Overview
The equine stomach (ventriculus, gaster) has a small capacity relative to the size of the animal, suited to the continuous intake of small amounts of forage. It lies in the intrathoracic part of the abdomen, mainly on the left, between the diaphragm and liver cranially and the loops of colon and small intestine caudally. Even when full it does not usually reach the abdominal floor and cannot be reached from outside.
Parts
- Blind sac (saccus caecus ventriculi): a fundic sac dorsal to the cardia, on the left, in contact with the diaphragm and the spleen.
- Cardia: oblique entry of the oesophagus with a powerful sphincter.
- Body (corpus): with the greater curvature, which carries the gastrosplenic ligament, and a sharply bent lesser curvature.
- Pyloric part: right of the median plane; it ends at the pylorus, which opens into the duodenal ampulla.
Mucosa
- Squamous region (pars nonglandularis): whitish stratified squamous epithelium lining the blind sac and part of the body.
- Margo plicatus: a raised, irregular edge that sharply separates the squamous from the glandular mucosa.
- Glandular region: a narrow strip of cardiac glands along the margo plicatus, the fundic region (proper gastric glands) and the pyloric region.
Clinical relevance
- Equine gastric ulcer syndrome: squamous disease, along the margo plicatus and the lesser curvature, is linked to intense exercise, high-concentrate diets and long gaps between meals; glandular disease occurs mainly in the pyloric antrum. It is diagnosed by gastroscopy and treated with omeprazole and management changes.
- Gastric distension and rupture: grain overload or a small intestinal obstruction that causes fluid reflux distends the stomach; because the horse cannot vomit, it may rupture along the greater curvature. Nasogastric intubation decompresses the stomach and lets the reflux be measured.
- Bots: Gasterophilus larvae attach to the mucosa near the margo plicatus and in the glandular region; they usually have little clinical impact.
- Gastric impaction: build-up of dry or fibrous feed, less common; it is recognised by gastroscopy after fasting.