ture frequently implicates two factors. These are
dehydration and reduced splanchnic blood flow.
The former factor has been associated with
generalized hypovolaemia, particularly in
endurance athletes, but intestinal ischaemia is
the factor most frequently linked with lower gas-
trointestinal bleeding. The diversion of blood
from the splanchnic bed to supply exercising
muscles is a well-recognized physiological phe-
nomenon. This is reported to deplete local vis-
ceral blood flow by up to 75% and establish the
basis of localized ischaemia reported to result
in symptoms such as abdominal cramping and
diarrhoea (Schwartz et al. 1990). Both the upper
and lower portions of the gastrointestinal tract
may be affected by diminished blood supply
with the gastric mucosa appearing to be particu-
larly susceptible to insult. Denied the protective
influence of its mucosal layer, the gastric fundus
is reported to be the most frequently reported
site of gastrointestinal bleeding (Brukner &
Kahn 1993). No small bowel sites of haemor-
rhage appear to have been reported, but bleeding
from the colon has been frequently reported in
association with exercise (Fogoros 1980). Docu-
mented cases have included ischaemic colitis
(Porter 1982; Pruett et al. 1985; Schaub et al. 1985;
Heeret al. 1986; Moses et al. 1988). It has also been
proposed that these cases of gut ischaemia repre-
sent a more accurate pathogenesis of the earlier
report of ‘caecal slap’.
Symptoms of altered gastrointestinal transit
As with the pathogenesis of other exercise-
related gastrointestinal symptoms, it is likely
that the causes of altered transit, in particular
diarrhoea, are several. These include the athlete’s
diet (including fluid intake), the use of medica-
tion, the influence of psychological stresses, the
intensity and mechanical effect of exercise, hor-
monal influences and the relative ischaemia of
the gut during exercise.
The term ‘runner’s trots’ was coined by
Fogoros in 1980. It has been widely considered
that the exercise-induced bloody diarrhoea with
antecedent abdominal cramps is the single most
debilitating symptom of gastrointestinal tract
disturbance to the athlete. There are many anec-
dotal references to this in both lay and profes-
sional publications. The full syndrome includes
lower abdominal cramping, the urge to defecate,
rectal bleeding, an increased frequency of bowel
movements with exercise, and frank diarrhoea
(Swain 1994). Clinicians must rule out abnormal-
ities such as irritable bowel syndrome, lactose
intolerance, coeliac disease, ulcerative colitis and
infective causes of diarrhoea before attributing
these symptoms simply to exercise. Such medica-
tions as laxatives, H 2 -antagonists, iron supple-
ments and antibiotics may also induce diarrhoea,
and less common causes, including pancreatic
disease, exercise-induced anaphylaxis, and
diverticular disease are also frequently associ-
ated with chronic recurrent symptoms of
diarrhoea.
Of greater importance to the symptomatic
athlete is the clinical management of this debili-
tating problem. Clearly the clinician’s first
responsibility is to eliminate any significant
pathology and by so doing reassure the athlete.
The pharmacological management of chronic
diarrhoea in the athlete may employ antidiar-
rhoeal agents such as loperamide, or antispas-
modics to reduce gastrointestinal motility and
thereby enhance absorption. The common anti-
spasmodics include agents from the anticholin-
ergic group of drugs: as these drugs also inhibit
sweating, their use must be balanced against
an increased risk of heat intolerance. Non-
pharmacological interventions include attention
to adequate hydration before and during exer-
cise, the avoidance of caffeine because of its
diuretic and cathartic effects, and a low-residue
meal taken several hours before running. Some
authorities also favour the establishment of a
predetermined daily ritual of bowel evacuation.
In summary, however, the management of
exercise-induced lower gastrointestinal tract
symptoms involves the established protocol of
accurate history taking, physical examination,
diagnosis by exclusion and the initial use of
non-pharmacological agents. The use of simple
antidiarrhoeal medication is widely accepted on