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Don’t take colic lightly

This article has appeared previously with Equestrian Life. To see what's in our latest issue, click here.

Horse eating grass. Photo supplied.

 

The phone rings: ”Doc I think my horse has colic”. It brings to mind so many possibilities of what could be wrong and what the outcome will be. Why?

BY DR MAXINE BRAIN

COLIC IN HORSES can be anything from a simple self-limiting spasm to a critical emergency that requires urgent attention if the horse is to have any chance of surviving. So what is colic? Colic is a term used to describe any form of abdominal pain. It is usually manifested by one or more of these symptoms: restlessness, sweating, pawing, flank watching, stretching, lying down, kicking at the abdomen, rolling and throwing themselves on the ground. Most people consider colic synonymous with some form of gastrointestinal (GIT) abnormality; however, colic pain can come from any abdominal organ and can include issues associated with the liver, kidneys, bladder and uterus.  As in most cases, the pain is GIT in origin; this discussion on colic will be limited to pain originating from the gut and not include colic from non-gastrointestinal causes, but the reader should be aware that they exist.

Colic can result from a simple constipation (termed “impaction” in horses), to an excess gas build-up in the intestine, to catastrophic intestinal torsions or twists. The vast majority of colic cases seen in general practice are known as medical colic, that is, they don’t require surgical intervention to treat the horse. Conversely, specialist veterinarians and referral hospitals see many more surgical colic cases, but this is because most medical colics are dealt with successfully before there is a need for the equine patient to visit a hospital. There are instances, though, when even a medical colic will need to be referred to a specialist equine hospital for intensive care in order to achieve a successful outcome, but fortunately these, too, are in the minority of cases.

Most colic cases start off looking the same; the horse is a little unsettled or uncomfortable, so it is how quickly the horse deteriorates or how it responds to treatment that helps us decide what is wrong and how to deal with it. When faced with a colicky horse, a thorough history is vital. Questions that are important (apart from the standard questions of age, sex, and breed) include:

¥    How long the horse has been colicky and how quickly has it progressed? (Sudden onset vs “not right” for a few days; low-grade pain vs uncontrollable pain.)
¥    What has the horse been doing both in the weeks leading up to the episode and immediately before the colic? (Swimming can cause some horses to get colic very soon after they get out of the pool.)
¥    Have there been any changes to the horse’s diet? (Including close attention to types of feed the horse has been on, what it has been changed to, when it was changed and if there has been a change in the amount of feed.)
¥    Has the horse passed any faeces? (Including the amount of faeces, whether it is hard and dry or soft, and whether the horse has had diarrhoea.)
¥    What is the worming history of the horse? (Has it been wormed and if so when and what wormer was used?)
¥    Has the horse had previous bouts of colic? (When and how often has it had colic and has it been related to any particular event that you are aware of?)
¥    Has the horse been on any medications? (Things that may affect the GIT include phenylbutazone, antibiotics and ulcer medications.)
¥    How long since the horse has had its teeth done? (Particularly important in older horses where poor dentition can occur.)
¥    Has the horse had access to unsafe grazing environments? (Chemically treated pastures, excessive sandy areas, toxic plants.)
¥    Are there other horses affected? (Does the owner have a lot of horses prone to colic attacks?)

Once all these questions (and more!) have been answered, the vet often has a general idea as to what they might be the cause of the colic. They will then examine the horse, paying particular attention to heart rate, gut noises, temperature, gum colour and degree of pain. Based on these results the vet will decide whether further diagnostic tests are needed or  the horse can be treated based on the findings thus far. Whilst it is not always easy to identify the exact cause of the colic at the first visit, the vet will often gain an impression as to whether the colic is medical or surgical and treat accordingly. In some cases, however, the vet may need to see the horse on more than one occasion to ascertain whether the colic is surgical or not based on the horse’s response to treatment and the deterioration of clinical signs over time.

It is vitally important that if a horse requires surgery to correct an intestinal lesion, the decision to operate is made early as time is crucial to survival. The longer the surgery is delayed, the more risk that damaged gut may need to be removed due to the gut dying.  Removing sections of intestine increases the risk of complications following surgery, so minimising the time to surgery reduces the degree of damage and increases the success rate.

Common causes

1)    Spasmodic colic - this is a fairly common cause of colic in routine horse practice and is a result of spasms in the intestines causing increased stretching of the receptors in the gut and increased peristalsis or movement of the gut. Inciting factors are thought to be things like physical exertion, increased excitement, swimming, feed changes or poor quality forage. Although it can be painful for some horses, most horses with spasmodic colic display only mild to moderate degrees of pain and show only mild changes to clinical parameters (slight elevation of heart and respiratory rates, increase in gut noises and normal to increased passage of faeces). They generally respond well to medical therapy and rarely require more than one visit by the veterinarian.

2)    Impaction colic - these are blockages which occur along the GIT. Most often they involve ingesta impacted in the caecum or the large bowel, which gradually becomes drier and harder making passage through the gut even more difficult. These are usually slow in onset and do not cause severe clinical signs until the impaction becomes so bad that it blocks the GIT completely. Treatment can involve laxatives, oral or IV fluids (serious cases) and pain relief.

Impaction can occur in the small intestines as a result of feed impaction, strictures or foreign bodies.  Occasionally foreign objects inadvertently ingested by the horse cause a blockage which results in ingesta banking up and becoming secondarily impacted (plastic bags, lead ropes). Whilst these may be treated medically, if there’s only a partial blockage, many of these will require surgery due to their poor response to oral fluids and the increased risk of complications, which occur when the small intestine is distended for prolonged periods of time.

Impaction can also involve the stomach (gastric impaction), but this is less common than large intestinal impactions and potentially much more serious.  These can occur when horses are fed certain feeds (beet pulp, wheat, barley, straw) which dry out in the stomach and cannot be passed through into the small intestine, causing the stomach to enlarge. If left untreated, gastric impactions can lead to rupture of the stomach and death of the horse. Medical treatment in the form of gastric lavage may occasionally be successful but often surgery is required in these cases.

3)    Sand colic - horses grazing in very sandy soils or in sand yards may ingest large amounts of sand which accumulates in the gut. This can affect the horse in two different ways: one, it can cause an impaction of the gut (so could come under the category of impaction colic) or two, it can cause an irritation of the gut resulting in discomfort and diarrhoea. Usually these colics are treated with what is commonly termed “sand lube”, which is a form of psyllium hydrophilic mucilloid (also known as Metamucil for humans). It can be given as a drench or fed daily for a period of time.

4)    Tympanic colic - This results from excessive build-up of gas along the GIT. It can be the result of overfeeding highly fermentable feeds such as lush pasture, clover and grass clippings or rapid consumptions of these feeds. The gas produced cannot be expelled as quickly as it is accumulated, causing the gut to distend and affecting motility of the gut. Gas can also accumulate with conditions such as late pregnancy, where part of the GIT is temporarily blocked by the foetus preventing the gas from moving through the tract.  Treatment is centred around removal of the gas or facilitation of its passage through and can involve nasogastric intubation, exercise, analgesics and paraffin oil.

5)    Anterior enteritis, enteritis and colitis - these are not common causes of colic but they can occur and usually are a result of an infectious agent.   Anterior enteritis has been associated with Clostridium bacteria in the small intestine and can present very similarly to a small intestinal surgical lesion.  They require intensive medical therapy, including IV fluids, frequent decompression of the stomach with a nasogastric tube and endotoxic medications and/or antibiotics.  They are treated surgically by some equine specialists. Colitis involves the large intestine and often results in profuse diarrhoea affecting horses infected with salmonella spp or clostridium spp.  These horses can show colic symptoms prior to them breaking with diarrhoea, so must be considered in early colic cases

6)    Surgical colics – These include conditions referred to as intestinal catastrophes (intestinal torsions or strangulations), displacements and entrapments of areas of intestine.  Most surgical colics are emergencies as the intestines, both large and small, can rapidly become compromised when the blood supply to the gut is reduced or cut off. This happens when the gut becomes twisted, entrapped or strangulated, causing the blood vessels to be damaged.  If not corrected early enough, portions of the intestine die and need to be removed.  Sometimes the gut is displaced or in the wrong position to where it should be and surgery is required to flip it back into position.  These colics usually do reasonably well as there is little or no involvement of the blood vessels, so the gut remains healthy despite the need of surgical intervention.

7)    Miscellaneous causes - These may also include uncommon events where areas of gut have become non-functional or have died as a result of conditions such as tumours, infiltrative diseases, blood clots or damaged blood vessels. These can present as various types of colic depending on how the gut is affected.

Treatment

Despite the plethora of initiating causes resulting in colic, treatment options are often similar for all. Treatment aims are centred on relieving pain, restoring normal gut movement, correcting hydration and electrolyte abnormalities, treating endotoxaemia and removing any identifiable cause such as parasites or infections.  Surgical colic requires surgical intervention to correct the initiating cause, but the same principles of treatment also apply (pain relief, fluid therapy and treatment of endotoxaemia).

Analgesia

Administration of some form of pain relief is essential either during or shortly after the examination is completed, not only for the humane reason of relieving pain but also to minimise the risk of injury to the horse and the handlers. There are numerous drugs available to help with pain relief, but the common drugs in Australia are flunixin, dipyrone/hyoscine, ketoprofen, phenylbutazone, xylazine, detomidine, romifidine and butorphanol. Sometimes it is necessary to give some form of sedation as well to allow the horse to be examined if it is too distressed.

Xylazine, detomidine and romifidine (known as alpha2 agonists), are often given in colic cases because as well as providing fairly strong analgesia, they produce quite pronounced sedation, depending on the dosage, which allows the horse to be examined properly. The duration of these drugs is often short, so they are useful in that they provide short-term pain relief to allow the horse to be examined while not masking the clinical signs for long periods of time so the veterinarian can reassess the horse more frequently.

Flunixin, phenylbutazone, dipyrone and ketoprofen are members of the non-steroidal anti-inflammatory drug (NSAID) group of drugs. They are used to provide pain relief both in surgical and non-surgical colic and their duration of effect is typically longer than the alpha2 agonists listed above. They are useful when the veterinarian is happy that the colic does not need to be assessed in a short period of time and that a longer period of pain relief is required to allow for other forms of therapy to work, for instance, to allow time for the ingesta to move through the intestines following a paraffin oil drench.

Butorphanol is what is known as a narcotic analgesic and it provides good analgesia, particularly if used in combination with the alpha2 agonists.

Laxatives

These are designed to either soften the ingesta or lubricate the surface of the hardened ingesta to encourage passage through the intestines.  Commonly used laxatives include paraffin oil, psyllium hydrophilic mucilloid, Epsom salts (magnesium sulfate), dioctyl sodium succinate.

Fluid Therapy

Intravenous fluids (drips) are predominantly used in severe colic cases where the horse is dehydrated and has significant electrolyte and acid/base imbalances.  Fluids are given to stabilise the cardiovascular system, particularly in horses with surgical colic prior to anaesthesia. The type of fluid and the amount given may vary between veterinarians, but the aim is the same; to replace the loss of fluid from the circulatory system so the heart can maintain blood flow to vital organs and prevent the horse going into shock.

There are some medical colics which are non-responsive to routine therapies that also require IV fluids for treatment. Here they are given to replace fluids lost when the colic has been going for an extended period of time resulting in electrolyte and fluid losses. In cases of stubborn impactions, IV fluids are given in large amounts to over-hydrate the horse, creating a large influx of water into the large intestine. Fluid is drawn into the impacted ingesta resulting in softening of the mass to allow it to move through the gut.

Fluids can also be given orally (via a stomach tube) in cases of colic where fluids are required but there is no compromise of the cardiovascular system.  These cases tend to be only mild to moderate and where there is adequate blood flow to the gut to absorb the fluid and electrolytes.

Spasmolytics

These reduce pain by decreasing muscle contractions and slowing down the movement of the gut. The main one used in horse practice is called Hyoscine and it is commercially available as part of a combination of drugs (hyoscine and dipyrone).

Anti-endotoxic therapies

Endotoxins are toxins associated with the outer surface of particular bacteria, which gain access into the bloodstream when the intestine wall is damaged during severe bouts of colic, in particular when the intestines are twisted or strangulated. Endotoxaemia (endotoxins in the blood stream) can be potentially fatal and cause a cascade of events in the horse, resulting in the horse having poor distribution of blood to its vital organs, death of tissues and toxic shock. It is important in severe colics, or any colic in which the gut wall has been potentially damaged, that the horse be protected from endotoxins. Flunixin is the main drug used in Australia to help suppress the negative effects of endotoxaemia and it is given as small doses two to three  times a day (compared to the larger doses used for pain relief).  Overseas products such as endotoxic-specific IgG, containing antibodies, or immunisation and hyper-immune plasma, directed against the endotoxic causing bacteria, are used.  How well these products work has not been established.

There are many more medications available that can be used in some form to assist with colic and with post-operative colic management, but they are beyond the scope of this article.

In summary, colic is never just colic. Until assessed, colic has the potential to be anything and prompt veterinary assessment is essential, especially if pain is severe, unrelenting or recurring. Careful choice of appropriate medication and monitoring of response to treatment are paramount to maximising the best outcome for the horse, even if the outcome is not always favourable. It is important that pain be managed until the horse recovers or a decision is made to go for surgery or euthanise if prognosis is hopeless. Thankfully, the vast majority of colicky horses do recover and go on to lead a productive life, even if they give us grey hair at the time!
 

 

 

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