Gastric Impaction

What Is A Gastric Impaction And How Do We Diagnose Them?

Gastric impactions are caused by the accumulation of dehydrated ingesta in the stomach. The stomach has a naturally ‘balling’ action, and it is important not to confuse true gastric impactions with feedballs resulting from delayed gastric emptying. However, delayed gastric emptying can certainly predispose horses to developing gastric impactions!

How do we
diagnose them?

1: Abdominal ultrasonography: With a gastric impaction, the solid mass of undigested food in the stomach has been there for some time and causes the stomach to be markedly distended, which can easily be visualised using abdominal ultrasonography. The stomach normally sits between rib spaces 10-13, but in a horse with a gastric impaction, the stomach is usually distended back to at least rib space 16. We use ultrasonography rather than gastroscopy to monitor the progress of these gastric impactions- when the stomach is no longer distended on scan then the impaction has passed or at least started to pass. Horses with delayed gastric emptying after being fasted for a gastroscope do not have distended stomachs, and neither do horses who have eaten a normal amount of feed.

2: Rectal examination: these horses usually feel ‘empty’ on rectal, and the distended stomach pushing on the spleen means that the spleen can be readily palpated as it is usually sits further back and in a medial position than normal. These horses will continue to pass manure until the rest of their gut is empty and then they stop pooing. When they start to manure again this will be from the resolving gastric impaction and it usually has quite a different appearance, texture and smell!

3: Gastroscopy: we can of course visualise the feed mass with the gastroscope and occasionally when we scope a horse for ulcers we will see a ‘normal’ feedball due to delayed gastric emptying. With delayed gastric emptying the horse just needs to be starved for a longer period before repeating the scope and in a true gastric impaction, the food mass usually has a more ‘solid’ appearance to it and it will still be present after 24 hours of feed deprivation and often for more than 48 hours. Some gastric impactions can take 4-5 days to clear.

What are the clinical
signs of gastric
impactions?

Many horses with gastric impactions will show very similar signs to those of horses who have stomach ulcers

* Abnormal eating behaviour and/or eating less than normal at feed times

* Signs of mild colic/appearing uncomfortable after eating

* One of the most common clinical signs is inappetence

* Regular colicky episodes for no apparent reason

* Unexplained weight loss

* Poor/dull coat

* Decreased faecal output

* Lack of energy/not wanting to go forward

* Being ‘off’ or ‘just not right’

* Some of these horses will have a fever and an inflammatory blood profile

* Occasionally these horses show other signs like hyper salivation

What causes
gastric impactions?

* A change in hay: and not necessarily from good to bad as far as ‘quality’ is concerned – just the fact that there has been a change has been a common denominator in many of the cases we have seen.

* Feeding barley straw: this has been the definitive cause of 4 of the recent gastric impactions we have dealt with at the Valley.

* Poor teeth: this seems to be more of an issue in older horses

* Dehydration: as with pelvic flexure impactions, dehydration can be a contributing factor to gastric impactions, particularly in horses with delayed gastric emptying for any reason.

* Space-occupying lesions in the pylorus: these can lead to delayed gastric emptying and have been a contributing factor in some of the recent gastric impactions we have seen at our clinic.

In summary

1: Gastric impactions are not the same as feedballs due to delayed gastric emptying.

2: Abdominal ultrasonography is an incredibly useful diagnostic tool if your horse has colic.

3: If your horse is showing clinical signs suggestive of ulcers don’t just assume that is the problem – get your horse scoped.

4: Try to avoid abrupt changes in hay (gradual transitions are preferable wherever possible/practical)

5: Be mindful of the potential risks associated with feeding straw instead of hay

6: Ensure that your horses have regular dental checks to keep them chewing properly

7: Monitor your horses drinking and add salt to their feed to encourage drinking (autumn is when we see most gastric and pelvic flexure impactions)

8: Don’t repeatedly drench horses for sand unless you know they have sand and have ruled out a gastric impaction – if a horse has an undiagnosed gastric impaction doing this can lead to stomach rupture

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