Impaction colic occurs when a blockage within the horse’s gastrointestinal tract prevents the normal passage of its contents through the gut. It is usually caused by a build-up of solid material, usually drier than normal food or partially formed faeces. Occasionally there can be blockage caused by something else, such a foreign body, for example a plastic bag, a nylon hay net or occasionally parasitic worms. Impaction colics are among the most common colics seen by vets.
An impaction will cause discomfort or pain, leading to typical colic signs. The severity will depend on the size of the blockage and its location. Most commonly the obstruction is in the large colon, towards the end of the large bowel, but they can occur elsewhere. Obstructions are more of a problem further forward in the bowel with gastric impactions, while a blockage filling the stomach can be particularly problematic to treat.
While most cases of large colon impaction can be successfully treated medically, some will require surgery. If left untreated an impaction could potentially cause the gut to rupture. All colic cases should be considered as serious and veterinary advice sought immediately.
Impaction colic: signs to look out for
Typical signs will vary according to the severity and location of the impaction. In early cases of colon impaction, you may notice your horse is passing fewer droppings than normal and that the faecal balls are small, firm and dry. He may also be quieter than normal or appear to not want to eat.
What to do first
If you are seeing signs of colic in your horse, call your vet immediately.
While waiting for the vet to arrive, if possible, gently encourage your horse to walk around on grass or another soft surface, such as in an arena, but do not force the horse to walk if it is showing signs of distress.
The handler should be wearing gloves and a hard hat, while the horse should have a long line attached to their bridle or head collar. If the horse is determined to roll, then let him – this will not cause a twisted gut.
Diagnosis of impaction colic
Impaction colic is usually relatively easy to diagnose.
On arrival your vet will take note of the signs being displayed by the horse, check the horse’s vital signs and undertake a rectal examination to confirm the location of the impaction.
The most common site for an obstruction to occur is the pelvic flexure of the colon. This is a large U-bend at the bottom end of the bowel. The gut contents slow down as they turn this corner, which can result in a blockage.
Treatment for impaction colic in horses
Most colon impactions can be cleared without surgical intervention by the vet administering a combination of water, laxatives, electrolytes or other substances via a nasogastric or stomach tube that is passed into the horse’s oesophagus (gullet) towards the stomach via the nose.
Painkillers, such as phenylbutazone (bute), may be given intravenously to control the discomfort until the impaction is passed. The horse should receive minimal feed but can be allowed to drink if they wish, depending on the vet’s advice for the individual case. The horse will need to be monitored to observe colic signs and amount of faeces produced.
Walking the horse gently in hand as regular intervals will help to stimulate movement inside the gut. Your vet may need to re-examine the horse several times to check the impaction is softening and to administer more laxatives and painkillers as necessary.
Once the horse is comfortable and is passing droppings again, small amounts of laxative feed, such as grass and sloppy bran mashes, may be given, with normal feed then being slowly introduced a few day later.
In severe cases of colon impaction, more frequent dosing of water and lubricants by stomach tube is needed, and the horse may need an intravenous drip, which usually requires hospitalisation. In these cases, it can take days for an impaction to clear. Long-standing obstructions of the large colon have an increased tendency to recur.
Impactions of the small intestine are more likely to require surgery. These tend to be caused by the horse eating inappropriate foodstuffs, such as twigs or shavings. Your vet may suspect a small intestinal obstruction if he or she can feel loops of small intestine that have become distended with gas and fluid during a rectal examination or further assessment by ultrasound. Also the patient may show signs of more severe pain with any impaction in the further forward small intestine or stomach.
Without a vet it is impossible to know whether colic is the result of an impaction, impending diarrhoea or a twisted gut, so any colic must always be treated as an emergency. However, most impactions are treated successfully and horses usually make a full recovery.
What causes impaction colic in horses?
The following factors may lead to an impaction in an otherwise healthy animal:
- A change in management, such as stabling a horse that was living out at grass
- A drop in the amount of exercise a horse gets, for example box rest after an injury
- Dehydration, due to insufficient fresh water or the horse not wishing to drink very cold water in winter
- Bingeing, such as when a greedy pony gains access to the feed room or an unlimited supply of hay or haylage
- Animals that eat straw bedding are also at risk
- A horse which eats unsoaked sugar beet may develop impaction in the gut or in the oesophagus (choke)
- Animals grazing on sandy soil may take in sufficient quantities of sand to cause impaction of the colon
Impactions can also occur as a result of other conditions, such as dental problems, diseases that reduce gut mobility, repeated sedation of the horse and severe roundworm infestations, typically in young horses.
- For stabled horses in particular, feed little and often, and include plenty of roughage in the diet
- Soaking hay is a good way to ensure that the horse gets plenty of moisture, and hard feed should be wetted down – sugar beet can be a useful addition
- If your horse does not tend to drink very much, introducing a salt lick or adding a teaspoon of salt to his feed can help
- During the winter, hot water can be added to buckets to take the chill off and encourage horses to drink
- Try to leave horses that are prone to impaction out at grass as much as possible
- Regular exercise is a very important way to prevent impaction. If your horse cannot be turned out to graze, make sure he has some form of exercise daily, even if it is just walking in-hand
- Horses or ponies that eat straw should be kept on an alternative bedding, such as shavings, paper or rubber matting
Medical management of large colonic impactions pub. December 2015
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