Gastroscopy refers to the use of endoscopy to assess the stomach. A special three metre videoendoscope is required to evaluate the equine stomach, which is available both at the clinic and for multiple use in raceyards.

Equine Gastric Ulcer Syndrome (EGUS) can cause recurrent low-grade colic signs, weight loss, changes in attitude and behaviour, sub-optimal performance, as well as general signs of ill-thrift and a dull hair coat. Gastroscopy, which is performed after a period of fasting to allow full assessment of the stomach, allows a rapid and accurate evaluation of the horse's stomach lining and hence an rapid diagnosis of whether a horse is suffering from ulcers. Horses most at risk from developing ulcers include those in high intensity training, those undergoing any form of stress e.g. transportation to and from an event or being on box rest and young foals, particularly if they are sick or receiving any medications. In addition, horses receiving diets that are high in carbohydrates and protein i.e. significant quantities of concentrates, are at higher risk of developing ulcers. Images can be captured and stored for future comparison.

In certain cases, gastroscopy is also used to obtain tissue biopsies to evaluate for signs of intestinal inflammation or neoplasia, in horses suffering from weight loss.