Patients with disorders of the esophagus, stomach, or intestines may be candidates for endoscopy.

The term endoscopy refers to evaluation of the gastrointestinal tract for the presence of a wide variety of esophageal, stomach, and intestinal disorders. An endoscopy requires specialized equipment, and the veterinarian performing it must have training and expertise in the procedure.

In addition to its use as a diagnostic tool, endoscopy also has therapeutic applications. The procedure can be used to remove foreign objects from the esophagus and the stomach, to place feeding tubes into the stomach without the need for surgery, and to correct strictures, which are narrowed areas in the esophagus or colon resulting from scar tissue formation.

Endoscopy does require general anesthesia. Complications related to endoscopy are uncommon, and the procedure is non-invasive.

In small animals, endoscopy is performed under general anesthesia with a flexible, fiberoptic endoscope. The endoscope is attached to a light source, and a lens allows visualization of the areas being examined. It is often hooked up to a video camera so that the examination can be recorded. The endoscope has small channels through which biopsy forceps or retrieving instruments can be passed. Water and air can be sent through separate channels to keep the viewing area clean, and to allow for distension of the portions of the gastrointestinal tract as they are examined. Rigid endoscopes are also available, and can be very useful for evaluation of the esophagus and the lower parts of the intestinal tract. Prior to endoscopy, initial diagnostics usually include a thorough physical examination, bloodwork, and x-rays. Fecal examinations for parasites, stool cultures, and abdominal ultrasound are additional tests that may need to be considered prior to endoscopy.

Once the patient is anesthetized, the endoscope is passed into the mouth and then into the esophagus, stomach, and small intestine for the examination of the upper part or the gastrointestinal tract. Each area is carefully inspected for abnormalities that are apparent to the naked eye. Biopsies are taken from areas that appear abnormal, but also from areas that look normal since, in many cases, diseases are found on biopsy in tissues that look normal on endoscopy.

For colonoscopy, the endoscope is passed into the anus, then into the rectum, and up into the colon. The entire length of the colon can be examined, all the way to the point where the small intestine empties into the large intestine. In some circumstances, it is possible to pass the endoscope into the ileum, the last part of the small intestine, allowing for evaluation of that portion of the intestinal tract as well. If colonoscopy is done along with examination of the upper part of the gastrointestinal tract, this part of the procedure is done last.

The prognosis depends upon the diagnosis determined by the procedure. Serious complications related to endoscopy itself are rare. Anesthetic complications can occur, but these are also relatively uncommon.

Patients with a high likelihood of complications, and those that are extremely unstable should not undergo endoscopy unless it is felt that the procedure is necessary for therapeutic intervention. If portions of the gastrointestinal tract are especially devitalized due to injury or disease, rupture can occur once they are distended with air. Large ulcer craters can be perforated at the time of endoscopy, and this can lead to peritonitis.

Fasting from food is usually advised prior to endoscopy. A 12-hour fast is usually adequate prior to examination of the upper gastrointestinal tract, but in some animals, normal stomach emptying time can be as long as 16 hours after the patient's last meal. In addition, animals suspected of having problems with delayed stomach emptying might need to fast for 18 to 24 hours. For colonoscopy, fasting may be extended for 24 to 36 hours. Additional preparation required prior to colonoscopy can include the oral administration of specific medications or special solutions to help cleanse the colon prior to the procedure. Enemas may be used to accomplish the same goal. It may be difficult to do a thorough examination if there is an excessive amount of fecal material in the colon at the time of the procedure.

The care of the patient after endoscopy depends on the animal's condition prior to the procedure. Stable patients undergoing endoscopy for diagnostic purposes can usually be released after they recover completely from anesthesia. The animals should be monitored, especially around stairs and furniture, until it is certain that recovery is complete. Small amounts of food and water can be offered the evening after the procedure and normal amounts may be given the following day. Patients that are ill enough to require hospitalization, or those that recover slowly from anesthesia, are managed by the veterinarian in the hospital until their condition is adequate for release. There is no healing time associated with endoscopy, which is one of the advantages it has over surgery.