CHAPTER 35 • GASTROENTEROLOGY 209LOWER GI DISEASES
RUNNER’S DIARRHEA
- Runner’s diarrhea is a spectrum of exertional or imme-
diately postexertional lower GI symptoms. Complaints
range from abdominal cramping and fecal urgency to
diarrhea and frank incontinence. Often runner’s diar-
rhea occurs in association with increases in training
mileage or with particularly strenuous training ses-
sions and competitions. An individual may be able to
endure an episode by transiently reducing their pace.
When symptoms are more severe, it may be necessary
to suspend their workout and quickly seek relief. - While the true etiology of runner’s diarrhea remains
unknown, several physiologic mechanisms have been
proposed. One theory is that it is related to the auto-
nomic nervous system. Increased parasympathetic
output during moderate exercise may intensify peri-
stalsis leading to cramping and rapid bowel transit.
Heightened sympathetic tone during more intense
exercise, could lead to increased bowel activity by
increasing the release of hormones such as gastrin and
motilin (Cammack et al, 1982). Alternatively, strenu-
ous exercise may lead to rapid shifts in intestinal fluid
and electrolytes, causing colonic irritability (Rehrer
et al, 1989). Another hypothesis is that the 70–80%
reduction in splanchnic blood flow with vigorous
exercise may lead to an ischemic enteropathy. Poor
tissue perfusion maintained over the length of the
exercise session could cause mucosal ischemia lead-
ing to fluid shifts and diarrhea. This theory could also
explain the high prevalence of GI bleeding in
marathon runners (Bounous and Mcardle, 1990).- In addition to the basics, the history should document
any recent travel, unusual food ingestion, or exposure
to sick contacts to determine a potential infectious eti-
ology. Diarrhea not associated with training should
prompt a more intensive investigation. A focused lab
assessment includes fecal occult blood testing and a
complete blood count to look for anemia. In the pres-
ence of severe diarrhea, serum electrolytes should be
drawn. Liver enzymes and pancreatic enzymes can be
considered. If the history is suggestive of an infectious
process, the stool should be examined for leukocytes,
ova, parasites, and stool cultures.
•Treatment starts with a temporary reduction in training
intensity and duration for 1 to 2 weeks. In most cases
this alone is enough to abolish symptoms (Fogoros,
1980). During this time, cross training with low or non-
impact activities can be used to maintain the athlete’s
aerobic capacity. Any dietary or fluid replacement trig-
gers should be eliminated. If a specific trigger is not
identified, individuals with ongoing symptoms may
benefit from dietary manipulation. A diet low in fiber
can be helpful (Brouns, Saris, and Reher, 1987). While
not an adequate regimen for the control of chronic
symptoms, some individuals may benefit from a com-
plete liquid diet on the day prior to competition or
scheduled intense exercise session. Once the diarrhea is
under control, a full return to high intensity exercise can
be achieved by gradually increasing training as symp-
toms tolerate. Antidiarrhealmedication should be used
sparingly and with great caution. Anstispasmodics such
as loperamide, are generally safe; however, anticholin-
ergic medications such as diphenoxylate with atropine
(Lomotil) are to be avoided because of the increased
heat injury risk secondary to their effect on sweating.
Consult GI for unresolved symptoms despite conserva-
tive therapy or for red flag symptoms.
ABDOMINAL PAIN—”SIDE STITCH”- In the young, active population, abdominal pain with
exertion is common. The conditions previously dis-
cussed notwithstanding, the “side stitch” is the most
common cause of this in athletes. Typically seen in
runners, it presents as a somewhat pleuritic aching sen-
sation, usually in the right upper abdominal quadrant.
It is often seen in deconditioned individuals starting an
exercise program, but can also be observed in athletes
intensifying their training. Exercise in the postprandial
TABLE 35-2 Regimens for Treatment of Helicobacter
pylori Infection
REGIMEN ERADICATION RATE∗
PPI bid
Amoxicillin 1000 mg bid 96.4%
Clarithromycin 500 mg bid
PPI bid
Bismuth subsalicylate 525 mg qid 85–90%
Tetracycline 500 mg qid
Metronidazole 250 mg qid
PPI bid
Metronidazole 500 mg bid 89.8%
Clarithromycin 500 mg bid
PPI bid
Amoxicillin 1000 mg bid 79.0%
Metronidazole 500 mg bid
SOURCE: O’Connor FG: Gastrointestinal problems in runners, in
Textbook of Running Medicine,1st ed. New York, NY, McGraw-Hill.
- (With permission)
*All eradication are rates based on a 7-day regimen. Though European
data suggest 7 days are adequate, this has not been confirmed by U.S.
studies. Thus, a full 14-day treatment course is recommended.