Gastroscopy is where we pass a flexible tube with a camera and light on the end down the oesophagus (food pipe) and into the stomach. It enables us to investigate a range of abnormalities which can occur in a horse’s stomach.
Anatomy of the horse’s stomach: The stomach of the horse consists of a single large compartment, anatomically divided into 3 regions of approximately equal size. The oesophagus (food pipe) enters the stomach via a muscular sphincter called the cardia; which opens to allow food into the uppermost third of the stomach. This upper region is referred to as the squamous or non-glandular region and is covered in cells called stratified squamous epithelial cells. The remaining two‐thirds of the stomach is covered with glandular mucosal cells. This region can be further divided into the glandular region; which occupies the mid third of the stomach, and the pyloric antrum and pyloric sphincter (the stomach exit). A clear delineation between the squamous and glandular regions of the stomach is termed the margo plicatus and can be seen clearly in the photos below.
The normal equine stomach viewed from above. The endoscope has entered the stomach at 11 o’clock on this image, has curled around the top of the squamous region and is looking down towards the acid pool in the bottom third (glandular region).
This is the same stomach, viewed in close-up. This image shows a healthy margo plicatus- the clear demarcation between the glandular (dark) and squamous (light) regions of the stomach.
What are we looking for?
Gastroscopy allows us to visualise the oesophagus, stomach and first part of the small intestine in great detail and help identify problems such as parasites, tumours, structural abnormalities, foreign objects, emptying disorders and also as a tool to rule out common diseases as part of a wider health investigation. Probably the most common reason your vet may wish to perform a gastroscopy procedure is to rule in or out the presence of gastric ulceration.
In racing Thoroughbreds there is a high prevalence of gastric ulceration (some studies suggest as high as 93%). Other elite performance horses such as dressage horses have a reported prevalence of gastric disease of more than 50% seen during training. There are reliable studies that reveal the prevalence of gastric ulcer disease in the wider leisure and pleasure pony population to be similarly high.
Husbandry and management undoubtedly play an important role in all cases we see.
Equine Gastric Ulcer Syndrome (EGUS) is a broad term used to describe irritation or erosion of the stomach lining. EGUS spans a wide spectrum of severity, from an inflamed but intact stomach lining, through to widespread erosion and bleeding.
The clinical signs we vets see for horses with EGUS are variable- there certainly appears to be no correlation between clinical signs and the severity of ulcers seen at gastroscopy. Often supposedly ‘asymptomatic’ animals are identified on gastroscopy with gastric erosion and these horses respond positively to medication, suggesting the pain and impact of EGUS is significant.
A 4-point scoring system is used by vets to help classify the severity of equine ulcers, in which grade 2 or above are considered clinically significant.
Compare the image (right) of a grade 3/4 gastric ulcer case with that of the normal image above. There is full thickness erosion of the squamous region with irritation of the glandular region where these lesions cross the line of the margo plicatus. This horse presented for lean body condition and crib-biting behaviour. The areas of yellow are termed hyperkeratosis and evidence longer standing irritation.
Some typical signs of EGUS include:
•Emergence of stable vices, including box walking, cribbing or weaving
•Hard to maintain condition despite adequate food provisions
•Poor condition including dull coat
•Adverse behaviour making training and handling more difficult
•Colic in foals and occasionally in adults
•Foals may exhibit teeth grinding, excess salivation, excessive periods lying down as well as infrequent nursing and diarrhoea
Don’t overlook the less typical presentations:
•Impeded growth of foals – which in some instances can be fatal
•Poor condition including dull coat
•Behavioural changes including during ridden work
•Mild or recurrent bouts of colic
•Loading for transportation and challenging behaviour whilst travelling
•Optimal health, fitness and performance cannot be reached
How and why do gastric ulcers occur?
The upper region of the stomach (squamous region) has no secretory or absorptive function; the lower part (glandular region) is more complex and contains glands that secrete intensively corrosive hydrochloric acid (HCL). The glandular region has various protective mechanisms to prevent it from damage.
The squamous region does not have these same protective mechanisms and ulcers can form in this region when there is an increased exposure to acid (for example acid splashing around during exercise). The glandular region may also become affected if there are problems with its natural protective mechanisms.
Horses have evolved over millennia as trickle feeders, meaning they are designed to eat almost constantly and have free access to light grazing, rough pasture. In the wild, eating would only occasionally be interrupted to escape from predators or during brief periods of sleep.
In contrast our modern, domesticated horses are usually stabled and given two or three cereal (carbohydrate) based feeds a day, sometimes with only small amounts of forage or grazing time.
High carbohydrate, low-forage diets decrease stomach pH and increase acidity, meaning gastric ulceration is more likely.
Certain risk factors increase the susceptibility of the modern horse to ulcers:
•Intense exercise (which can cause the acid of the stomach to splash onto the squamous part of the stomach lining)
•Stress, including inability to perform natural behaviours and changes in routine
•Prolonged or repeat periods without forage
EGUS can only be definitively diagnosed by endoscopy. Many horse owners worry about putting their horse through a gastroscopy procedure to diagnose gastric ulcers. The good news is this procedure is straightforward, relatively quick and minimally invasive- which makes it the best way by far to diagnose equine gastric ulcers. The procedure involves a thin optical cable is passed into a horse’s stomach to check for ulceration. This can be done standing in the clinic and without an overnight stay. Our endoscopy equipment allows us a direct visualisation of certain otherwise inaccessible areas of the body. The video endoscopy system allows the image to be displayed on a small portable screen, thereby enabling the owner as well as the vet to observe and discuss the case at the same time.
If ulcers are present, treatment is advisable. Studies have shown that, as in humans, the most effective treatment are drugs called proton-pump-inhibitors (PPIs). These drugs reduce the secretion of acid into the stomach and allow the stomach lining to heal. Total healing time is usually between two and four weeks and horses can remain in training while being treated.
Changes in management are also necessary. Continuous access to fibre based feed is important. More time grazing is preferable, but stabled horses should have continuous access to hay and access to hard feeds with high starch content should be kept to a minimum. If more energy is required to fuel a high level of work, supplementing the fibre diet with oil is preferable to adding starchy hard feeds.
A diet low in easily fermentable carbohydrates and high in hay/grass forage is desirable to reduce the risk of gastric ulceration.