Colic

Description

Colic in horses is defined as abdominal discomfort or pain; it refers to a condition which can vary in cause, severity, outcome and treatment methods. The role of the veterinary surgeon is to determine the cause, make a diagnosis and initiate the appropriate treatment.

To understand the aetiology of colic we need to understand the underlying anatomy and physiology of the digestive system.

Here are some key concepts;

Horses are monogastric with a relatively small stomach capacity of 8-10 litres. The stomach is located on the left side of the abdomen beneath the rib cage.

At the distal junction of the oesophagus there is a one-way non–return valve permitting gas and ingesta to move into the stomach but not out. Conditions that impede the normal aboral movement of gas and ingesta through the digestive tract may result in discomfort, pain, distention, obstruction and potential rupture.

There can be anatomic abnormalities, such as inguinal hernias, or normal anatomical structures, such as abdominal spaces, which can cause displacement of intestines, or physiological processes, such as abnormal peristaltic motility patterns, which can cause obstructions.

Two main arteries feed the vasculature of the entire gastro intestinal system and obstructions may impede the flow of blood to organs.

Clinical Signs

There are numerous potential clinical signs for colic. Common symptoms can include;

signs of depression
lack of appetite
the horse may look and nip at its belly
perspiration
increased respiration
laying down more frequently
stretching out as if to urinate
sitting
pawing the ground
rolling or thrashing
appearing rounder than usual
unable to pass manure
abnormal gastric noises

It is important not to administer any medications to your horse without first consulting with your veterinarian, as they could mask clinical signs which are useful for diagnosis.

Causes / Risk Factors

There are many diseases which can manifest as colic. The general types of disorders outlined in the Merck Veterinary Manual which cause colic include;

distention of the intestinal lumen caused by gas, fluid or ingesta (flatulent colic)
simple obstruction of the intestinal lumen (impaction)
severe obstruction of the intestinal lumen or blood supply to the intestine (strangulating obstruction)
interruption of the blood supply to the intestine alone (nonstrangulating infarction)
inflammation of the intestine (enteritis)
inflammation of the lining of the abdominal cavity (peritonitis)
erosion of the intestinal lining (ulceration)
and “unexplained colic”

Diagnosis

Diagnosis may include;

physical assessment of the cardiopulmonary and GI systems
rectal examination and palpation
abdomen and thorax auscultation
abdominal percussion
response to nasogastric intubation

Treatment

Your veterinarian will adapt their treatment to the diagnosis of the current episode, however treatments may include;

pain relief
fluid therapy
parasite control
endotoxemia treatment
intestinal lubrication or laxatives
evacuation of intestinal contents
medical treatment
surgery, in cases with mechanical obstructions of the intestine
if necessary, surgery can be used for diagnosis as well as treatment
ultrasonography

Continuous treatment may be required for 3-5 days before clinical signs begin to subside.

Prognosis

A large retrospective study in the USA documented an overall survival rate of 60% for horses with colic and a survival rate of 50% for those horses undergoing abdominal surgery, including those euthanised during surgery for inoperative conditions. Survival rates for horses with strangulating obstruction and inflammatory diseases were only 24% and 42%, respectively. In contrast, horses with an undefined cause for the colic episode had a survival rate of 94% (Merck Vet Manual).

Management and Prevention

Colic prevention includes;

constant access to clean water
regular parasite control
free grazing
at least 1% of horse's bodyweight in roughage daily
more frequent, smaller feeds
make feed changes gradually
in sandy areas feed 400g/500kg/day psyllium powder for 7 days, repeated 2–3 times each year