The past few years have seen a significant amount of research into gastric diseases of equids – particularly equine gastric ulcer syndrome (EGUS) – although it is very uncommon for new diseases, diagnostics or treatments to be reported.
The majority of research has looked at the treatment of gastric ulceration (both glandular and squamous), as well as some interesting case reports and work looking at the microbiome within horses.
Throughout this article the most recent research will be presented – and due to a number of new papers reviewing gastric impactions, a more extensive discussion will look into this disease.
Diagnostics
Gastroscopy remains the gold standard for evaluating most diseases within the stomach, although ultrasound can be a helpful imaging modality.
In any disease where a primary liver or inflammatory state is considered a possibility then a full haematology and biochemistry should also be run.
Ultrasound of the stomach
Abdominal ultrasound is a commonly used imaging modality, but the stomach has a highly variable size and shape depending on whether the horse has been fed, starved, stomach tubed and so on, making interpretation complicated.
Epstein and Hall (2022) evaluated a number of fed, non-fed, post‑nasogastric fluid administration and post‑reflux horses. They found that stomach size (as measured by how many intercostal spaces; ICS it spans) ranged from 0.3ICS in unfed horses to 9.0ICS in horses that had just drunk. Most usefully, this study showed fed horses had a stomach size that was 6.4ICS ± 3.7ICS.
These numbers are based on relatively few animals (n=5), but do highlight that stomach size alone should not be used as a tool to diagnose diseases such as gastric impaction.
Conditions
Gastric ulceration
Both equine glandular gastric disease (EGGD) and equine squamous gastric disease (ESGD) are very common within the equine population. Their diagnosis and treatments are well described in the literature, with excellent review articles in Vet Times previously. Therefore, only new articles will be reviewed.
The use of NSAIDs, both in starved and fed horses, is a risk period for formation of ulcers. Starvation, such as for colic or pre‑operation, can exacerbate the risk of NSAIDs.
Therefore, Bishop et al (2022) looked at how best to prevent ulceration in these cases. By comparing the administration of sucralfate and omeprazole as monotherapies, they were able to show that omeprazole (1mg/kg orally every 24 hours) was significantly superior to sucralfate (20mg/kg orally every 8 hours).
This study was limited by the fact it did not have a control group where no treatment was administered. However, based on this study it would be advisable to consider omeprazole therapy in those patients being starved and administered NSAIDs at the same time.
A wider‑reaching study by Whitfield‑Cargile et al (2021) reviewed whether phenylbutazone would affect the barrier function of the gastrointestinal tract, as well as cause ulcers. Their study evaluated whether an increase occurred in circulating bacterial 16S rDNA (a non-specific bacterial marker), which would indicate a failure of the gastrointestinal barrier, as well as reviewing gastroscope images of horses given phenylbutazone.
The study found a threefold increase occurred in circulating 16S rDNA, indicating a reduction in the barrier function of the intestine, as well as an increase in gastric injury.
The study also evaluated the use of a nutritional therapeutic, which showed that when given in conjunction with phenylbutazone, no increase occurred in 16S rDNA, nor an increase in gastric injury.
Although this therapeutic is not available in the UK, it does indicate adjunctive therapies may reduce the risk of gastrointestinal damage.
Husbandry is known to be a cause of ESGD, although many contradictory papers exist in the literature.
A very interesting study by Luthersson et al (2022) evaluated whether moving feral Icelandic ponies from pasture to a training yard would increase, or decrease, the incidence of gastric ulceration (both EGGD and EGUS).
They found the rate of EGUS reduced from 71.6% of ponies being affected at pasture to 25.4 per cent in a training yard, and their analysis showed the provision of preserved forage three or more times a day greatly reduced the rate of EGUS.
There did not appear to be a variable that was correlated with the more modest reduction of EGGD from 47% to 40.8%.
Care should be taken in overanalysing this study when comparing to other breeds and significantly different pasture types.
A more recent area of research, both in humans and equids, is the gastrointestinal microbiome. Variations in the microbiome of animals seems to play a significant role in their health and disease states.
A correlation between changes in the microbial community structure and EGGD has been shown in a number of studies (Paul et al, 2021; Voss et al, 2022), while Voss et al (2022) showed that reductions in Sarcina were specifically seen with EGGD and could be used as a way of monitoring and treating EGGD.
Although the reason for this reduction – or the effect it will have on the stomach – is not known, it shows the complexity of this disease process.
The same group were able to show different feeds lead to different microbiomes within the glandular mucosa. Therefore, could a correlation exist between feed, the microbiome and ulceration?
The clinical signs of gastric ulcers are highly variable, with several papers commenting on them.
Busechian et al (2022) attempted to investigate if a decreased body condition score (BCS) was associated with EGUS. In their study, they did not find a correlation between a reduced BCS and ulcers, although they were not attempting to assess whether a change occurred in the BCS of those horses; only whether horses that presented to them had a lower BCS when they had ulcers.
Therefore, care should be taken when interpreting these results.
Gastroscopy is the only way to diagnose gastric ulcers currently. Multiple studies have looked at haematological biomarkers as a potential mode of diagnosis, but so far none have been viable.
More recently, a number of groups have been assessing biomarkers within saliva – and although still very much an area of research rather than commercially available, progress is being made.
Muñoz-Prieto et al (2022) looked at 23 markers, of which 17 were different in EGUS patients. On further review, only 3 showed significance in being able to discriminate between EGUS and normal horses. This could become a less invasive way of diagnosing a very common disease, although it appears the process is a number of years away.
Following diagnosis, a grading system for most diseases can be used to facilitate repeat examinations and comparison of post‑treatment disease. The European College of Equine Internal Medicine (ECEIM) has created some guidelines on descriptors to try to help with consistency, but concerns had previously been raised as to the repeatability of these descriptors.
Pratt et al (2022) reviewed 92 gastroscopes, and all four observers graded the EGGD based on the ECEIM guidelines (location, severity, distribution, pronouncement and appearance). The study found limited correlation between observers, and that this current technique for recording and grading was not appropriate.
This study was in agreement with that of Tallon and Hewetson (2021), which looked at two different scoring systems, and used 49 diplomates and 33 non-diplomates.
Therefore, further investigation and – eventually – creation of an appropriate grading system would be helpful, but while this is not available, storage of all appropriate pictures is required for correlation between rechecks.
Treatment of EGUS is well described and needs little conversation, while the treatment of EGGD remains a point of further research.
Several treatment options are available to the practitioner, including oral omeprazole, misoprostol, sucralfate and injectable omeprazole. When deciding which treatment to undertake, the clinician must base this primarily on the cascade and evidence‑based medicine.
Oral omeprazole as a monotherapy has a relatively poor success rate compared to combination therapy with sucralfate and/or misoprostol, but Gough et al (2022) reviewed the use of monotherapy oral or monotherapy long acting injectable omeprazole.
Their results showed the injectable omeprazole available in the UK was non‑inferior to oral omeprazole for the treatment of EGGD. Therefore, it could be considered for treatment of EGGD as long as the cascade is fulfilled.
Gastric impaction
Gastric impaction can be a fatal disease with the inciting cause rarely being elucidated in the horse.
Horses will often present with highly variable clinical signs, including acute or chronic colic, weight loss, lethargy, inappetence, abdominal distension or a group of non-specific signs.
In the author’s experience, horses with gastric impactions seem to frequently present with non‑specific signs and weight loss over several weeks.
The diagnosis of gastric impaction can be difficult as many horses will have delayed gastric emptying, giving the impression of an impaction on gastroscopy, while the size of the stomach on ultrasound is highly variable, as previously discussed.
Therefore, the diagnosis must be made via multiple modalities to reduce the risk of overinterpreting one. These include:
- Gastroscopy – it is essential that if a gastric impaction is suspected, starvation before gastroscopy is at least 24 hours. Feed can often appear to be rounded within the stomach and take on the appearance of faecal matter in normal to slightly delayed emptying stomachs. Therefore, by waiting for 24 hours, it is very unlikely a remaining, large, dry ball of food is normal.
- Abdominal ultrasound – the stomach should be approximately six rib spaces in diameter, but if it is larger and has displaced the spleen – allowing the stomach to touch the abdominal wall – this can be an indicator of an impaction. Care should be taken as some horses have larger stomachs and those that wind suck can have incredibly large stomachs. It is rare to see the contents of the stomach as air is often mixed in the ingesta, disrupting the ultrasound.
- Peritoneal tap – if concern exists regarding a neoplasia, a peritoneal tap can occasionally highlight neoplastic cells. If neoplasia is a differential, it is worth collecting a large volume of peritoneal fluid, centrifuging the sample and analysing the pellet, knowing that the cell count is obviously not indicative of the true cell count. In impactions, though, it is the author’s experience that they are often mildly inflammatory with a slight elevation in total protein and total nucleated cells, but no evidence of erythrocytes or lactate elevation.
- Haematology and biochemistry should be performed, as cases of hepatic insufficiency often lead to gastric impactions and the bloods are regularly inflammatory, although this is a non‑specific marker.
Often the cause of the gastric impaction is unknown, even once it has been successfully cleared with medical management. Potential causes of gastric impaction include:
- squamous cell carcinoma (Rocafort Ferrer et al, 2021) or other neoplasia
- Brunner’s gland hyperplasia within the duodenum (Scarin et al, 2021)
- persimmon impaction (unlikely in the UK)
- dental disease
- lack of water
- motility issues
The author has found it to be far more efficient to treat gastric impactions with a constant‑rate infusion (CRI) of nasogastric fluids via an indwelling nasogastric tube rather than boluses of fluids. Treatment can still take many days (even going on beyond a week), and when the course of treatment is extended partial parenteral nutrition should be considered.
Witt et al (2021) undertook a retrospective case study to assess if the use of cola in the treatment of gastric impactions had an impact on survival. They found those treated with cola were more likely to survive to discharge, with 82.8% surviving compared to 35.8%. They also found Friesians were overrepresented for gastric impactions.
We have been using cola for most cases and have found the addition beneficial, although sometimes it can induce low‑level discomfort, attributed to gas. One problem we see with a CRI of fluids via nasogastric tube is that many patients seem to colic excessively for the volume of fluid being instilled.
Treatment is often started at 500ml/hour to 1,000ml/hour, but even in large horses this can lead to colic.
Therefore, we often must provide adequate analgesia for these horses with the addition of lidocaine, although care must be taken to not mask severe pain and allow a gastric rupture to occur.
Neoplasia
Gastric squamous cell carcinoma is always a concern when presented with a horse with gastric impaction, delayed gastric emptying or potentially recurrent choke.
Rocafort Ferrer et al (2021) presented seven cases where most clinical signs were non‑specific, such as weight loss, anorexia, fever, tachycardia and tachypnoea. Diagnosis in all cases was achieved by gastroscopy, although three horses had distal oesophageal growths precluding complete gastroscopy.
Other diagnostic modalities used included ultrasound that confirmed thickening of the gastric mucosa in four horses and neoplastic cells in peritoneal fluid in two horses.
Biopsies were achieved in three horses, giving a definitive antemortem diagnosis, and these were either via ultrasound or gastroscopy.
Treatment was attempted in three horses, but was unsuccessful, with euthanasia undertaken within four weeks.
Phlegmonous gastritis
Phlegmonous gastritis (a severe bacterial invasion of the gastric wall) was a disease process reported in humans, but not horses until recently.
Engiles et al (2022) reported on two two‑year‑old fillies that presented with pyrexia, lethargy, hypoproteinaemia and had previously been diagnosed with Lawsonia intracellularis. Diagnosis was made on ultrasound with severe gastric mural inflammation and oedema, but due to the severity of the signs one horse was euthanised immediately, while the other was treated with antibiotics and supportive care, but was euthanised three weeks later. Both horses had mixed bacterial populations, including Clostridium perfringens, that were confined to the submucosa of the stomach.
This is a highly unusual case report, but highlights the need for a complete clinical evaluation of cases.
Conclusions
Gastric ulceration remains the most common disease of the stomach seen in horses, but a number of disease processes should be considered by clinicians.
Often the diseases will have non-specific signs (including ulceration); therefore, a complete clinical examination should be performed so unusual diseases are not missed.
- Some drugs in this article are used under the cascade.
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