The term colic actually means abdominal pain. However, over time, it has become a broad term for a variety of conditions that cause a horse to exhibit clinical signs of pain. It is not a disease; more accurately it is defined as a clinical presentation characterized by a variety of symptoms.
It should be remembered that, as a species, horses have a very low pain threshold, and no two horses have the same level of pain sensation.
The "severity" of pain behavior, therefore, does not always predict the "severity" of the underlying cause of pain.
Signs of colic are often very different among different horses. An observant and knowledgeable owner or barn manager usually suspects the onset of colic before overt symptoms are apparent, especially if the owner/handler is familiar with the normal behavior/attitude of that particular horse. Typical examples are the horse that is lying down too much, is slightly lethargic, or is not eating as vigorously as usual. These signs in a horse without a fever could easily mean colic.
"Mild" Abdominal Pain
- Off feed/inappetent
- Pawing at the ground
- Facial expression of apprehension
- Looking toward flanks
- Excessive lying down
- Repeatedly lying down/standing up
- Frequent attempts to urinate but not much urine is produced
- Tail twitching
- Abnormal stance (as if to urinate)-looks like straining to urinate
- Kicks at belly occasionally
"Moderate" Abdominal Pain
- Horse may be depressed or excited
- The horse may make repeated attempts to go down and even roll; some horses may thrash dangerously
- Not interested in feed usually
- Increased respiratory effort
- Spontaneous vocalization
"Severe" Abdominal Pain
- Uncontrollable and dangerous rolling and thrashing on the ground
- Throwing itself to the ground
- Profuse sweating
- Rapid and pronounced respiratory effort
- May inflict self-trauma or self mutilation
- Facial expression of marked apprehension
- Grinding the teeth (odontoprisis/bruxism)
- Ignores attempts at restraint
Some other signs of colic that are not behavioral include
- Decreased defecation (may be initially increased)
- Cessation of defecation
- Patchy sweating
- Trembling/muscle fasciculations
For most horses affected with colic, the treatment should be preceded by a thorough examination. The veterinarian's examination should include a rectal palpation of the horse's abdomen. The thorough examination is necessary because it is important to determine whether an intestinal twist has occurred or not. If twisting is suspected, the horse must receive emergency treatment (pain relief, fluid support, and gastric decompression) and then be quickly transported to a veterinary surgical hospital.
Fortunately, most cases of colic can be readily treated by the veterinarian at the farm. Certainly, the most important treatment for colic (the behavioral effect of pain) is the administration of a pain-relieving drug, usually via intravenous injection. Veterinarians use several different drugs for this purpose.
In addition to the pain-relieving treatment, a laxative is normally given as well. The laxative is given after the veterinarian has checked the stomach for fluid distention. If the stomach is distended with fluid, it may be necessary to refer the horse to a hospital facility for treatment. In most colic cases, the stomach does not contain excess fluid and a laxative, such as mineral oil, is given.
Following control of pain and administration of a laxative, the horse may be held off feed for several hours. If the horse is allowed to consume food too soon after treatment, before the obstruction has been relieved, the additional food will simply contribute to the obstruction. It is sometimes necessary to repeat the treatments with both pain-relieving injections and laxatives before the cause of colic will resolve.
The veterinarian knows when the horse may resume feeding based on the resumption of defecation, the resolution of signs of pain, changes in the abdomen (based on palpation), and the heart rate. It is important to recognize that several hours may be needed for the obstruction to be passed. The obstruction cannot be judged to have passed before the effects of the pain-relieving medications have been allowed to wear off.
If it is not possible to control the pain associated with colic, the veterinarian may consider that referral for surgery is needed. In that event, following administration of fluids to support the circulation, the affected horse should be quickly transported to a local veterinary surgical facility.
It must be emphasized that a follow-up examination of the colicky horse is a critical component of the medical treatment. The veterinarian should re-examine the patient within a few hours of instituting treatment to ensure that the obstruction is not worsening and that twisting of the intestine is not occurring. The veterinarian will not leave the patient's side until the pain has been controlled or until the horse has been transported to a veterinary hospital facility.
Colic usually occurs when a section of the intestinal tract is obstructed in such a manner that food cannot be moved along by normal intestinal movements (peristalsis). As a result of this obstruction, gas and fluid accumulate in front of the obstruction leading to distention of that part of the intestine, which then leads to leads to pain. Inserting a balloon into the intestine and inflating it produces colic; this method has been used to test different pain relieving drugs.
A majority of cases of colic are associated with changes in the diet. For example, if a horse eats a lot of dry hay and fails to drink sufficient water, signs of colic occur as a result of simple constipation ("impaction"). There are many different causes of colic – most are associated with dietary factors.
The design of the equine intestinal tract is such that it is surprising that colic is not observed more frequently than it is. Although colic occurs rarely in wild horses, the constraints imposed by the necessities of human management (confinement and feeding) have made colic one of the most common medical problems with which domesticated horses are faced. The equine intestinal tract is very complex (compared with that of human beings and dogs). This complexity arose through evolution in conjunction with the fact that the horse, in its natural environment, roams the grasslands and depends solely on a diet of grass.
Like other herbivores, horses do not produce the enzymes necessary for the digestion of grass (hay). In order to obtain nutrients from grass, the horse's intestinal system serves to accommodate a large population of microorganisms that are capable of digesting grass, making those nutrients available to their host (the horse). The relationship between the horse and its intestinal microorganisms ("flora") is referred to as symbiosis. The large intestine of the horse functions in a similar manner to the bovine rumen, a series of fermentation chambers.
Through evolution, the symbiotic relationship between the horse and its flora depends on a uniform diet. Diet changes lead to changes in the flora and changes in the flora may adversely affect the horse's intestinal system. If the normal flora is presented with a changing variety of substrates (food) there will be changes in the make-up of the microbial population that may or may not not be significant. The microbial population is enormously adaptable and is able to adjust to many types of diet and changes in diet. However, if a diet change is sudden and/or involves a major contrast between dietary compositions, it is likely that the normal flora will be adversely affected and may result in a variety of problems (alteration in motility patterns or increased gas accumulation). The most common clinical manifestation of floral imbalance is colic.
It is therefore always recommended that any anticipated diet changes are made gradually so that the normal flora can adapt and not become overwhelmed. If the colonic flora is adversely changed beyond its ability to compensate, a number of adverse effects may arise, including: increased gas production, synthesis of toxins, and perturbation of normal intestinal motility (peristalsis).
Other factors that have been identified as increasing the risk for colic include parasite damage to the intestine, insufficient exercise, insufficient water consumption, ingestion of sand or soil (geosediment), and the effects of fear or apprehension. A substantial number of horses develop colic following thunder storms. It is believed that this association may represent an effect of fear or worry. Although much less common, numerous conditions of the intestine itself, including cancer and infections, may also lead to colic.
What is the Difference Between "True" Colic and "False" Colic?
The behavioral manifestations of colic are further classified based on the underlying cause. "Colic" presentations may be subdivided into true colics and false colic. True colic represents the situation in which the abnormal behavior is directly attributed to obstruction of the intestinal tract. False colic refers to the situation in which the behavioral abnormalities are associated with a non-intestinal problem. Some "diseases" that produce colic symptoms but are not associated with the intestinal tract include:
- Normal foaling
- Dystocia (difficult foaling)
- Uterine torsion
- Broad ligament hematoma (middle uterine artery rupture)
- Retention of placental membranes
- Aortic/iliac thrombosis
- Exertional rhabdomyolysis ("tying-up")
- Polysaccharide storage myopathy (PSSM)
- Vertebral osteopathy/fracture
- Pheochromocytoma – tumor of the adrenal gland (peri-renal hemorrhage)
- Encephalomyelitis (e.g., rabies)
- Esophageal obstruction ("choke")
- Acute laminitis
- Hypocalcemia in the mare
- Pus-distension of the scrotum following castration
- Hepatitis (liver pain and encephalopathy)
- Early anthrax
- Hyperkalemic periodic paralysis
- Heavy metal toxicity
- Purpura hemorrhagica
- Rupture of the prepubic tendon
- Extensive abdominal neoplasia
These conditions should be considered when a colic case is examined: they may give rise to clinical signs (behavior) which are properly described as colic or may which may also be causing some actual abdominal pain. The term "true colic" is reserved for those obstructive afflictions of the alimentary tract which cause manifestations of abdominal pain.
Whenever a simple colic (such as an impaction) is left untreated, there exists a risk that the intestine may become twisted within the abdomen. Twisting of the intestine represents an emergency situation for which surgical treatment is often needed.
A typical situation that commonly leads to twisting of the intestine involves the development of a simple colic during the evening time after the horse has been fed and checked for the last time. If colic subsequently develops during the night and is not recognized, the horse's attempts to roll may lead to the intestine turning on itself within the abdomen. Risk of twisting is increased by the presence of both extra gas and a heavy impaction. The combination of gas and an impaction act together to destabilize the intestine such that, when the horse rolls (response to pain) the whole intestine may turn on itself.
The presence of a twist adds to the obstruction. In many cases, the presence of a twist also leads to blockage of the intestinal blood supply and causes the affected part of the intestine to die. Twisting of the intestine is therefore very serious and, for successful treatment, requires early recognition and hospitalized care (including surgery).
Referral to a Hospital Facility
Emergency treatment of severe colic represents one of the most common reasons that horses are referred to veterinary hospital facilities. Referral may be made for various reasons, such as the need for surgery, the need for intensive care (IV fluids, etc), the need for continual observation (insufficient personnel available locally), a second opinion (primary veterinarian uncertain as to whether there is a need for surgery), and the request of the owner (some owners prefer that colic should be managed in the hospitalized environment).
Proper communication with the receiving clinician at the hospital (ideally by both telephone and in written notes sent with the client) should be made by the local (primary) veterinarian. The horse owner should be provided with directions to the hospital. If fluid accumulation in the stomach is a problem, it might be appropriate to transport the patient with an in-dwelling nasogastric tube (to prevent rupture of the stomach).
The owner of the patient should be advised by the local veterinarian regarding the likely prognosis (if known) and costs of hospitalized treatment. Some horses that arrive at the hospital for emergency surgery after a 5-hour journey are euthanatized because the cost of surgery is high and the prognosis (for some conditions) is unfavorable.
It is preferable that this type of discussion is carried out before transport, since many owners want to take their horse home for burial. This gets much more complicated once a horse has been transported to a hospital.
It might be possible to provide IV fluids during the journey in some instances; certainly further injections of pain-relieving drugs may be needed during a long journey. The colicky horse should not be fed during the trip to the hospital. Any drugs given to the patient should be done after discussion with the clinician to whom the horse is being referred.
Various diseases lead to an increased risk for mild colic. The veterinarian may address various preventive strategies or special diagnostic tests to individual horses that have been experiencing recurrent bouts of colic. If the patient has been examined and treated by different veterinarians, the precise colic history may not be apparent to the attending veterinarian. Therefore, good records of the horse's prior medical history should be maintained and made available to the veterinarian whenever possible. The medical and surgical treatment of some horses may be covered by insurance policies. In those cases, the insurance company should be notified of the horse's status as soon as possible. The insurance company may require information regarding the horse's current problem, treatment, and prognosis.
When The Owner is Absent
Sometimes, the veterinarian is called to examine and treat a horse affected with "colic" (or anything else for that matter) by someone who is NOT THE OWNER! When faced with a colic emergency, someone must take responsibility for permission to treat the horse and for meeting the veterinarian's fee.
Some horse owners leave their horses under someone else's care (for example, to go on a business or vacation trip) but fail or forget to make arrangements for the horse in the event of a medical or surgical emergency. It is recommended that whoever is in charge of the horse should have already obtained clear instructions from the owner as to how to proceed in the event of a medical or surgical emergency. In the case of "colic," specific information should include:
- Which local veterinarian should be called?
- The insurance company contact person?
- Who will be accepting responsibility for treatment administered by the veterinarian until the owner returns?
- If the colic is severe and the horse will need surgery, who will be giving permission for surgery?
- Who will be accepting responsibility for the costs of surgery in lieu of the owner?
- If the colic is severe and the prognosis (even with surgery) for survival is unfavorable or guarded, who will be responsible for providing permission for euthanasia?
How is Colic Prevented?
- Provide potable water at all times
- Critical and frequent observation of the horse
- Provide excellent quality roughage at all times
- Do not feed an excessive quantity of grain
- Prevent sudden diet changes (any necessary diet change should be gradual)
- Routine deworming, vaccination, and dental prophylaxis
- Afford regular exercise; do not stall-confine for long periods
- Prevent obesity
- Provide bran mash daily
- Occasionally, administer Metamucil™ (once every 2 weeks)
- DO NOT ADMINISTER DRUGS (especially phenylbutazone and flunixin meglumine) without appropriate justification and supervision by your veterinarian. Use of many of these drugs is known to increase the risk for colic.
Remember that individual horses that develop colic appear to be predisposed to colic for reasons that are incompletely understood. Therefore: Special attention should be paid to the individual that has developed colic at any time, and particular attention should be addressed to known preventive mesaures – see above.
Most cases of colic are simple and respond favorably to straightforward treatment. Less than 4 percent of all colic cases require surgical intervention. Most cases of colic carry a very favorable prognosis.
It should be noted that usually it is not possible to define the cause of colic in individual horses. Most horses with colic respond to nonspecific treatment and a diagnosis may not be possible.