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: 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. Descriptions and typical slides of all relevant liver diseases of dogs and cats should be made available as a reference for all veterinarians. Of course liver diagnostics is not only a matter of histopathology. Therefore the relation with 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, and Australia. 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 fulfilled 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. T. VanWinkle (USA), 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.

In 2001 the group had one meeting during the ESVIM congress in Dublin about the vascular liver disorders. In 2002 there were two meetings. All three were a great success. Of the entire list of canine and feline liver diseases, biliary diseases and vascular diseases of the liver most have been discussed by now. Decisions about their histopathological definition, when necessary in the context of the clinical information have been taken for a large series of diseases. The diseases of the liver were grouped into vascular diseases, diseases of the biliary system (intra- and/or extrahepatic), cystic diseases, tumors of the liver and biliary system, and parenchymal hepatic diseases.

The agreement about standards for vascular diseases had been finalized in Dublin (September 2001) and Dallas (June 2002). This consensus for histological interpretation and nomenclature was presented for the Special Interest Group (SIG) for Liver Diseases in the USA, during the ACVIM Forum in Dallas by Dr. John Cullen, liver pathologists from the North Carolina School of Veterinary Medicine. After discussion with the SIG there was general acceptation of the proposed standards. The discussion was so positive that the American SIG has invited two members of the Liver Standardization Group to give an invited lecture at the ACVIM forum of 2003 (North Carolina) about vascular diseases (Dr. John Cullen), and the Biliary diseases (Dr. Ted van den Ingh), so that the standards will be generally known to the entire field. Later on more speakers of the Liver Standardization group will be invited to present the consensus of the other diseases. The same will be done at the ECVIM congress in Europe, so that both Americans and Europeans will be fully updated about the standardization criteria for hepatobiliary diseases. At the ACVIM forum of 2003 the preliminary consensus for a standard about tumors of the liver and cystic diseases will also be presented for discussion at the more informal evening meeting of the SIG for liver diseases.

The meeting of the WSAVA Liver Standardization Group took place around the discussion microscope of the pathology service in the hospital in Dallas where late President Kennedy spent his last minutes. On this historical ground we discussed the biliary diseases of cats, the intra- and extrahepatic bile tree diseases of dogs, and a start was made with the cystic lesions.

In Munich the group was kindly hosted by prof. Hirschberger and his staff in the laboratory for Clinical Pathology of the Veterinary School. During the ECVIM congress in Munich we have finalized the discussions about feline and canine biliary diseases. This large group of diseases was presented at the Hepatology session of the European Society of Comparative Gastroenterology, in the scientific program of the congress. Dr. Jenny Charles (Australia) presented the standards and definitions of the feline biliary diseases, Dr. Ted van den Ingh (The Netherlands) did the same for the canine biliary disorders. Also in Europe the reactions of the delegates of the congress were unanimously positive and supportive.

In Munich the discussions about standardization of the cystic lesions of the liver and bile system, and of the primary liver and bililiary tumour diseases, were completed. These groups are now ready for presentation at the ACVIM forum of 2003, as mentioned above.

The last and biggest group of diseases are the parenchymal diseases, amongst which different forms of hepatitis, and all diseases in which the liver is affected as result of a metabolic disorder, or in the course of a reaction to septicemia. In Munich we could already prepare for these diseases. It is complex group and requires a very careful description and standardization, because there is much confusion in the literature and amongst clinicians and pathologists about these diseases. In Utrecht, The Netherlands, the parenchymal diseases were conclusively discussed so that all diseases now have a standard description with clear criteria, and also a unified name. Our last meeting was in the Veterinary School of Raleigh (North Carolina, USA) before the 2003 ACVIM Forum, June 2003. Here the concepts for publications were discussed in detail, and the final versions will be completed by the end of August. The publications will be six, one for all but one subgroups (vascular, biliary and cystic, and tumor diseases), two for parenchymal diseases, and one introducing publication explaining backgrounds, methods of approach, etc.

We have found agreement with the Editor-in-Chief of the electronic scientific Journal in the field: Comparative Hepatology. The detailed consensus criteria for the liver and biliary diseases of dogs and cats will be published in this Journal, accompanied by all necessary histological figures to illustrate the typical examples of these diseases. Five publications are foreseen in the coming two years. With this Journal we have also reached agreement about the permission to keep the publication rights for a final joint publication of all standards for liver diseases in a monograph, possibly accompanied by a CD-Rom for all the colour slides of the histology. This monograph in which all standard efforts and descriptions are combined in one volume, can also be expected by the end of 2003.

Finally, I think the group owes a special word of gratitude to two persons who have been crucial. First of all, Dr. Claudio Brovida, President of the WSAVA until October 2002, who had the vision to help this effort become true, which hopefully sets the stage for more world-wide professional cooperations. The veterinary world owes him lasting recognition for his vision, and our specialist group feels it as a privilege to be able to complete the first standardization effort. We are glad you stay involved on behalf of the board of the WSAVA, and know we will also have full support and cooperation of your successor as President, prof. Gabriel Varga. The other word of thank goes to a special member of the Liver Standardization Group, prof. Valeer Desmet from the Medical School of Leuven, Belgium. Prof. Desmet has been engaged with all human liver standardizations over the past 30 years or more, and he can really be considered one of the co-founders of modern human liver pathology. The presence of such a great expert in our group has been and will remain being crucially stimulating. Prof. Desmet is a pure scientist, open for any scientific argument, and he takes active part in the often sharp, hard, but never personal or unfriendly debates about the issues under discussion. It is the strengths of the group that the arguments can be so open and direct, often sharp, always scientific, never personal. And when the veterinarians cannot reach agreement it is always the expert in human pathology who helped to find the way out. We as veterinarians cannot overestimate the value of his contribution which he gives just for free, without any personal compensation.

As conclusion at this stage I think we can be satisfied that the co operations within the group and between the group and the WSAVA, the ACVIM and ECVIM, and the veterinary experts in the field, have worked out so well. Upon finalization of the liver standardization by the end of 2003 we can foresee that there needs to be a continuation of the effort, preferably once every three years, to keep the standards updated and a useful guide to the users in the veterinary world.