Summary of Findings and Reports of the WSAVA Gastrointestinal Standardization Group
World Small Animal Veterinary Association World Congress Proceedings, 2008
Robert J. Washabau, VMD, PhD, DACVIM
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota
St. Paul, MN, USA


The WSAVA Gastrointestinal Standardization Group was originally formulated to develop a world-wide standard for the histological evaluation and diagnosis of gastrointestinal tract diseases. Several histological grading schemes have been proposed previously but none are universally accepted. Without a uniform standard, it has been difficult to compare and contrast results reported in retrospective and prospective clinical trials. This is true of the spectrum of gastrointestinal disorders from malignancy to toxicity, infection, lymphatic dilation, inflammation, and villus atrophy. The absence of a uniform standard is further complicated by different nomenclatures for the same disease or disease severity in different parts of the world. With the support of the WSAVA, the Gastrointestinal Standardization Group has been developing a standardized histologic evaluation system for companion animal gastroenterologic disorders. Standardization should yield several obvious benefits including uniformity in the diagnosis of disease, staging of disease, and the subsequent development of controlled clinical trials for the treatment of canine and feline gastrointestinal disorders.


Several groups, including the Comparative Gastroenterology Society, European Society for Comparative Gastroenterology, and the American College of Veterinary Internal Medicine called for national and international efforts to standardize the histologic evaluation of the gastrointestinal tract of cats and dogs. The 2006 publication of the WSAVA Liver Standardization Group provided additional impetus and urgency to the need for standardization of the primary disorders of the gastrointestinal tract.

Specific Aims

1.  Scholars were organized from the specialties of Veterinary Pathology (ACVP, ECVP) and Internal Medicine (ACVIM, ECVIM) to review gastrointestinal tract diseases of dogs and cats. Clinicians and pathologists reviewed major and minor diseases of the gastrointestinal tract with the aim of standardizing language and nomenclature that are applied to the histologic diagnosis of gastrointestinal disease.

2.  Meetings of the International Working Group were held, and presentations were made, at annual meetings of the WSAVA, ACVIM, and ECVIM for the purposes of elevating the visibility and stature of the Working Group at relevant International Specialty Colleges.

Group Membership





Bilzer, Thomas


University of Dusseldorf


Day, Michael


University of Bristol


Guilford, Grant

New Zealand

Massey University

Internal Medicine

Hall, Ed


University of Bristol

Internal Medicine

Jergens, Al


Iowa State University

Internal Medicine

Mansell, Joanne


Texas A & M University


Minami, Takeo


Pet-Vet, Yokahoma


Washabau, Robert


University of Minnesota

Internal Medicine

Wilcock, Brian


HistoVet, Canada


Willard, Mike


Texas A & M University

Internal Medicine

Meetings and Group Reports

Meetings were held and comprehensive summaries of the Group's efforts were presented at the 2007 ECVIM Congress in Budapest, 2007 ACVIM Forum in Seattle, 2006 WSAVA Congress in Prague, 2005 WSAVA Congress in Mexico City, and 2004 ACVIM Forum in Minneapolis.

Publication--Journal of Comparative Pathology

Day MJ, Bilzer T, Mansell J, Wilcock B, Hall EJ, Jergens A, Minami T, Willard M and Washabau R. Histopathological standards for the diagnosis of gastrointestinal inflammation in endoscopic biopsy samples from the dog and cat: a report from the World Small Animal Veterinary Association Gastrointestinal Standardization Group. Journal of Comparative Pathology 2008; 138: S1-S43.

This is a forty-three (43) page monograph that summarizes the major histopathologic changes in inflammatory disease of the canine and feline gastrointestinal tract. The monograph is the first systematic characterization, in pictorial and textual template, of the inflammatory and morphologic changes of the stomach, small intestine, and colon of dogs and cats. The Group believes the monograph will serve as the sole standard of reference for clinicians, internists, and pathologists in their diagnosis of inflammatory bowel disease and other disorders.

Publication--Journal of Veterinary Internal Medicine

Willard M, Mansell J, Fosgate G, Gualtieri M, Olivero D, Lecoindre P, Twedt D, Collett M, Day M, Hall E, Jergens A, Simpson J, Else R, Washabau R.

Effect of sample quality upon the sensitivity of endoscopic biopsy for detecting gastric and duodenal lesions in dogs and cats. Journal of Veterinary Internal Medicine 2008; 26-page manuscript accepted for publication.

In this study, we showed that the quality of endoscopically-obtained tissue samples has a profound effect on the sensitivity of identifying certain lesions. Endoscopists should be trained to obtain the highest quality tissue samples possible and in the importance of tissue processing. Multiple samples should be taken to ensure that a sufficient number of adequate or at least marginal tissue samples are obtained during endoscopic procedures. The number of samples that need to be taken during an endoscopic procedure will depend upon the endoscopist's ability to routinely obtain adequate (or marginal) samples, and this may vary with the clinician. Our study demonstrated that the assumption that 'one clearly adequate biopsy specimen would be sufficient for diagnostic purposes' is incorrect. Our data instead suggest that the goal of obtaining 6 marginal or adequate feline duodenal or gastric samples will be sufficient to provide 99% confidence of finding histologic lesions. Six adequate duodenal samples should be sufficient in the dog except for crypt lesions, which necessitated 13 in this study. If marginal samples are taken, then 10-15 duodenal samples will be necessary (except for crypt lesions which necessitate over 20 samples). Seven adequate or 13 marginal canine gastric samples will be required. Future studies will be needed to refine these estimates. It will be important that pathologists relay their evaluation of the tissue sample quality in addition to the histologic description to provide the clinician with the most information in order to make an accurate interpretation of the histopathology results.

Publication--WSAVA Website

Gastrointestinal Endoscopy Guidelines were developed by the Group in January 2007, endorsed by the Comparative Gastroenterology Society in June 2007 and the European Society of Comparative Gastroenterology in September 2007, and posted to the WSAVA website.

The Endoscopy Guidelines will also be published as an Appendix in our Atlas (WSAVA Standards for Clinical and Histologic Diagnosis of Canine and Feline Gastrointestinal Diseases). The projected publication date for the Atlas is September 2009.

The Group has also developed and posted an expansive definition of inflammatory bowel disease (IBD) involving clinical, imaging, histologic, immunologic, pathophysiologic, and genetic criteria.

Publication--ACVIM Consensus Statement--Journal of Veterinary Internal Medicine

The Group was asked by the ACVIM Board of Regents to prepare an ACVIM Consensus Statement on Guidelines for histopathologic assessment of intestinal inflammation in the dog and cat for the 2008 ACVIM Forum in San Antonio. ACVIM Consensus Statements are designed to provide veterinarians with guidelines regarding the pathophysiology, diagnosis, or treatment of animal diseases. The foundation of the Consensus Statement is evidence-based medicine, but if such evidence is conflicting or lacking, the appointed panels provide interpretive recommendations on the basis of their collective expertise. Topics of statements and panel members to draft the statements are selected by the Board of Regents with input from the general membership.

The Group will present its preliminary report at a Full Plenary Session at the ACVIM Forum on June 7 in San Antonio, followed by a more formal publication of our Consensus Statement in the Journal of Veterinary Internal Medicine in the fall of 2008.

The key points of the ACVIM Consensus Statement are:

 Section 1--Definition and Scope of the Problem

 Section 2--Normal Histology of the Gastrointestinal Tract

 Section 3--Effects of Aging on the Histology of the Gastrointestinal Tract

 Section 4--Concordance of Findings Without Standardization

 Section 5--Development of Standards for Histopathologic Diagnosis

 Section 6--Concordance of Findings With Standardization

 Section 7--Guidelines for Biopsy Quality and Quantity

 Section 8--Important Species Differences--Dog and Cat

 Section 9--An All-Encompassing Definition of Inflammatory Bowel Disease

Publication--2008 ECVIM Congress

M Willard, G Moore, D Denton, M Day, J Mansell, T Bilzer, B Wilcox, M Gualtieri, D Oliveria, P Lecoindre, D Twedt, M Collett, E Hall, A Jergens, R Else, R Washabau. Correlation between pathologists assessing endoscopic gastric and intestinal biopsies using pictorial template with written descriptions. An abstract submitted for presentation at the 2008 ECVIM Congress in Ghent.

The Group has developed an archive of 253 glass slides with 2,287 tissue biopsies from 9 different institutions in 6 different countries. Slides have been reviewed by 4 pathology members of our Group--Thomas Bilzer, Michael Day, Joanne Mansell, and Brian Wilcock--using the standards outlined in our Journal of Comparative Pathology monograph. Observations have been entered into a spreadsheet by Dr. Al Jergens, and preliminary data analysis has been completed by Drs. Jergens and Willard. Our data show that additional work is necessary to accomplish consistency on select histologic lesions (neutrophils, eosinophils, duodenal fibrosis, gastric atrophy, deep gastric injury).We suspect that variation in staining and tissue processing contributed to the lack of agreement between pathologists on eosinophils and neutrophils.

Publication--Atlas--Blackwell Publishing

An atlas of the Group's work: WSAVA Standards for Clinical and Histologic Diagnosis of Canine and Feline Gastrointestinal Diseases, is projected for September 2009 publication. The Atlas will include the following components:

 Section 1--The Endoscopic Examination

 Section 2--The Histopathologic Examination

 Section 3--Inflammatory Bowel Disease

 Section 4--Gastrointestinal Neoplasia

 Section 5--Esophagus

 Section 6--Gastro-Esophageal Junction

 Section 7--Stomach

 Section 8--Small Intestine

 Section 9--Large Intestine

 Section 10--Interventional Endoscopic Procedures

Future Plans

The Group will likely present a proposal to the WSAVA for funding of a second cycle of activity. Projects of interest include:

1.  Development of a standard for jejunal and ileal pathology

2.  Standards for surgical biopsy of the GI tract

3.  Diagnosis and staging of gastrointestinal lymphoma, especially well-differentiated feline lymphoma

4.  Biopsy standards for the diagnosis of intestinal lymphangiectasia

5.  Relationship between histopathologic and clinical findings

Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker)

Robert J. Washabau, VMD, PhD, DACVIM
Department of Veterinary Clinical Sciences, College of Veterinary Medicine
University of Minnesota
St. Paul, Minnesota, USA

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