Oesophageal obstruction – ‘Choke’ in horses

Stuart Davies BVSc MRCVS, explains what happens when a horse chokes and, what we should do

Choke, a colloquial term used by horsey folk, can be a somewhat concerning term when considering the similarly named emergency medical condition suffered by humans. However, in horses ‘choke’ refers to obstruction of the muscular tube used to pass food from the mouth to the stomach, the oesophagus – not the airway itself. Therefore, horses can continue to breath and are not ‘choking’. Despite sometimes acutely severe clinical signs this condition often self resolves quickly with minimal intervention. It is important to seek veterinary advice if you are concerned your horse has had an episode of choke, to try to ascertain a cause and identify any complications as a result.

What happens?

Choke in horses is an incredibly common occurrence and has a multitude of causes. Most often it is associated with pelleted feed stuffs, which have been inadequately soaked. Once this fibre mixes with the readily produced oral saliva of the horse and swallowed it expands resulting in an obstruction. Other feeds such as apples and carrots, as well as longer fibre eg. hay, have also been associated with episodes especially in individuals where poor dentition prevents adequate mastication (chewing).

While common, reoccurrence of episodes does raise a cause for concern and requires further investigation². Often episodes of choke commence around a period of feeding, with an acute onset bilateral discharge of both saliva and food. This saliva would under normal circumstances pass from the mouth, where it is produced by the horse during chewing to neutralise stomach acid, down the oesophagus into the stomach.

While an obstruction is present, this passage does not occur and amounts increase up to a point where it exits via the nose, often resulting in aggressive coughing and gulping. The muscular oesophagus spasms in addition to the head and neck flexing and extending, which can give the impression there is a palpable obstruction in the neck region of the oesophagus. However, the most common places for obstruction to occur are at the top and at the entry to the thoracic inlet ² . Anecdotally, mild cases, which have occurred while owners have not been present and persist, can present as a mildly off-colour horse or ‘false colic’.

Diagnosis

Often diagnosis can be based upon clinical symptoms alone. However, a conversation with your vet when it first occurs can be beneficial. Removing any food material but leaving water is always the first recommendation to prevent any further build up. Often, horses can be appreciably stressed.

The common sites of obstruction are unreachable externally by an owner. However, a gentle massage down the neck may aid the movement of saliva and possibly penetration of the obstruction. In the unlucky situation where the obstruction appears to persist then veterinary intervention is necessary.

 

Treatment

Different treatment approaches will be taken depending on experience and the mixed scientific evidence surrounding different therapies. The mainstay of treatment involves sedation, muscle relaxants and anti-inflammatories.

Passage of a nasogastric tube via the nose into the oesophagus can confirm the location of the obstruction in inconspicuous cases. Lavage of the obstruction is then performed repeatedly. Passage of a nasogastric tube can often seem easy when watching a skilled vet. However, this should not be attempted nor likewise, lavage via the mouth using a large amount of liquid, by any lay person due to the high risk of aspiration (discussed below).

Lavage continues until the obstruction is clear and the tube can be passed into the stomach or alternatively, until no further improvement is made and a rest period or further intervention is decided upon. Care must be taken to prevent the generation of high pressure within the oesophagus causing long lasting damage, such as perforation and stricture formation. Sedative drugs are necessary to maintain low head carriage, preventing aspiration of food and lavage fluids, in addition to patient compliance⁴

Oxytocin is a commonly used reproductive drug increasing the tone of the uterus. However, it has been shown, in healthy horses, to induce a short-lasting relaxation of the smooth muscle within the oesophagus (approximately last 1/3)³. Acepromazine is a well-used sedative drug, which has been associated with muscle relaxant properties. However, studies have failed to determine significant differences in oesophageal pressure when used so it may be of more benefit due to its sedative properties⁴ If episodes of choke are recurrent or, last over a 3-hour period oesophageal endoscopy is recommended. This could just be a stubborn large amount of dry sugar beet. However, recurrent cases have been shown to have a greater association with anatomical causes compared to one off occurrences. Motility issues and diverticula of the oesophgus have been identified as causes of recurrent choke. Recurrent or chronic obstructions pose a greater risk for complication development such as:

• Dehydration Perforation of the oesophagus
• Stricture formation – ulceration of the mucosa heals as a tight band reducing lumen diameter

Therefore, obstruction is more likely to occur. It should be noted that these occur commonly in foals for an unknown reason. These can be treated with by balloon dilation⁵

Aspiration pneumonia resulting from the aspiration of food, saliva and lavage fluids into the lungs will impair lung function and can in cases require aggressive treatment. One study showed that a respiration rate (RR) of 22 breaths per minute (bpm) increased the risk of developing aspiration pneumonia 6 fold in comparison to a horse with a RR of 12 bpm.

What to do

So, advice if you suspect your horse to be suffering or to have suffered with choke, is to remove any feed and try to keep the horse calm if possible. Call the vet and massage the left side of the horse’s neck gently to try to aid clearance. Even in cases that clear spontaneously keep a close eye on the horse’s respiration rate, temperature and, for any nasal discharge over the following week.

Ensure routine dental care is up to date and for food guzzlers use a salt lick in the middle of the bucket to slow down prehension.

References

1. Fubini, S. (2019) ‘Esophagus’ in Equine Surgery. Editor(s): Jörg A. Auer, John A. Stick, Jan M. Kümmerle, Timo Prange. WB Saunders (Fifth Edition). Pages 474-496
2. Feige K, Schwarzwald C, Furst A, et al. (2000) ‘Esophageal obstruction in horses: A retrospective study of 34 cases’. Can Vet J; 41: 207– 210
3. Meyer, G.A., Rashmir-Raven, A., Helms, R.J. and Brashier, M. (2000), ‘The effect of oxytocin on contractility of the equine oesophagus: a potential treatment for oesophageal obstruction’. Equine Veterinary Journal, 32: 151-155
4. Wooldridge AA, Eades SC, Hosgood GL, et al. (2002) ‘Effects of treatment with oxytocin, xylazine butorphanol, guaifenesin, acepromazine, and detomidine on esophageal manometric pressure in conscious horses’. Am J Vet Res ;63:1738–1744
5. Chidlow, H.B., Robbins, E.G. and Slovis, N.M. (2017), ‘Balloon dilation to treat oesophageal strictures in five foals’. Equine Vet Educ, 29: 609-616