Equine gastric ulcers are all too common, affecting up to 93% of horses. Ulcers are painful lesions that form in the lining of the gastrointestinal tract that can result in impaired nutrient absorption, discomfort, digestive complications, and poor performance in your horse.

Traditionally, veterinarians and horse owners treated and managed all gastric ulcers the same way. However, their etiology and physiology differs depending on the region of the stomach in which they appear. [1][5]

  • Equine Squamous Gastric Ulcer Syndrome (ESGUS) refers to ulcers affecting the upper squamous region of the stomach.
  • Equine Glandular Gastric Ulcer Syndrome (EGGUS) refers to ulcers affecting the lower glandular region of the stomach.

What’s the difference between squamous ulcers and glandular ulcers in horses?

Research shows that there are different risk factors and causes for squamous ulcers compared to glandular ulcers. There are also different treatment and management strategies recommended for EGGUS vs. ESGUS.

Understanding the differences between these two ulcer syndromes can help you identify, prevent, and manage gastric ulcers in your horse.

Overview of Gastric Ulcers

Equine gastric ulcers are sores or lesions in the lining of the stomach. They are one of the most commonly diagnosed health conditions in horses.

Horses are usually diagnosed with the umbrella term Equine Gastric Ulcer Syndrome (EGUS). This diagnosis can include ulcers of the squamous region and ulcers of the glandular area.

Ulcers that appear in the upper squamous region are more common than those that develop in the lower glandular region, largely due to the different natural defence systems these two regions have against ulcers.

Below, we will review further differences in risk factors, causation, diagnosis, treatment, and prevention of squamous versus glandular ulcers. [1]

Stomach Ulcers Location in Horses

The equine stomach is small but complex. It can be broken into two sections: the squamous and glandular regions. Ulcers develop in these two regions for different reasons.


Equine Squamous Gastric Ulcer Syndrome (ESGUS)

Up to 80% of all equine ulcers are found in the squamous region of the stomach, which is the upper one-third of the stomach. [2] The causes and risk factors for ESGUS are well understood.

The stomach is a harsh environment. Stomach acid (HCl) has a very low pH, making it corrosive and potentially damaging to the cells that line the inside of the stomach. This mucosal layer on the inside of the stomach is made up of epithelial cells.

HCl is continuously secreted from acid-producing cells in the glandular region of the stomach. Therefore, the epithelial cells of the glandular region are well adapted to constant contact with stomach acid and have two distinct defense mechanisms to protect themselves from degradation and damage:

  • The production of mucous, which coats the glandular epithelium.
  • The production of bicarbonate, which buffers stomach acid coming into direct contact with the stomach wall

Conversely, the epithelial cells of the squamous region of the stomach lack these defense mechanisms. This is because these cells are not routinely exposed to stomach acid for long durations. This is why ESGUS is significantly more prevalent than EGGUS. [3]

The squamous epithelium can be over-exposed to gastric acids when the stomach is empty for extended periods of time or when acid splashes up onto the squamous region, particularly during exercise.

Consumption of feed actually helps to prevent some of the damage caused by gastric acids in the squamous lining. Food, saliva, and water all work to buffer some of these acids. Feeding your horse many small meals throughout the day can help to reduce ulcer risk.

The squamous region is more susceptible to ulcers because it does not produce mucous or bicarbonate. Gastric acid can splash into this region and cause ulcers, particularly when the stomach is empty or when exercising.


Equine Glandular Gastric Ulcer Syndrome (EGGUS)

Compared to squamous ulcers, much less is known about EGGUS and the pathophysiology of this disease.

The glandular region comprises the bottom two-thirds of the stomach. [2] This region is where acid secretion takes place.

The major gastric acid secreted is hydrochloric acid (HCl). Pepsin and gastrin are also secreted in this region. These acids activate digestive enzymes to begin the breakdown of food.

As discussed previously, the glandular region produces bicarbonate and mucous. These compounds buffer gastric juices and line the stomach wall of the glandular region protecting it from acid damage.

Therefore, acid damage is not usually the cause of EGGUS. Rather, it appears that interference with these defense mechanisms and disruption of mucosal integrity are the causes of ulcers in this region. [3]

The glandular region naturally produces mucous and bicarbonate to protect against ulcers. Less is understood about why EGGUS occurs.