Exercise-related gastrointestinal disorders

INTRODUCTION — Exercise-related gastrointestinal (GI) symptoms can impact performance. Many of these symptoms are related to physiologic changes resulting from exercise [1,2]. Physiologic changes include alterations in enteric nervous system activity, circulating gut hormone levels, intestinal blood flow, nutrient and electrolyte absorption, intestinal secretion and permeability, as well as motility [1,3]. The term "exercise-induced gastrointestinal syndrome" has been used to describe these complex responses to exercise that affect and compromise normal GI function and integrity [4]. This topic review will discuss the most frequently observed GI disorders that occur in athletes and active individuals.

EPIDEMIOLOGY AND RISK FACTORS — The incidence of exercise-induced GI symptoms range from 20 to 96 percent [5-12]. The incidence is higher in females and in younger athletes [2,5]. Exercise-related GI symptoms are frequently associated with consumption of a meal within two to three hours of exercising [5,7,13-16]. Dehydration and analgesic use are associated with a higher incidence of GI symptoms [17,18]. While some studies have found an association between the intensity of the exercise and the incidence of GI symptoms, results have been inconsistent [5,7,14,15,19,20].

GI symptoms vary with the type of exercise. In general, long-distance runners have a high incidence of lower GI symptoms (eg, fecal urgency, diarrhea, rectal bleeding, bloating, flatulence), and transient abdominal pain. Cyclists have a high incidence of upper GI symptoms (eg, regurgitation, heartburn, nausea, and vomiting) [4,5,7,14,16,21]. Nausea is the most frequently reported symptom in ultramarathon runners [11,22,23].

ABDOMINAL PAIN

Exercise-related transient abdominal pain — Exercise-related transient abdominal pain (ETAP) (side-stitch, stitch, or sub-costal pain) is a frequent cause of mild abdominal pain in athletes.

●Incidence – The incidence of ETAP ranges from 6 to 68 percent [5-7,14,15,24,25]. ETAP occurs most frequently during long-distance running but has also been associated with other sports [24]. The incidence is higher in younger individuals and following recent ingestion of food and hypertonic fluids.

●Pathogenesis – Proposed pathophysiologic mechanisms include diaphragmatic ischemia, jolting stress on subdiaphragmatic ligaments supporting the abdominal viscera, and frictional irritation of the parietal peritoneum [24,26,27]. Distension of the stomach and gut by food ingestion or repetitive movement of the torso can exacerbate peritoneal irritation [28].

●Clinical manifestations and diagnosis – ETAP is often described as a sharp or stabbing pain, cramping, aching, or pulling in the abdomen [24]. The pain is usually well-localized to the right (46 percent) and left (23 percent) subcostal regions but can occur in other parts of the abdomen [29]. A presumptive diagnosis of ETAP can be made in patients with transient, mild, well-localized abdominal pain that occurs in the setting of exercise and is relieved with cessation of physical activity. Patients with severe abdominal pain or persistent abdominal pain after cessation of exercise require evaluation for other causes of abdominal pain. (See "Evaluation of the adult with abdominal pain".)

●Management and prevention – Cessation of exercise remains the most effective means of relieving ETAP. Other physical maneuvers that have demonstrated some efficacy in small studies, including modified expiration through pursed lips after deep inhalation, wearing a tightened abdominal belt, contraction of abdominal muscles by leaning forward while running, and pushing on the site of pain [24,30]. General measures to prevent ETAP include avoidance of food and fluid intake at least two hours prior to exercise [7,15,24,27]. While a gluten-free diet is popular among over 40 percent of athletes without celiac disease, perceived benefits in symptoms and performance have not been supported in blinded studies [4]. A short-term (six to seven days) diet low in fermentable oligosaccharide, disaccharide, monosaccharide, and polyols (low fermentable oligo-, di-, and monosaccharides and polyols) may help reduce exercise-related GI symptoms and pain [4,31-33]. Milk products, meat, legumes, and high-fiber foods are often avoided by runners to minimize symptoms [34,35]. Patients with ETAP should be advised to consume frequent, small volumes of hypotonic fluids during exercise. Hypertonic solutions (eg, reconstituted fruit juices) should be avoided prior to and during exercise. Physical conditioning and more specifically, improved core stability, may prevent ETAP [24,27]. However, evidence to support specific regimens for physical conditioning and core stability are limited [36].

Intestinal ischemia

●Epidemiology – Exercise-induced intestinal ischemia is rare [37-40], but can occur even among young individuals or in those with risk factors (ie. iron deficiency anemia, cardiovascular disease) [41]. Mesenteric and colonic ischemia in the setting of exercise is typically nonocclusive. The ischemic segment most often involves the proximal colon but has also been described in the sigmoid colon and ileum [39,42,43]. The predilection for right-sided ischemic colitis is due to an increased susceptibility of these end arteries in low-flow states [39,40].

●Pathogenesis – Exercise-induced intestinal ischemia may be related to a decrease in mesenteric blood flow during exercise, which decreases between 50 and 80 percent [44-47]. For example, cycling for 60 minutes at 70 percent of capacity by healthy males was associated with reduced intestinal blood flow, leakage of gut-specific enzymes into plasma, and increased intestinal permeability, suggesting mild injury [48]. The reduction in splanchnic blood flow may be due to an exercise-induced reduced splanchnic artery diameter or resistive index and may be aggravated by exercise intensity, duration, transient exercise-induced dehydration, and higher environmental temperature [12]. However, correlation between alterations in physiologic mesenteric blood flow and intestinal ischemia in athletes has not been definitively demonstrated.

●Clinical manifestations and diagnosis – Patients may present with abdominal pain, bloating, nausea, or vomiting [12,40,42,46,49]. Rectal bleeding or bloody diarrhea usually develops within 24 hours. In contrast to ETAP, pain associated with intestinal ischemia is more severe, is not as well localized, and persists after cessation of exercise. The diagnostic evaluation of patients with ischemic colitis and mesenteric ischemia is discussed in detail separately. (See "Overview of intestinal ischemia in adults" and "Overview of intestinal ischemia in adults", section on 'Nonocclusive mesenteric ischemia' and "Colonic ischemia" and "Nonocclusive mesenteric ischemia".)

●Management and prevention – Most patients with exercise-induced ischemic colitis have complete resolution with supportive care and correction of hypovolemia. In rare cases, exercise-induced ischemic colitis may be severe and require surgical resection [37,38]. The management of ischemic colitis and mesenteric ischemia is discussed in detail separately. (See "Colonic ischemia" and "Chronic mesenteric ischemia" and "Nonocclusive mesenteric ischemia" and "Acute mesenteric arterial occlusion".)

Patients with exercise-induced intestinal ischemia should be counseled to maintain careful hydration prior to, during, and after exercise in order to maintain normal blood pressure for intestinal perfusion. Reduction in exercise intensity or duration should also be recommended, especially in those with cardiovascular disease or other risk factors for developing intestinal ischemia. The prevention of ischemic colitis and mesenteric ischemia is discussed in detail separately.

UPPER GASTROINTESTINAL SYMPTOMS

Gastroesophageal reflux

●Epidemiology – Heartburn and regurgitation are reported in 15 to 20 percent of athletes, a rate similar to that reported in the general population [5,6,14,16,25]. In patients with gastroesophageal reflux disease (GERD), studies report worsening of heartburn and/or increased reflux during exercise [50]. The incidence of GERD increases with the intensity of exercise [9,27,51-56]. Vigorous exercise can induce GERD in normal subjects especially if exercise is performed within one hour of a meal [51,53].

●Pathogenesis – Multiple factors are believed to contribute to the development of reflux in athletes [57]. These include exercise-induced increase in intra-gastric pressure due to contraction of abdominal musculature; delayed gastric emptying from reduced splanchnic blood flow and hypertonic fluids; impaired secretion of protective factors from the GI mucosa; decreased esophageal clearance from a reduction in the duration, frequency, and intensity of esophageal contraction; and an increase in the number of lower esophageal sphincter relaxations [51,55,56,58,59]. In one study, treatment of athletes with GERD symptoms with a proton pump inhibitor decreased exercise-induced acid reflux but did not significantly alter GERD symptoms, supporting the multifactorial etiology of reflux in athletes [60].

●Clinical manifestations and diagnosis – Symptoms of GERD include heartburn, regurgitation, and chest pain. The clinical manifestations and diagnosis of GERD are discussed in detail separately. (See "Clinical manifestations and diagnosis of gastroesophageal reflux in adults".)

●Management and prevention – Patients should be advised to avoid high-calorie, fatty meals three hours prior to exercise and hypertonic fluids during exercise [57]. The management of patients with GERD usually requires acid suppression with a histamine 2 receptor antagonist or proton pump inhibitor and is discussed in detail separately [60]. (See "Medical management of gastroesophageal reflux disease in adults".)

Nausea and vomiting

●Incidence – Nausea is reported in 6 to 26 percent of runners [5-7,14-16,25]. Approximately 2 to 6 percent of athletes report vomiting. However, under extreme conditions, the incidence of nausea and vomiting is higher.

●Pathogenesis – The etiology of exercise-induced nausea and vomiting may be similar to that of reflux in athletes, with exercise-induced delayed gastric emptying and altered intestinal motility contributing to symptoms [61]. Although gastric acidity is not significantly altered with exercise, increase in gastric bile acid levels may contribute to nausea [62,63]. Endotoxemia and compromised intestinal barrier function has also been implicated in the pathogenesis of nausea and may be increased following ingestion of carbohydrates during exercise [4,64,65].

●Clinical manifestations and diagnosis – Exercise-induced nausea and vomiting typically occur during or shortly after exercise. Symptoms are usually self-limited and rarely result in dehydration or electrolyte disturbances. In most cases, the diagnosis is made based on the clinical history and does not require additional testing. However, patients with frequent, severe, or persistent symptoms, and other associated symptoms (eg, abdominal pain, distension, feculent emesis, vertigo, headache, chest discomfort) require evaluation for alternative etiologies. An approach to the evaluation and management of nausea and vomiting is discussed in detail separately.(See "Approach to the adult with nausea and vomiting".)

●Management and prevention – Patients should be advised to avoid high-calorie, fatty meals three hours prior to exercising [6,66]. Limited data suggest that during endurance or intense exercise, carbohydrate intake predominantly in liquid form may be associated with fewer symptoms as compared with gels and bars [67,68]. The primary treatment for nausea and vomiting associated with exercise is the prompt cessation of physical activity. Anti-emetics such as ondansetron have not been shown to be effective in ultramarathon runners [69]. Management of nausea and vomiting and hypovolemia are discussed elsewhere. (See "Approach to the adult with nausea and vomiting", section on 'Treatment' and "Maintenance and replacement fluid therapy in adults" and "Treatment of severe hypovolemia or hypovolemic shock in adults".)

ACUTE DIARRHEA

Exercise-induced diarrhea — Diarrhea and the urge to defecate ("runner's trots") can often interrupt exercise.

●Incidence – The incidence of exercise-associated diarrhea ranges from 14 to 38 percent in long-distance runners while the urge to defecate during exercise ranges from 24 to 54 percent [5,6,14,16,25]. The incidence varies based on the intensity of exercise and is more frequently reported in women [5,7,16].

●Pathogenesis – The pathogenesis of exercise-induced diarrhea is unclear. It is hypothesized that mechanical stimulation of the intestinal mucosa results in the secretion of vasoactive intestinal peptide and prostaglandins with subsequent alterations in intestinal secretion [70-72]. Exercise-induced alterations in autonomic nervous system activity are thought to influence colonic and possibly small bowel motility [55]. Other possible mechanisms of diarrhea include an exercise-induced altered mucosal permeability which may be increased by concomitant nonsteroidal anti-inflammatory drug use [73-76]. Reduced carbohydrate and protein absorption during exercise have been observed in athletes, which may contribute to malabsorption [4].

●Clinical manifestations and diagnosis – Symptoms include urgency to defecate and diarrhea during exercise [5,6,14,16,25]. Fecal incontinence is rare and in one study was reported in 4 percent of individuals. Diarrhea may be provoked by pre-race anxiety, the proximity of the most recent meal, and the intensity of exercise [5,7,16].

Exercise-induced diarrhea is typically self-limited and rarely results in dehydration or electrolyte disturbances. Athletes with diarrheal symptoms lasting greater than 24 hours or concomitant symptoms of abdominal pain, fever, hematochezia, or vomiting should be evaluated for other potential etiologies. (See "Approach to the adult with acute diarrhea in resource-abundant settings", section on 'Evaluation' and 'Intestinal ischemia' above.)

●Management and prevention – Management is supportive and, based on the severity of symptoms, may require a reduction in exercise intensity or rest and hydration with oral or intravenous fluids. The mainstay of prevention of exercise-induced diarrhea includes the avoidance of fatty, high-caloric meals, or high-glycemic index foods three hours before exercising [66]. One study suggested a benefit from an elemental diet, consisting of liquid formulations of amino acids, fats, sugars, vitamins, and minerals, before competitions [77]. Antidiarrheal medications should be used with caution [66,78]. (See "Approach to the adult with acute diarrhea in resource-abundant settings", section on 'Symptomatic therapy'.)

Other causes — Travelers' diarrhea is the most common illness in persons traveling from resource-rich to resource-limited regions of the world, and should be considered in athletes that travel for competition. Infectious outbreaks resulting in diarrheal illnesses have been noted at athletic competitions [79,80]. GI infections can spread rapidly among team athletes since team members are in close proximity to each other [81]. The epidemiology, prevention and treatment of travelers’ diarrhea are discussed in detail, separately. (See "Travelers' diarrhea: Treatment and prevention" and "Travelers' diarrhea: Epidemiology, microbiology, clinical manifestations, and diagnosis".)

GASTROINTESTINAL BLEEDING

●Incidence – Occult bleeding has been reported in 8 to 28 percent of marathon runners and up to 84 percent of ultramarathon runners [82-88]. Overt GI bleeding is rare.

●Pathogenesis – Ischemic damage has been proposed as a causal mechanism of GI bleeding during and after exercise [82,85,89]. Acceleration and deceleration injury might result in mechanical trauma to the intestine, resulting in GI blood loss [84]. The use of non-steroidal anti-inflammatory medications may also contribute to GI mucosal damage.

●Clinical manifestations and diagnosis – Patients are usually asymptomatic. Endoscopically visible lesions in the stomach and colon have been observed in athletes in close temporal proximity to the exercise but are usually transient. Endoscopic findings include hemorrhagic gastropathy, erosive gastritis, gastric ulcers, and ischemic colitis [87,90-92]. In an illustrative study that evaluated 41 runners competing in a marathon, nine (21 percent) developed post-race fecal occult blood of whom seven underwent upper endoscopy [87]. Of the three patients who were evaluated within 48 hours, two had bleeding antral erosions, and one had hyperemia and erosions isolated to the splenic flexure on colonoscopy. In the four runners with delayed endoscopic procedures, no source of bleeding was found.

Anemia is rare in athletes and is usually multifactorial (eg, intravascular mechanical hemolysis, volume expansion) [93-103]. The evaluation of patients with occult and overt GI bleeding are discussed in detail separately. (See "Evaluation of occult gastrointestinal bleeding" and "Approach to acute lower gastrointestinal bleeding in adults" and "Approach to acute upper gastrointestinal bleeding in adults".)

●Management and prevention – Prophylactic acid suppression with a proton pump inhibitor may be effective in preventing occult GI bleeding due to gastric erosions [104,105]. However, the need for such prophylaxis is unclear, since most lesions associated with occult blood loss are transient and clinical sequelae are rare. The management of GI bleeding and ischemic colitis is similar to the general population and is discussed in detail separately. (See "Approach to acute upper gastrointestinal bleeding in adults" and "Approach to acute lower gastrointestinal bleeding in adults" and 'Intestinal ischemia' above.)

SUMMARY AND RECOMMENDATIONS

●Epidemiology and risk factors – The incidence of exercise-related gastrointestinal (GI) symptoms ranges from 20 to 96 percent. Many of these symptoms are related to physiologic changes resulting from exercise. The incidence is higher in women and in younger athletes. Risk factors include dehydration and analgesic use. Exercise-related GI symptoms are frequently associated with consumption of a meal two to three hours prior to exercise. (See 'Epidemiology and risk factors' above.)

●Exercise-related transient abdominal pain (ETAP) – Transient pain occurs in up to 68 percent of athletes. The pain is usually well localized to the subcostal regions and is relieved with cessation of physical activity. In patients with bothersome symptoms, we suggest the avoidance of high-calorie and high-fat meals and fluids at least three hours before exercising (Grade 2C). Patients with ETAP should be advised to consume frequent, small volumes of hypotonic fluids during exercise. A short-term low fermentable oligo-, di-, and monosaccharides and polyols diet may help reduce exercise-related symptoms. In patients with persistent symptoms, we suggest a temporary decrease in exercise intensity or duration (Grade 2C). (See 'Exercise-related transient abdominal pain' above.)

●Exercise-induced intestinal ischemia – Intestinal ischemia due to exercise is rare. Mesenteric and colonic ischemia in the setting of exercise is typically nonocclusive. Symptoms are usually mild and generally resolve without treatment. Patients may be present with abdominal pain, bloating, nausea, or vomiting. In patients with ischemic colitis, rectal bleeding or bloody diarrhea usually develops within 24 hours. (See 'Intestinal ischemia' above.)

●Upper gastrointestinal symptoms – Symptoms related to exercise include heartburn, regurgitation, chest pain, nausea, and vomiting. Patients should be advised to avoid high-calorie, fatty meal three hours prior to exercise and hypertonic fluids during exercise. During endurance or intense exercise, carbohydrate intake in the form of liquid supplementation may be better tolerated. The management of patients with persistent reflux symptoms usually requires acid suppression with a histamine 2 receptor antagonist or proton pump inhibitor. (See 'Gastroesophageal reflux' above and 'Nausea and vomiting' above and "Medical management of gastroesophageal reflux disease in adults".)

●Exercise-induced diarrhea – Symptoms include urgency to defecate and diarrhea during exercise. Fecal incontinence is rare. Diarrhea may be provoked by an incomplete bowel movement before starting exercise and pre-race anxiety. Exercise-induced diarrhea is typically self-limited and rarely results in dehydration or electrolyte disturbances. (See 'Exercise-induced diarrhea' above.)

●Gastrointestinal bleeding – Bleeding associated with exercise can result from hemorrhagic gastropathy, erosive gastritis, gastric ulcers, or ischemic colitis. Bleeding is usually occult and lesions are transient. Anemia due to occult blood loss is rare in athletes and if present is usually multifactorial in etiology. (See 'Gastrointestinal bleeding' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff thank Dr. John Kwon for his contributions as an author to prior versions of this topic review.