Making a specific diagnosis to determine the actual cause of the colic can be extremely difficult for veterinarians at times.
Because of the multitude of possible causes, it is of value to examine several excellent recent research reviews which looked closely at the classification of colics, and at the causative factors, incidence and mortality associated with these diseases.
The majority of cases of colic occur due to unknown causes, but are primarily presumed to be associated with intestinal muscle spasm or the accumulation of abnormal amounts of gas in a portion of the intestine. In general, colic results due to the distension of the bowel by ingesta, fluid, gas, or due to a functional impairment of the normal intestinal motility. In more severe cases, abdominal pain may be the result of damage to the intestinal wall by reduced blood supply (ischaemia), inflammation, death of tissue (infarction) or oedema (swelling and increased fluid).
The causes of colic can be classified by well recognised pathological categories, including obstruction, strangulation, enteritis/colitis, peritonitis, as well as by the site involved – stomach, small intestine, caecum, large colon, small colon, peritoneum, and other organs including liver, spleen and kidney
Rather than simply listing the types of colic which can occur, it is now of value to look at what we do actually know about causes, prevalence and risk factors, as well as strategies to prevent colics.
Nathaniel White, DVM, of the Marion Dupont Scott Equine Medical Center, Virginia, reviewed the risk factors in the USA in 2002, in his publication “Prevalence, demographics and Risk Factors for Colic, www.ivis.org, with the following comments and observations;
Out of 100 horses in the general population, 4-10 cases of colic are expected in one year.
About 10-15% of the colics are repeat cases, with some horses having 2-4 colic episodes yearly.
Horses that have had a previous colic are three times as likely to have a second colic compared to a horse that has never had colic.
Most colic signs were simple colic or ileus (no contractions of the gut) with no specific diagnosis entered in 80-85% of cases.
In one study, 30% of horses with colic were identified by owners but never seen by vets because the colic was short lived or resolved by the owner.
Studies of colic cases seen by vets reported a predominance of simple obstruction or spasmodic colic. Impaction colics made up about 10% of cases, and obstruction or strangulating diseases requiring surgery made up from 2-4% of cases.
Universities report that simple colic and impaction colics are the most commonly reported. When a specific gut location can be identified by veterinarians, the large colon is the most commonly affected, followed by small intestine, caecum and small colon respectively. Diseases which cause strangulation (twisted bowel) have the highest fatality rate- with the large colon torsions being more common than small intestine torsions.
Colic is responsible for more deaths in horses than any other disease except old age. In normal farm horse populations, horse mortality from all types of colic was 0.7 deaths per 100 horse-years, with a colic case fatality rate of 6.7%.
Risk Factors For Colic
In some colic cases the cause may be evident, such as in grain overload, but even in these cases, the exact mechanism which initiates the problem is often unknown. By looking at known risk factors we can begin to reduce the incidence by eliminating possible risk factors.
There are internal and external risk factors for colic:
While no breed is immune to colic, several studies suggest that Arabian horses have more colic episodes, while some other studies suggest...