Colic
Colic is the word that describes abdominal pain in horses and can be due to many factors because of the complex nature of the horse’s digestive system. Unlike humans, horses digest part of their food by fermentation in the huge large intestine. This is because they are herbivores and must digest large amounts of plant matter.
Food material enters the stomach from the oesophagus through a one-way valve that prevents food moving back into the oesophagus, hence the reason horses are unable to vomit. From the stomach material passes through another valve and into the small intestine. Here the food material is broken down into they key elements, fat, protein and carbohydrate and is absorbed into the blood. The food material then passes into the large intestine (caecum and large colon) where cellulose is broken down by the bacteria present. The large intestine has to fold within the abdomen due to it’s size. One of these folds, the pelvic flexure, is a common site for impactions to form. From the large intestine waste material is passed to the rectum and excreted.
Waves of muscle contractions, peristalsis, allow the flow of food material through the digestive system.
A horse that is showing signs of colic should be seen as an emergency and veterinary advice sought immediately.
Clinical signs
Horses with colic can show a variety of signs they may kick at their belly, circle, look at their flanks, roll, lie down sweat up and be off their food.
While waiting for the vet to arrive horses should have any food taken away and just left with water. If the facilities are available the horse should brought into a stable with a deep bed and banked sides.
It can be useful to walk the horses around, however, this should be done on a soft surface e.g.a ménage, as the horse may roll and injure itself further. A horse showing signs of colic
Diagnosis
The clinical signs are usually enough to diagnose that a horse has colic, however, a thorough colic examination by the attending vet can provide vital information about the severity and potential causes of the colic.
The key parts of a vet’s assessment of a horse with colic are listed below.
- Degree of Pain: An assessment of the severity of the colic can be useful, however, different horses will behave differently to similar degrees of pain.
- Pulse rate: The normal resting heart rate for a horse is between 32 and 48 beats per minute, stressed animals or those that have been rolling will have a higher heart rate. If some intestine has become damaged toxins can enter the blood stream causing the heart rate to increase significantly.
- Mucus membrane colour: Horses will normally have pale pink mucous membranes, in some colic patients this can change due to problems with blood flow caused by toxin release.
- Gut sounds: A horse’s gut sounds can be heard easily using a stethoscope. In some cases, spasmodic colic or enteritis, these sounds can be increased or in others, obstructions, be reduced or absent.
- Passing a stomach tube: A tube can be passed down the nasal passage, through the oesophagus and into the stomach. In horses with an obstruction fluid can build up in the stomach, as they cannot vomit. When the stomach tube is passed this fluid can be released, as well as preventing the stomach from rupturing this is a very good indicator that an obstruction is present.
- Rectal exam: Some abnormalities can be felt by the vet by palpating the abdominal contents via the rectum.
- Blood sample: A blood sample can be used to measure blood concentration and protein levels. This can assess the degree of dehydration and, therefore, determine whether iv fluids are required.
- Peritoneal tap: A needle can be placed into the abdominal cavity from the underside of the horse and a sample of the fluid retrieved and then analysed. Normal peritoneal fluid should be pale yellow in colour in some cases the fluid can be cloudy, red-tinged or even black. The nature of this fluid can give vital clues as to what is occurring within the abdomen.
- Ultrasound examination: Some abnormalities can be seen by scanning the abdomen, such as distended loops of small intestine.
The attending vet must build up a picture using some or all of the above techniques to assess the severity and likely causes. Most horses don’t show any major abnormalities and are treated with pain killers and/or sedation and the owner left to monitor them. Others are deemed far more severe, i.e. high heart rate, severe pain that responds poorly to pain killers, no gut sounds, abnormal on rectal exam, etc, and require further evaluation and often emergency surgery. It is at this point that many horses must be referred to a hospital with the necessary facilities.
The key thing to understand with colic is that in most cases a diagnosis as to the cause of the pain is never reached unless surgery is performed or an obvious impaction or displacement felt rectally. The vet is, therefore, assessing which causes are most likely after a careful examination, and treating it accordingly.
Approximately 80% of the colic’s I see appear to have no obvious cause and no diagnosis is reached, yet the animal has no major irregularities on clinical exam, apart from abdominal pain, and settles very well after pain killers, sedation or anti-spasmodic drugs.
Risk Factors
The risk factors for colic are recent feed changes, lack of access to water and grass, and worms.