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The University of Tennessee

The College of Veterinary Medicine

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A diffuse, ulcerated mass in the
colon of a dog

Colonoscopy is used to examine the large intestines (ileocecal valve, cecum, colon and rectum). Colonoscopy is often performed after radiographs (X-rays) and abdominal ultrasound to further evaluate patients with weight loss or diarrhea; it may also be used in concert with upper gastrointestinal endoscopy for more generalized signs of intestinal disease. Endoscopy can be used to diagnose inflammation, inflammatory bowel disease, ulcers, tumors, and fungal infections.

Uses of Colonoscopy

In addition to allowing visual examination of gastrointestinal tract, colonoscopy can be used to:

  1. Obtain tissue samples for cytologic and histologic evaluation. Samples are evaluated for inflammation, infection, fibrosis and cancer. This generally takes three to five days.
  2. Identify ‘occult’ gastrointestinal bleeding, e.g. bleeding into the intestinal tract that is not apparent to the owners or veterinarian. Such bleeding is a common cause of iron deficiency anemia in animals.


The large intestines must be cleared of fecal matter prior to colonoscopy because feces in the large intestines can obstruct the view of the gastrointestinal tract. The patient is generally hospitalized for one to two days prior to colonoscopy to allow thorough patient preparation. During this time, the patient is fasted for 24-36 hours but has free access to water. In addition to receiving warm water enemas, the patient receives a cathartic solution orally or via tube to aid in thorough preparation. After being anesthetized, the patient is placed on its left side and anesthetic monitoring equipment is attached. The patient’s heart rate and rhythm, respiratory rate, blood pressure, carbon dioxide level and oxygen saturation level are closely monitored while under anesthesia to prevent and minimize anesthesia-associated complications.

The tip of endoscope is lubricated and gently advanced through the anus into the colon. The colon is inflated with air to expand the rectum to allow advancement of the endoscope and better visualization. As the endoscope is advanced forward, the inner surface of the colon is closely examined for any abnormalities including inflammation, ulcers, and masses. Photos and videos may be collected of normal and abnormal structures and motility for documentation and further study. Gastrointestinal secretions may be removed using suction and air instilled to improve visualization of the intestinal tract. Ten to 20 biopsy samples are generally collected from the large intestine, regardless of appearance, for histopathology. This is because tissues may be diseased even if they appear normal visually.

Colonoscopy generally takes between 20 minutes and one hour depending on gross findings and number of biopsies taken. After completion of the procedure, the endoscope is slowly retracted and then the patient is recovered from anesthesia. Most patients can go home on the day of the procedure.

Risks and Limitations

Ileoscopy/colonoscopy is generally considered a safe procedure. In addition to risks or limitations of endoscopy in general, the most common finding is that some blood may be seen in the feces the day after the procedure.

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