COLIC describes the behavioural
signs associated with abdominal
pain. Broadly speaking, when first
assessing a horse with colic it is
necessary to differentiate between
those that are associated with the
gastrointestinal tract and “false
colic”, i.e. those conditions that
present to us as colic but do not
involve the gastrointestinal tract
(such as laminitis, ovarian disease
and bladder stones).
For the purposes of this article
we shall be focusing on causes of
colic involving the gastrointestinal
tract.
A horse that is
colicking can do so for
many reasons and so
clinical signs can vary
greatly. Different stages of
colic can present in a
number of ways and one horse will
not always look the same way as
another suffering from the same
condition.
Generally, signs of colic in horses
can be divided into those of mild,
moderate and severe pain and can
include one or all of the following:
horses in mild pain can show pawing
at the ground, flank watching, curling
their lip or just not settling; moderate
pain can present as an animal rolling
occasionally, restlessness and lying
down for prolonged periods; severe
pain can present as intense pawing at
the ground, sweating up, violent
rolling and self-trauma is often noted
from damage sustained.
Pain in colic is generally a result
of either stretching or distension of
the intestines with gas/fluid/food;
unco-ordinated contraction or spasm
of the intestines; loss of blood
supply to a length of intestine or
stretching of the mesentery.
Types and causes
Defining the type of colic involved
enables the most appropriate
treatment and prognosis to be
established. Causes of colic
associated with the small intestine can
include pedunculated lipoma, ileal
impaction, herniation, grass sickness,
epiploic foramen entrapment and
enteritis.
Causes of colic associated with
the large intestine can include pelvic
flexure impaction, displacement, tympany, volvulus and sand
impaction.
Spasmodic colic is the most
common colic encountered
(Proudman, 1992), is often mild and
typically lasts a couple of hours. Loud
gut sounds are often heard over large
areas of the gastrointestinal tract and
will respond well to gut relaxants and
pain killers.
Although numerous factors are
linked to sparking an episode of
spasmodic colic, high parasite
burdens and sudden changes in diet
are most frequently implicated (Proudman, 1998; Tinker, 1997).
When discussing incidence of colic in the general population, the
prospective study by Proudman
(1992) reported that 72% of colic
cases were spasmodic or
undiagnosed; 7% surgical; 5.5%
flatulent; 5% pelvic flexure
impactions; 9.5% other impactions
and 1% colitis.
Risk factors and prevention
Prevention is always better than cure
and certainly some cases of colic are
preventable. Regular dental
examination allows identification of
problems affecting mastication;
Hillyer (2002) proposed that poor
dentition predisposes a horse to colic
although this has not been confirmed.
Regular monitoring and
appropriate treatment of intestinal
parasites will reduce the risk of colic
as confirmed by a number of studies;
especially those associated with small
strongyles and tapeworms (Proudman
and Holdstock, 2000; Uhlinger, 1990).
Blanket treatment of all horses
every 4-6 weeks is not an appropriate
method of parasite control. Worm
egg counts from faecal samples
provide us with information on worm
burden and species of worms
responsible.
Tapeworms are not reliably
measured from worm egg counts and
so a tapeworm antibody test (serum
ELISA) is required for evaluation.
With anthelmintic resistance an ever
increasing concern (Kaplan, 2002),
monitoring and targeting of parasites
is essential.
Changes to diet or inadequate
dietary content can predispose to
colic; changes in diet should take
place over a seven- to 10-day period;
forage should make up 60% of the
total diet and a constant supply of fresh water should be
provided. Concentrate feeds
should be kept to the
minimum level needed to
maintain condition and
performance, ideally divided
into three or more feeds a day
to decrease gastric and hindgut
acid production (Geor &
Harris, 2007).
Impactions are more
prevalent in those horses fed
coarse roughage with low
digestibility (White and
Dabareiner, 1997). Feeding
horses from round bales is
associated with a greater risk
of colic (Hudson, 2001).
Some vices predispose a horse to
colic, especially those that wind suck.
A link between wind-sucking and
spasmodic colic has been suggested
but not proven yet; Archer (2004)
suggests the aerophagia from wind-
sucking can create negative pressure
in the abdomen leading to movement
of bowel into the potential space in
the lesser omental sac; this is
associated with an increased risk of
large colon obstruction and
entrapment of the small intestine in
the epiploic foramen.
Horses that have a history of
previous colic are at a greater risk of
further colic episodes; this is highest
for horses that have undergone
abdominal surgery in the previous
three months (Proudman, 2002).
Colon impaction
Colic as a result of colon impaction
carries a high risk of repeat colic; the
exact cause is unknown but it is
speculated that reduction in the
number of neurons in the myenteric
plexus of the right dorsal colon and
pelvic flexure after colon impaction
alters bowel motility making repeat
obstructions more likely (Schusser
and White, 1997).
A number of studies have
identified a higher incidence of colic
in certain breeds; Arabs and
thoroughbreds are overrepresented
(Cohen, 1995; Traub-Dargatz, 2001).
Gender has some influence as
logically there are some conditions
that affect only stallions (inguinal
hernia) and mares (large colon
displacement around foaling).
For cases of simple colic, there
are no gender differences as these
cases are generally a result of
management issues. Proudman (1992) showed that
middle-aged horses were more at risk
than young or old horses but older
horses are more likely to have a
surgical lesion. Yearlings are more
likely to suffer from ileocaecal intussusceptions and older horses are
more likely to suffer from
pedunculated lipoma.
References
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cribbing and entrapment of the small intestine
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