Review of Endoscopic Gastrointestinal Tract Biopsy in Dogs and Cats

A review recently published in The Veterinary Journal discusses indications for endoscopic biopsy of the gastrointestinal tract, techniques and instruments for specimen collection, and recommendations to ensure the best diagnostic results in cats and dogs with gastrointestinal disease.

Operator experience, technique, sample processing, and histopathological grading systems affect the results of endoscopy. According to the authors, the following factors influence the diagnostic value of endoscopic biopsy:

• Endoscopic biopsy is not indicated in all patients with gastrointestinal disease, especially those that have not yet undergone therapeutic trials (anthelmintic, antimicrobial, and dietary, as appropriate). Endoscopic biopsy is less invasive and generally faster than surgical biopsy. It also allows the operator to assess mucosal lesions that are not visible from the serosal surface and to target biopsy sites accordingly. However, surgical biopsy enables full-thickness sampling and access to the entire intestinal tract. “Different clinical situations dictate a preference for surgical vs. endoscopic biopsy,” write the authors.
• An endoscopic examination should always include mucosal biopsy because histopathological examination can reveal lesions in tissue that appears grossly normal. The quality of biopsy specimens and results of mucosal evaluation may depend on the endoscopist’s level of experience.
• Collecting a sufficient number of high-quality biopsy samples improves diagnostic accuracy. The recommended number of specimens varies with the target organ (for example, 6 specimens from the stomach or 9 to 12 from the colon). Instrument choice depends partly on operator preference and experience; cytology brushes and various configurations of biopsy forceps are available.
• Biopsy samples from the ileum should always be included, say the authors. Ileal lesions can differ from duodenal lesions, and ileal biopsies may lead to a diagnosis that could not be made from duodenal samples alone. Blind biopsy through the ileocolic valve may be needed.
• The diagnostic quality of specimens can be improved with careful postbiopsy sample handling. Tissue samples can be placed on lens paper, biopsy sponges, or preserved cucumber slices before fixation in formalin. Specimen orientation can affect histopathology results.
• Pathologists may interpret samples differently, and not all pathologists use standardized guidelines such as the World Small Animal Veterinary Association criteria for mucosal inflammation. Correlation of histopathologic findings with clinical signs is not always straightforward.

Dr. Laurie Anne Walden received her doctorate in veterinary medicine from North Carolina State University. After an internship in small animal medicine and surgery at Auburn University, she returned to North Carolina, where she has been in small animal primary care practice for over 20 years. Dr. Walden is also a board-certified editor in the life sciences and owner of Walden Medical Writing, LLC.