Gastroscopy is the reference examination (the “gold standard”) for directly assessing the gastric structures of the horse. It is a minimally invasive, safe and well-tolerated procedure, performed under light sedation, which allows the horse to remain standing without the need for general anaesthesia.
Using a flexible endoscope at least 3 metres long, it is possible to visualise in detail the oesophagus, the squamous mucosa, the margo plicatus, the glandular mucosa, the pylorus and the first part of the duodenum.
The examination can be carried out either at the clinic, where ideal conditions of space and instrumentation are available, or at the yard, in the horse's stable or in a quiet area of the premises, provided that a suitable environment, good lighting and enough space to work safely are guaranteed.
This versatility, combined with the ability to record photographs and video of the lesions, makes gastroscopy an extremely useful clinical tool for diagnosis and for monitoring over time.
In modern equine medicine this examination is fundamental, above all in the diagnosis and follow-up of Equine Gastric Ulcer Syndrome (EGUS), a group of conditions that are very widespread in both sport horses and leisure horses.
Why the horse is particularly susceptible to gastric disease
The horse has anatomical, physiological and behavioural characteristics that make it inherently predisposed to developing gastric disorders, in particular Equine Gastric Ulcer Syndrome (EGUS).
The combination of a digestive system that evolved for continuous feeding and the modern management environment often creates conditions that are unfavourable to gastrointestinal balance.
1. Distinctive gastric anatomy and physiology
Continuous acid secretion
Unlike predators, the horse produces hydrochloric acid 24 hours a day, regardless of whether food is present. Prolonged absence of forage exposes the squamous mucosa to an excessively acidic environment.
A relatively small stomach
The equine stomach has a small capacity relative to body size: it is designed to receive small quantities of food almost constantly. Prolonged fasting or large meals disrupt its natural physiology.
Two distinct types of mucosa
• the squamous portion, more fragile and lacking protective mechanisms against acid;
• the glandular portion, more resistant but sensitive to inflammatory stress and to dysfunction of its defence mechanisms.
The margo plicatus, the transition zone, is particularly vulnerable.
2. Gastric motility and emptying are sensitive to stress and pain
Gastric motility in the horse is easily disturbed by:
• psychological stress,
• visceral pain,
• electrolyte disturbances,
• medication (for example NSAIDs).
Reduced motility leads to stagnation of acidic content and increased contact with the mucosa.
3. Modern management factors
Present-day living conditions differ greatly from the horse's natural biology:
Non-continuous feeding
• concentrate meals,
• low fibre intake,
• long intervals without forage.
Reduced opportunity to move
Constant movement promotes digestion and motility and reduces stress.
Intense or irregular training
Exercise increases abdominal pressure and pushes acid up towards the squamous portion of the stomach.
4. Psychological and social factors
The horse is an animal that is extremely sensitive to emotional stimuli and to day-to-day management.
Environmental stress
• isolation,
• frequent changes of yard,
• excessive noise,
• unpredictable routines.
Social stress
• separation from other horses,
• conflict between stablemates,
• reduction of natural behaviours (mutual grooming, positive interactions).
Temperament and emotions
Anxious or reactive horses, and those prone to hypervigilance, appear more predisposed to gastric disease, in particular EGGD, probably because of alterations in mucosal defence mechanisms and in motility.
5. Chronic pain and comorbidities
Musculoskeletal pain, respiratory disease, subclinical colic or postural problems can increase the production of catecholamines and cortisol, adversely affecting:
• mucus secretion,
• gastric blood flow,
• feeding behaviour,
• pyloric motility.
Main indications for gastroscopy in the horse
1. Diagnosis of Equine Gastric Ulcer Syndrome (EGUS)
- ESGD (Equine Squamous Gastric Disease)
- More common in sport horses.
- Often related to high gastric acidity and feeding management.
- EGGD (Equine Glandular Gastric Disease)
- More complex, associated with stress and multifactorial causes.
- Aim: this distinction is essential in order to devise a targeted and appropriate treatment.
2. Assessment of non-specific signs
Gastroscopy is indicated in horses showing:
- Loss of performance or reduced stamina
- Recurrent colic, or mild but frequent episodes
- Poor appetite or reduced interest in food
- Unexplained weight loss
- Behavioural changes (irritability, nervousness)
- Teeth grinding or excessive salivation
- Irritability when being saddled or worked
3. Monitoring treatment
- Documentation of the initial state of the lesions
- Assessment of the effectiveness of treatment: medication (omeprazole, misoprostol) and management changes
- Definition of the duration of therapy
- Confirmation of endoscopic healing at follow-up
4. Assessment of the oesophagus and of reflux
- Identification of oesophagitis
- Detection of food residues that cannot be explained by other diagnostic methods
- Support for the differential diagnosis of recurrent colic or motility disorders
Preparing the horse
Proper preparation is crucial in order to obtain clear images and to reduce the risks of the procedure.
Fasting and water management
- Fasting for 12–18 hours to empty the gastric contents.
- Withholding water for 2–4 hours beforehand, so as to avoid distension and reflux.
Restraint and environment
The horse is placed in a quiet environment, with adequate lighting and minimal stimulation. Reducing stress improves tolerance of the passage of the endoscope.
Sedation and drug protocols
Gastroscopy is performed under controlled sedation, generally using:
- alpha-2 agonists (detomidine, romifidine),
- possibly combined with butorphanol in more reactive horses.
Sedation must ensure:
- a steady head position,
- reduced swallowing movements,
- that the horse remains standing.
Gastroscopy technique
1. Passing the endoscope
The well-lubricated endoscope is passed through the ventral nasal meatus, advancing gently towards the nasopharynx, oesophagus and cardia.
2. Examination of the oesophagus
As the endoscope passes through the oesophagus the following are assessed:
- inflammation,
- strictures,
- food residues,
- motility abnormalities.
3. Assessment of the stomach
Once past the cardia, systematic observation of the different regions begins:
3.1 Squamous region
The portion most predisposed to the development of ESGD (Equine Squamous Gastric Disease).
The examiner looks for:
- erosions,
- ulceration,
- areas of keratinisation.
3.2 Margo plicatus
The dividing line between squamous and glandular mucosa, frequently the site of ulcerative lesions.
3.3 Glandular region
This comprises the fundus, body and antrum.
Lesions associated with EGGD (Equine Glandular Gastric Disease) may appear as:
- hyperaemia,
- deep ulceration,
- chronic inflammation,
- a “mosaic” pattern.
3.4 Pylorus and proximal duodenum
Examining this portion makes it possible to identify problems linked to recurrent colic or to disorders of intestinal motility.
4. Insufflation
Insufflated air distends the gastric walls and allows optimal observation. It is important to control the pressure in order to avoid discomfort.
5. Documentation
Every lesion is recorded and graded according to the international severity scales (0–4).
Photographs and video allow precise monitoring at subsequent examinations.
Grading of gastric ulcers in the horse
Endoscopic assessment of gastric lesions is carried out using internationally recognised grading systems, which allow a standardised estimate of severity and a reliable comparison at follow-up.
The main classifications are:
1. ESGD – Equine Squamous Gastric Disease (0–4 scale)
This scale, widely used in both practice and research, describes the extent of lesions of the squamous mucosa:
Grade 0:
• Normal mucosa, with no visible changes.
• Complete absence of erosions or ulceration.
Grade 1:
• Thickening or minimal areas of hyperkeratosis.
• Possible very slight loss of mucosal lustre.
• No true ulceration.
Grade 2:
• Superficial erosions or single small lesions.
• Limited, isolated ulceration of modest extent.
Grade 3:
• Multiple or extensive lesions.
• Deeper ulceration with irregular margins.
• Large areas involved, often confluent.
Grade 4:
• Severe, deep, extensive ulceration, with raised margins or obvious fibrin.
• Involvement of a large portion of the squamous mucosa.
• High risk of pain, anaemia, complications and poor performance.
2. EGGD – Equine Glandular Gastric Disease (descriptive classification)
Unlike ESGD, EGGD has no universally accepted numerical scale.
Assessment is morphological and is based on:
Appearance and type of lesion:
• Hyperaemia
• Oedema
• Erosions
• Punctate or diffuse ulceration
• Deep ulcers
• “Mosaic” pattern
• Presence of fibrin or necrotic material
Location:
• Fundus
• Glandular body
• Antrum
• Pylorus (one of the most frequently affected sites)
Depth and chronicity:
• Superficial lesions
• Deep lesions with indurated margins
• Signs of fibrosis or chronic inflammation
Extent:
• Focal
• Multifocal
• Diffuse
The final report should therefore include:
• A full description of the sites involved
• The type and depth of the lesions
• An estimate of inflammatory activity
• Any suspected involvement of pyloric/duodenal motility
This approach to classification is more accurate and clinically meaningful for EGGD, given the complex, multifactorial nature of the lesions.
In depth: ulcers of the margo plicatus and of the pyloric region
Ulcers located at the margo plicatus and in the pyloric region are two distinct clinical conditions, both in their pathogenic mechanism and in their endoscopic appearance.
Correctly identifying the site and type of lesion is fundamental for planning treatment and for assessing the prognosis.
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Ulcers of the margo plicatus
The margo plicatus is the sharp dividing line between the squamous (non-glandular) and the glandular mucosa, and is one of the sites most frequently involved in ESGD (Equine Squamous Gastric Disease).
Types of lesion
Ulcers of the margo plicatus may appear as:
• areas of early hyperkeratosis,
• superficial erosions,
• linear or punctate ulceration,
• deeper lesions with irregular margins and sometimes fibrin,
• confluent ulceration that may extend towards the squamous or glandular mucosa.
This region is particularly vulnerable because of its position at the boundary, where acidic content can pool.
Causes and pathogenic mechanisms
Ulcers of the margo plicatus are mainly associated with factors that increase exposure of the squamous mucosa to gastric acid:
• Prolonged fasting or non-continuous feeding management (low fibre intake).
• Intense exercise, which causes acid to splash up towards the cranial part of the stomach.
• Environmental or management stress (travel, competition, isolation).
• A diet rich in starch and sugar, which increases acid production.
• Poor saliva production (low forage intake), which reduces the natural buffering effect.
The result is direct damage to the squamous mucosa and to the transition zone of the margo plicatus.
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Ulcers of the pyloric region
The pyloric region falls within EGGD (Equine Glandular Gastric Disease), but it has characteristics of its own that make it particularly delicate and at times difficult to treat.
Types of lesion
Endoscopic abnormalities of the pyloric region may include:
• Hyperaemia and oedema of the mucosa,
• superficial erosions,
• punctate or “crater-like” ulcers,
• deep lesions with indurated margins,
• thickening or irregularity of the pyloric canal,
• the presence of mucofibrinous material,
• narrowing of the pyloric opening or suspected motor dysfunction.
Pyloric ulcers can sometimes cause delayed gastric emptying, recurrent colic and changes in appetite.
Causes and pathogenic mechanisms
Unlike squamous lesions, pyloric lesions do not depend primarily on acidity, but on a combination of factors affecting the integrity of the glandular mucosa:
• Dysfunction of mucosal defence mechanisms, such as reduced secretion of mucus and bicarbonate.
• Chronic stress and dysregulation of the neuroendocrine axis.
• Persistent inflammation related to repeated microdamage.
• Local hypoperfusion.
• Altered gastric motility, which may contribute to stagnation of acidic content in the distal region.
• A possible role for opportunistic bacteria or dysbiosis, currently the subject of research.
• Drug effects, for example prolonged use of NSAIDs.
Pyloric ulcers tend to respond more slowly and less predictably to treatment than ESGD.
Conclusions
Gastroscopy is today an indispensable tool in modern equine medicine. Being able to observe the gastric mucosa directly allows accurate diagnosis and tailored treatment, with a direct impact on the horse's welfare, performance and quality of life.
As well as playing a central role in managing established gastric disease, gastroscopy is increasingly becoming a routine examination in sport horses, a category at particular risk of gastrointestinal disease because of physical and mental stress, feeding management and frequent travel.
Periodic examinations make it possible to:
• detect lesions early, before obvious signs appear,
• optimise welfare and athletic performance,
• monitor the effectiveness of treatment and of management changes over time.
Our clinic uses modern endoscopic equipment and protocols geared towards maximum comfort and safety for the animal, offering an accurate, safe and individual approach for every horse.
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