Contributors: Ken Harkin, James Simpson

 Species: Canine   |   Classification: Techniques

Introduction Requirements Preparation Procedure Aftercare Outcomes Further Reading



Most difficult of all endoscopic procedures.
  • Examination of the small intestinal mucosa.
  • Collection of small intestinal biopsy samples.
  • Collection of duodenal aspirate for small intestinal bacterial overgrowth (SIBO) Antibiotic-responsive diarrhea (ARD) detection.
  • Investigation of:


  • Non-invasive technique requiring no surgical intervention.
  • Well-tolerated by sick dogs which would be unsuitable for laparotomy.
  • Requires only light general anesthesia → 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.
  • Does not detect motility disorders.
  • Not routinely possible to examine the entire 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 30-40 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 endoscope.
  • 1-1.5 meter insertion tube length.
  • ONLY use an end-viewing endoscope.
  • Outside diameter of insertion tube 6-7 mm to aid intubation of duodenum although most animals can accommodate a 7-9.0 mm tube.
  • 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.
  • Insertion tube diameter 6 mm or 7 mm or larger if possible.
  • 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.
  • Formaline, card and containers for preservation of biopsy samples.

Ideal consumables

  • Endoscopic (Portex) catheters for collection of small intestinal aspirates.
  • Collection bottles for duodenal aspirates.

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.



  • Suitable premedication.

Dietary Preparation

  • Nil per os for a minimum of 12 hours.


  • Light general anesthesia.

Other Preparation

  • Oral intestinal cleansing agents the afternoon prior to examination may be used.
  • Use Klean Prep, Golytely, Picolax or similar preparation.



Step 1 - Patient preparation

  • Following induction of anesthesia - it is essential to intubate patient.
  • Tie endotracheal tube to mandible NOT maxilla, to aid passage of endoscope.
  • Lay patient in left lateral recumbancy.
  • Place mouth gag to protect endoscope.
  • Pass endoscope.
  • Insert endoscope along hard palate and into proximal esophagus Endoscopy introduction of esophagoscope into esophagus.
  • Slowly pass endoscope along the esophagus.

Step 2 - Enter stomach

  • Once cardia is reached gently apply force on endoscope to enter stomach.
  • 'Red out' will occur during intubation of stomach (vision is lost).
  • Once you feel the endoscope pass the cardia, STOP, gently inflate stomach with air.
  • Do NOT examine the stomach but inflate with only the minimum amount of air to permit passage of the endoscope to the pylorus.
    Excessive air will close the pylorus, making duodenal intubation impossible.

Step 3 - Identify pylorus

  • Pass endoscope along antrum to visualize the pylorus.
  • Bile may be observed entering the stomach as may antral peristaltic contraction.

Core Procedure

Step 1 - Entering the duodenum

Intubation of the duodenum is the hardest endoscopic procedure to carry out.
  • Gently move the endoscope tip towards the pylorus, 'red out' will occur again.
  • Maintain gentle pressure, do NOT force the endoscope, until resistance is reduced indicating passage into the duodenum.
    Often the 'red out' will become a 'yellow out' indicating the presence of bile and entry into the duodenum.
  • At this point inflate with air until mucosa is visualized.
  • Advance endoscope along the duodenum examining the mucosa as you proceed Enteroscopy: duodenal mucosal lipogranulomas.
  • Note the mucosa has a velvet appearance which is different to the stomach.
  • Collect biopsy samples from different levels of the duodenum.
  • With 1.5 m insertion tubes the jejunum may be examined, but NOT the ileum.

Step 2 - Biopsy collection

  • 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 into stomach.
  • Examine the stomach at this time Gastroscopy if required.
  • Withdraw endoscope from patient.
    Support end of scope 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.
  • Check there is no evidence of gastric dilation.

Special precautions

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

Potential complications

  • Arterial bleeding from biopsy sites (rare).
  • Bowel perforation from applying too much force especially during intubation of duodenum.
  • Iatrogenic damage to mucosa caused by advancing endoscope along bowel.


Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Willard M D, Lovering S L, Cohen N D et al (2001) Quality of tissue specimens obtained endoscopically from the duodenum of dogs and cats. JAVMA 219 (4), 474-479 PubMed.

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 (eds), 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.