Contributors: Ken Harkin, James Simpson

 Species: Canine   |   Classification: Techniques

Introduction Requirements Preparation Procedure Aftercare Outcomes Further Reading



  • Examination of the colonic and rectal mucosa.
  • Collection of colonic mucosal biopsy samples.
  • Investigation of:
    • Chronic diarrhea.
    • Hematochezia.
    • Dyschezia.
    • Tenesmus.


  • Non-invasive technique requiring no surgical intervention.
  • Well-tolerated by sick dogs which would be unsuitable for laparotomy.
  • Requires only light general anesthesia or heavy sedation - rapid recovery.
  • Good visualization of the alimentary mucosa.
  • Follow-up examination well-tolerated and useful for assessing response to treatment.


  • Will not detect pathology lying under the mucosa.
  • Not routinely possible to examine the small intestine.
  • Cannot carry out surgical correction compared with laparotomy.
  • Expensive equipment.

Technical Problems

  • Technical difficulty in procedures.

Alternative Techniques

Time Required


  • Induction of anesthesia and/or sedation → 10-30 min.


  • Depends on the experience of the endoscopist → approximately 15-30 min.

Decision Taking

Risk assessment

  • Low risk.
  • See complications.



Nursing expertise

  • Good level of competence required for assisting in procedures, monitoring anesthetic and assisting in biopsy collection and handling.
  • High competence for care and cleaning of endoscopic equipment.

Materials Required

Minimum equipment

  • Fully immersible, fiber-optic, flexible or rigid endoscope.
  • One meter insertion tube length.
  • 7-9 mm diameter or insertion tube.
  • ONLY use an end-viewing endoscope.
  • Four-way tip deflection.
  • MUST have cold light source with air pump and water wash facility.
  • Fenestrated biopsy forceps for collection of mucosal biopsy samples.
  • Cleaning brushes for biopsy channels.
  • Water leakage tester.

Ideal equipment

  • Video endoscope:
    • Excellent magnified image presented on screen.
    • Detection of lesions much easier.
    • Allows for multiple person viewing.
    • Excellent for video recording procedures and/or collecting still images.
    • Excellent as a training aid.
  • Xenon light source.
  • Prefer 1 m scope with 7-9 mm diameter.
  • Suction unit for aspiration of unwanted gastrointestinal secretions.
  • Cytology brushes, grasping forceps and balloon catheters.
  • More than one endoscope for examination of different parts of the gastrointestinal tract.
  • Endoscope cleaning trolly.
  • Ultrasonic cleaner for biopsy forceps.

Minimum consumables

  • Clean water.
  • Endoscope disinfectants.
  • Household detergent.
  • Formal saline, card and containers for preservation of biopsy samples.

Other requirements

Care and maintenance
  • Storage of endoscopes:
    • ALWAYS store endoscopes in a safe location where accidental knocks can be avoided.
    • ALWAYS store endoscopes with insertion tube hanging vertically.
    • Do NOT store endoscopes in their carrying case.
    • See supplier for further details of endoscope 'hangers'.
  • Cleaning and disinfection:
    • Follow the manufacturers recommendations at all times.
    • Use an endoscope cleaning bath wherever possible.
    • Use whatever disinfectant the manufacturer recommends.
    • Gigasept, Cidex and Dettol endoscopic disinfectants are available.
    • Follow health and safety rules regarding use of these products.


Dietary Preparation

  • Nil per os for a minimum of 12 hours.


Other Preparation

  • Oral intestinal cleansing agents the afternoon prior to examination.
  • Use Colyte, Golytely or similar preparation (Klean Prep or Picolax in UK).
  • Use ONLY warm water enemas on the morning of the examination.
    Bandage tail to reduce soiling and aid location of anus in long-haired breeds.

The endoscopist should wear protective clothing.



Step 1 - Pass endoscope

  • Lay patient in left lateral recumbancy.
  • Lubricate distal end of endsocope with KY gel.
  • Gently insert endoscope into the rectum and inflate with air.

Core Procedure

Step 1 - Endoscopic examination

  • Once mucosa is visualized slowly advance the endoscope examining the mucosa as you proceed.
  • Air may have to be continually used to maintain visualization but do NOT overinflate.
  • Try to advance endoscope to the ileocecocolic junction.
  • This will be recognized as a 'button like' structure with a small blind ended sac immediately adjacent.
  • Flexures separating the descending/transverse and transverse/ascending colon are recognized as 'bends' as the endsocope is advanced.
  • Collect biopsy samples from any focal lesion and from all levels of the colon.
  • Unlike other endoscopic procedures, the rectum is best examined when gently withdrawing the endoscope while maintaining air inflation.

Step 2 - Biopsy collection

  • Collect biopsy samples from any focal lesion and from all levels of the colon.
    Do not overinflate the bowel as this will make mucosa stretch tightly reducing ability to collect samples.
  • Try and advance biopsy forceps perpendicular to the mucosa.
  • Tent mucosa before closing biopsy forceps and retrieving sample.
  • Deeper samples can be collected by sampling repeatedly at the same site.
  • Perforation will occur if this is done too frequently.
  • Capillary bleeding from biopsy sites is normal.


Step 1 - Remove endoscope

  • Gently withdraw endoscope.
  • Support end of scope with swab as it is withdrawn to prevent damage.



General Care

  • Routine post-anesthetic observation.
  • Check mucous membrane color, heart and respiratory rates in case of hemorrhage.

Special precautions

  • Do not overinflate bowel. Apply only enough air to allow adequate visualization.

Potential complications

  • Arterial bleeding from biopsy sites.
  • Bowel perforation from applying too much force.
  • Iatrogenic damage to mucosa caused by advancing endoscope along bowel.


Further Reading


Refereed papers

Other sources of information

  • Simpson J W (1996) Gastrointestinal Endoscopy. In: Manual of Canine and Feline Gastroenterology. D Thomas, J W Simpson, E J Hall (editors), BSAVA, Cheltenham. p 20.
  • Tams T R (1990) Small Animal Endoscopy. C V Mosby, St Louis.


  • Key-Med UK Ltd, Keymed House, Stock Road, Southend-on-Sea, Essex SS2 5QH, UK.
  • Arnolds Veterinary Products, Cartmel Drive, Harlescott Shrewsbury SY1 3TB, UK.
  • Veterinary Endoscope Services, Alder House, High Road, Rayleigh, Essex SS6 7SA, UK.