There should never be a casual attitude about impaction (“Thank goodness it’s only an impaction”). Instead, the view should be “Thank goodness we caught it, treated it and made sure we fixed it before it went any further.”
While not immediately life-threatening, intestinal impactions can and do progress into emergencies if the health of the bowel wall in the impacted region becomes compromised, if the bowel ruptures or if an uncomfortable horse rolls and twists or displaces the impacted area.
Impaction, as the name says, refers to a tightly packed mass of fecal material along the intestinal tract. It is often confused with constipation (difficulty having a bowel movement), which can be related to an impaction. Impaction may cause a complete or partial obstruction blockage of fecal material, fluid and gas. Conversely, impactions may occur as a result of a partial obstruction, e.g. caused by enteroliths or sand.
Colic pain related to impactions begins as a relatively mild discomfort and progresses slowly, usually over days. The degree of pain is related to the size of the impaction and how much gas and fluid can make their way around it. Severe pain is related to distention of the bowel with gas and fluid.
As long as gas and fluid can make their way around the mass of feces, the horse will not have violent pain. Gas and fluid can also move backward to a certain extent — back “up” toward the stomach. This prevents any one area from becoming severely and suddenly distended, but there is a limit to the capacity of the bowel. If the horse were a human or dog, he would start vomiting at that point. Since he can’t, he shows steadily increasing pain as the gut continues to fill.
Early signs are easy to miss, such as decreased appetite, slowness to eat or “pickiness.” Appetite wanes for two reasons. As gas, fluid and feces back up, the horse probably experiences a sensation similar to our nausea. Eating also triggers a reflex contraction/movement of the colon, which will be painful when it reaches the irritated site.
Water consumption is variable. The horse may drink less, may only drink or may spend a lot of time playing around in the water bucket — as if he knows he should drink but also knows he better not or he could get uncomfortable.
Increased flatulence (gas) is another common early sign. You may notice the horse raising his tail and passing gas but not feces.
Manure production may continue for a few days (the colon holds a lot of manure; he will continue to pass anything present past the impacted area). Manure may appear normal or drier than normal and may have a thick, rope-like mucus coating.
Once the colon is empty of contents past the impaction, the horse may seem to develop diarrhea, passing only a thin, watery manure or dark fluid and gas. Amounts are small and represent the gas and fluid contents that manage to make it past the impaction.
As pain increases, symptoms of decreased or picky appetite will too. The earliest sign of pain may simply be that the horse moves around less or more stiffly, stands in a fairly rigid, possibly somewhat stretched-out position and may hold his tail elevated more than normal. Ears may be pinned and the horse has an unpleasant or “internally preoccupied” look on his face.
The pain may come in waves, so that the horse seems OK at one time and at others is not. As pain increases, more classical colic symptoms of looking at or biting the flank and pawing may appear. The horse may also prefer to lie down. You certainly should have called the vet by this time, but if early symptoms were missed (e.g. horse turned out in a group) pain can progress to more obvious violent pawing and rolling. Little or no actual manure is passed at this point, what little may pass would be dark fluid and/or mucus.
By far the most common root cause of an impaction is inadequate water intake. A horse should never be found to have run out of water — better yet, never be even close to running out. If watering more frequently is not an option, hang an extra bucket.
Water must be clean. If you have a horse you know likes to go back and forth between feed tub and water bucket, wait until he finishes eating and then clean and refill the bucket. If the horse habitually dunks his hay, wet it before it is fed and by all means place hay and water at opposite ends of the stall to make it more of an inconvenience for him to do this.
Simply dumping and refilling buckets (or troughs) is not enough. They should be cleaned daily, more often if need be. A scum film, not necessarily visible, forms easily in buckets and needs to be removed by rubbing and rinsing. Disinfect with chlorine bleach (10% solution) or hot soapy water. If aftertaste is a problem, especially with plastic buckets that tend to “hold” odors and tastes, use extra rinses or clean the buckets with salt or baking soda. Both are abrasive enough to remove film but rinse out easier. Disinfect the bucket by allowing it to dry thoroughly in direct sunlight. Old buckets may develop tastes or odors that cannot be effectively removed. If a horse’s water consumption is not what it should be (see electrolytes, August 1999), try a new bucket.
Many horses prefer their water be within a certain temperature range. Like us, horses often appreciate a cool drink in hot weather over water that has been sitting around and heating up. In winter, watering with warm water often encourages intake.
A common management error is to assume the horse needs less water in winter because he is not sweating. While this is partially true, remember that grass contains 70 to 80% water. Hay contains less than 10%. If the horse was getting live grass spring through fall and must rely on only hay in the winter, his water needs increase due to the difference in water content of the feed. It is common to find that water provided for horses with access to plenty of grass will go untouched all day. Horses receiving hay to supplement the pasture may not drink until after they are hayed.
Some horses don’t drink enough water due to an electrolyte imbalance, specifically, a total body sodium depletion. Thirst is directly linked to sodium concentration. If the horse is not taking in enough sodium to meet his needs, his body dehydrates itself (by decreasing the urge to drink) to keep that sodium level normal.
The horse needs to take in at least 1 to 2 oz. of salt in addition to what he gets from his hay and grain. This means a stall-size salt block should last about six weeks in the winter. If the horse is not voluntarily taking in this much, try adding the salt directly to grain or switch to a loose salt mixture free choice (see electrolytes article).
If neither of these work, consider dosing the horse with the salt for about two weeks, to re-establish a normal sodium level in the body. You will see a noticeable increase in water consumption when you do this. Once sodium is back to normal levels, keep salt available free choice.
Adequate exercise is also important in preventing impaction. Mild exercise, such as walking, stimulates intestinal motility. Horses on prolonged stall confinement are obviously at risk, but horses with pain from a chronic lameness may also not move around as much as they should, even when kept turned out.
Health problems can also make impaction more likely. Horses with poorly maintained teeth often develop painful sores in the mouths. This makes drinking and chewing painful. Keep regular dental visits for your horse.
Aging is associated with decreased intestinal motility. Some of this may be a direct decline in how well the bowel functions, but multiple other factors, such as inadequate exercise and less frequent trips to water, also contribute. It is wise to consider any aged horse as an impaction case waiting to happen (see management sidebar at end of story).
Horses with previous intestinal surgery or areas of th e intestine that have been damaged by parasites are at higher risk for impaction. In the case of the horse with a history of colic surgery, the correct management program will depend on the details of the surgery. Some are best handled by a low-fiber, highly digestible diet and others just the reverse. This is a matter to discuss with your veterinarian.
Once a horse has suffered sufficient parasite damage to affect the functioning of the intestine, you can’t reverse it. Frankly, with the effectiveness of today’s deworming pastes, you have everything you need to prevent it from worsening or occurring at all.
Treatment of an impaction is a job for the vet, at least initially. Pain is usually controllable with Banamine. If the impaction is within reach, manual removal of some of the manure is done rectally using liberal amounts of lubricant. Again, depending on the location, some vets will use enemas of water only, water and mineral oil or water and DSS, which is a stool softener. The horse will also likely be tubed with a gallon of mineral oil, with or without water. Walking the horse or turn out in a paddock is often recommended, and a soft, high moisture diet (mashes) may be prescribed.
You will usually see signs of the mineral oil passing through before any manure shows although they may appear together. The impaction will take from a few hours to a day to be passed. If there are no results within 24 hours, another treatment with mineral oil by stomach tube may be advised.
Usually, persistence will get results with an impaction of feces. However, if an enterolith or large collection of sand is at the root of the problem the horse will not improve, in fact will probably worsen rapidly, and surgery will be needed.