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AIMS OF LIVER HISTOLOGY STANDARDIZATION
The intention is to obtain worldwide standardization for histological evaluation of liver tissues for liver diseases of dogs and cats: i.e unified nomenclature, well-defined histological diagnostic criteria, and precise definition of chronicity stages and grades of diseases. Also, requirements for tissue staining techniques and size of tissue specimens will be recommended for the different diseases. The Group plans to make descriptions and typical slides of relevant liver diseases available as a reference for all veterinarians. Of course liver diagnostics is not only a matter of histopathology; therefore the relationship to clinical and laboratory findings will be indicated when necessary.

THE LIVER STUDY GROUP
The Group is made up of internationally recognized scientists in hepato-gastroenterology. The main effort will come from liver-specialized pathologists supported by expert clinicians from the USA, Europe, Australia, and South Africa. In addition we have invited one of the top human liver pathologists, as an independent back up and to help in deciding about difficult topics. There is still one vacant position for a veterinary pathologist, which will be filled shortly. Members are:

Dr. S. Bunch (USA), clinical hepatologist
Dr. J. Charles (Australia), liver pathologist
Dr. J. Cullen (USA), liver pathologist
Dr. V.J. Desmet (Europe, Belgium), human liver pathologist
Dr. T. van den Ingh (Europe, Netherlands), liver pathologist
Dr. J. van der Lugt (South Africa), liver pathologist
Dr. D. Twedt (USA), clinical hepatologist
Dr. R. Washabau (USA), gastroenterologist/hepatologist/ACVIM
Dr. J. Rothuizen (Europe, Netherlands), clinical hepatologist, coordinator of the Group.

Two meetings per year are planned over a two-year period, one during the American ACVIM forum (May each year) and one during the European ECVIM congress in September.

FIRST MEETING
The first meeting of the specialists was held in Dublin, Ireland during the ECVIM / ESVIM Congress of Internal Medicine in September 2001. Professor Boyd Jones, the organizer of the congress, had reserved a room with a multi-channel microscope, which allowed all members of the study group to judge and discuss the liver sections together. Stimulated by the pleasant environment and supported by Boyd and his staff, a lively discussion started. It was good to see that the members got along very well; although some of them did not know each other at all before, there was soon an atmosphere of friendship and cooperation. The personal chemistry could not have been better, which is an important factor in accomplishing such a challenging project.

As reported previously, the Group has divided the liver diseases to be studied into four groups:
(1) vascular liver disorders
(2) biliary tract disorders
(3) parenchymal disorders including Ito cells and Kupffer cells
(4) cancer. The first group of diseases to be studied in Dublin was the vascular liver disorders.

The vascular disorders can be subdivided as follows:
Pre-hepatic (reduced portal flow):

Congenital portosystemic shunt

"Microvascular dysplasia"

Portal vein hypoplasia

Arterioportal fistula (with acquired shunting)

Portal vein obstruction (intra- or extrahepatic hypoplasia, thrombosis, tumor,
schistosomiasis)
Post-hepatic (reduced hepatic vein flow):

Right-sided heart failure (heart, heart-base, pericardium)

Caudal vena cava obstruction (thrombus, kink, tumour)

Diffuse intrahepatic vein condition (eg, hepatic veins ["Budd-Chiari" like syndrome], terminal hepatic venules [veno-occlusive disease]).

Many months before the meeting, the Group members exchanged representative samples of tissue from all these diseases. All veterinary pathologists had selected three cases they considered to be representative of each of the above diseases, for which they had paraffin-embedded liver tissue available. If appropriate, they also selected representative cases of acute, subacute, and chronic stages, or mild, moderate, and severe stages. To enable each pathologist to make specific stains of
liver slides, four slides had to be made from each selected tissue. Each pathologist then had an identical set of slides of all diseases (ten or more cases per disease), so that it was possible to evaluate them in the months before the meeting in Dublin, and to start to discuss them over the telephone and e-mail prior to the meeting. This ended up in the production of hundreds of slides by all pathologists.

During a long day of hard work in Dublin, the members of the Liver Study Group evaluated all slides. Although there was a lot of discussion about the cases, it was not hard to reach consensus. From all the slides, typical ones were selected which were considered to represent the characteristic features of the diseases. It was agreed that Ted van den Ingh would make a collection of these typical slides, and compose a CD-rom containing pictures and descriptions. After completion of the liver standardization effort, this CD-rom will be available for all pathologists as a reference. Since the Dublin meeting, Jenny Charles, John Cullen, and Ted van den Ingh have made a summary of the discussion and have organized the selection of cases and
slides. They are preparing a presentation of the typical slides of the vascular liver diseases, which will be presented during the coming ACVIM forum in Dallas, June 2002 by John Cullen and Susan Bunch.

The preparation for the next round has already started for a new group of liver diseases. These diseases will be prepared in the coming half year and discussed in Dallas. This enterprise appears to a year-round activity! But the Group's work is on schedule, and with the great enthusiasm of the members in mind, we can expect the final results in 2003. Meanwhile, the results will be submitted for publication in a well-known scientific journal, so that they will be available as soon as possible for the entire community of liver pathologists and clinicians.

INVITATION TO ALL INTERESTED VETERINARIANS

This effort can only be performed by a small group of experts. This does not mean that the opinions of any interested veterinarians would not be important. Therefore, if you would like to comment on the procedure or the list of diseases, please feel free to submit your comments.You can approach the coordinator of the project: Dr. Jan Rothuizen, Department of Clinical Sciences of Companion Animals, University Utrecht, Yalelaan 8, 3508 TD Utrecht, The Netherlands, or e-mail at J.Rothuizen@vet.uu.nl

"The WSAVA gratefully acknowledges the enthusiastic support of Hills Pet Nutrition, Inc. in sponsoring the efforts of the Liver Standardization Group."