Colic

The term "colic" means only "pain in the abdomen" or "pain in the belly". There are many causes for such pain, ranging from the mild and inconsequential to the life-threatening or fatal. One of the problems with equine colic is that it can be very difficult in the early stages to distinguish the mild from the potentially fatal. This is why all cases of abdominal pain should be taken seriously right from the onset.

A guided tour of the horse's gastro-intestinal tract (GIT or "guts") helps to explain why there are so many forms of colic. The horse's GIT is similar to that of most species but it has a number of specialised design features, some of which predispose it to colic. These are noted by an asterisk (*) below.

Once food has been chewed, it passes down the esophagus ("gullet") into the stomach. The horse has a fairly small stomach for its size (8-15 litres), a design well suited to an animal which grazes almost continuously in its natural state. After a period of digestion in the stomach, food passes into the small intestine. This part of the gut is approximately 22 m in length, with a diameter of 7-10 cm, and a capacity of 40-50 litres. The majority of the small intestine hangs from a curtain-like membrane called the mesentery*. The messentery is attached to one point in the middle of the abdomen, under the spine. (The small intestine looks like a very long sausage running along the bottom of a thin net curtain, with the top of the curtain all bunched together.) At the junction of the small and large intestines the equine GIT has a large blind-ended* outpouching over 1 m long with a capacity of 25-30 litres. This is the caecum (the horse's version of our appendix). Food passes from the small intestine into the caecum before passing into the large intestine. Together, the caecum and large intestine form the horse's "fermentation chamber", allowing it to gain nutritional support from the complex carbohydrates contained in grasses and other forage. Three to 4 metres long with a diameter of 20-25 cm along most of its length and a capacity of over 50 litres, the large intestine fills a significant part of the abdomen. Surprisingly, this large unwieldy structure is tethered to the body wall at only two points*: at its beginning (where it joins the small intestine and caecum) and at its end (where it joins the short, narrow* small colon which leads to the anus). With only two immobile points, the large intestine lies in the abdomen in a neatly-arranged double-U formation, one "U" stacked on top of the other. This arrangement entails the food making it round a number of 180 bends* (known as "flexures") in the intestine.

Major types of colic:

Impaction colic: This is the term used when the intestine becomes blocked by a firm mass of food. Impactions most commonly occur in the large intestine at one of the flexures. This is a fairly common type of colic which usually resolves relatively easily with appropriate treatment. However, an impaction may be just the first obvious sign in a more complicated case.
Gas colic: Sometimes gas builds up in the intestine, most commonly in the large intestine and/or caecum. The gas stretches the intestine, causing pain. Gas colics usually resolve fairly easily with appropriate treatment, although it is essential to ensure that there is no underlying reason for the problem.
Spasmodic colic: Some cases of colic are due to increased intestinal contractions, the abnormal spasms causing the intestines to contract painfully. These cases usually respond fairly well.
Displacement/volvulus/torsion ('twisted gut"): In a "displacement", a portion of the intestine has moved to an abnormal position in the abdomen. A "volvulvus" or "torsion" occurs when a piece of the intestine twists. The suspension of the small intestine from the mesentery (the "net curtain") and the unfixed nature of much of the large intestine predispose horses to intestinal displacements and torsions. Except in rare cases, these types of colic cause a total blockage of the intestine and require immediate surgery if the horse is to survive. In the early stages of a displacement/torsion colic, the signs may be similar to those of a horse with one of the more benign causes of colic. That is why it is important to take all cases of colic seriously, and to seek veterinary advice at an early stage.
Enteritis/colitis: Some cases of abdominal pain are due to inflammation of the small (enteritis) or large (colitis) intestines. These are serious medical cases and require immediate veterinary attention.
Gastric distension/rupture: When a horse gorges itself on grain or, even more seriously, a substance which expands when dampened like dried beet pulp, the contents of the stomach can swell. The horse's small stomach and its inability to vomit mean that in these circumstances the stomach may burst. Once this has happened death is inevitable. If you suspect that your horse may have gorged itself on concentrate feeds, seek veterinary advice immediately.
"Unknown": In many cases of colic it is impossible to determine the reason for the pain. Symptomatic treatment, close monitoring and attention to any adverse developments usually lead to resolution of the problem.

Signs of Colic

The signs of colic in horses range from almost imperceptible in mild cases to extremely violent in severe cases. The following list includes the most common signs:

lying down more than usual;
getting up and lying down repeatedly;
standing stretched out;
standing frequently as if to urinate;
turning the head towards the flank;
repeatedly curling the upper lip;
pawing the ground;
kicking at the abdomen;
rolling

What to do

The severity of the case will dictate what you do when you find your horse showing signs of colic. If he is behaving violently call your veterinarian immediately. Violent behaviour usually equates with great pain which usually equates with a serious case of colic. Time is of the essence here. Not all horses show the same severity of signs with the same type of colic, though, and some horses may become quite violent with a relatively "mild" case. If the signs of pain are less extreme, you can take a few minutes to observe the horse's appearance and behaviour before calling the veterinarian.

If possible, take his temperature, pulse and respiration rates. Note what his appetite has been like in the past day or so, and the consistency and frequency of defecation.

Has his water intake been normal?
Are his gums a normal colour?
Think about whether he has had access to any unusual feedstuffs in the past day or so, whether any medications have been administered, and whether there have been any changes in management.

Now call your veterinarian. It is important to take all food away from the horse until the veterinarian arrives. If he is nibbling at his bedding, find a way to prevent this. Walking the horse can be a useful way of distracting him from the pain, but he should not be walked to exhaustion. If the horse insists on rolling, there will be little you can do to prevent it. If possible, try to get the horse to an area where he will do himself the least damage when he rolls. But do not get hurt yourself. Do not administer any drugs until your veterinarian has seen the horse, unless he/she tells you to do so.

Prevention of colic

If you happen to be a horse, colic is probably an unfortunate fact of life. Annual colic incidences of approximately 10% are quite common. Listed below are some of the management factors which are thought to reduce colic incidence. Horses which fall into high-risk categories, such as stabled horses in intense training and fit horses recently injured, should be monitored particularly closely.

allow as much turnout as possible
maintain a regular feeding schedule
ensure constant access to clean water
provide at least 60% of digestible energy from forage
do not feed excessive digestible energy
do not feed moldy hay or grain
feed hay and water before grain
provide access to forage for as much of the day as possible
do not over graze pastures
do not feed or water horses before they have cooled out
maintain a consistent exercise regime
make all changes in diet, exercise level and management slowly
control intestinal parasites and assess efficiency periodically.

Author Janet Douglas earned her degree in Veterinary Medicine at the University of Cambridge, England. She continued her pursuit of excellence at the Equine Research Centre, Guelph, Ontario, where she focused on equine orthopaedics.