodics may be helpful, but have anticholinergic side effects and should be used with caution:
    • Dicyclomine (Bentyl) 20 mg PO q.i.d.
    • Hyoscyamine (Levsin) 0.125–0.25 mg PO/s.l. q4h PRN:
      • The athlete should remain well hydrated.
      • Use in hot/humid conditions is not ideal
  • Loperamide (Imodium) decreases intestinal motility and affects water and electrolyte absorption:
    • Loperamide 2–4 mg 30 min before exercise
    • Side effects are rare.
Second Line
  • Opiate/atropine combinations (diphenoxylate [Lomotil]) should be used with caution:
    • Opiates are habit-forming.
    • May be banned depending on governing body of the sport
    • May adversely affect performance
  • Atropine may cause hyperthermia, tachycardia, and heat regulation problems.
Ongoing Care
Diet
Dietary modification can be helpful (1,2,3)[C]:
  • Stay well hydrated.
  • Avoid caffeine, which is both a diuretic and a cathartic.
  • Avoid foods that exacerbate symptoms (eg, lactose in lactose-intolerant athlete).
  • Limit intake of gas-forming foods (broccoli, onions, beans).
  • Eat a small, low-fat, low-fiber meal several hours before competition:
    • Use low-osmolar sports drink between meal and competition or training.
  • Avoid large doses of vitamin C, sodium bicarbonate, and carbohydrate drink prior to exercise.
  • If athlete still has difficulty with diarrhea or urge to defecate, try complete nutritional liquid that is low in fiber during the day preceding competition.
Prognosis
Most athletes can learn how to manage their symptoms through the use of diet and training.
References
1. Casey E, Mistry DJ, MacKnight JM. Training room management of medical conditions: sports gastroenterology. Clin Sports Med. 2005;24:525–540, viii.
2. Ho GW. Lower gastrointestinal distress in endurance athletes. Curr Sports Med Rep. 2009;8:85–91.
3. Simons SM, Kennedy RG. Gastrointestinal problems in runners. Curr Sports Med Rep. 2004;3:112–116.
Additional Reading
Green GA. Gastrointestinal disorders in the athlete. Clin Sports Med. 1992;11:453–470.
Swain RA. Exercise-induced diarrhea: when to wonder. Med Sci Sports Exerc. 1994;26:523–526.
Codes
ICD9
  • 306.4 Gastrointestinal malfunction arising from mental factors
  • 564.5 Functional diarrhea
  • 787.91 Diarrhea


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