Introduction: The clinical symptoms of portosystemic shunts (PSSs) and hepatic microvascular dysplasia (HMD) – portal vein hypoplasia (PVH) in dogs are similar. PSSs are abnormal vascular connections between the portal vein system and systemic veins. HMD is a very rare developmental vascular anomaly, recognisable during histopathological examination. The study aim was to assess the prevalence of HMD–PVH and hepatocellular and vascular pathologies in the liver. Material and Methods: Liver biopsies from 140 dogs (of different breeds and both sexes) arousing clinical suspicion of PSS were examined histopathologically. Results: An initial PSS diagnosis was confirmed in 125 dogs (89.29%). HMD–PVH was found in 12.32% of dogs, as an isolated disease in 9.29%, especially in Yorkshire terriers, and with extrahepatic PSS in 6.67%. Histopathological analysis of muscles around sublobular veins showed that HMD cases presented hypertrophy or hypertrophy with fibrosis. In 2.17% of all dogs with liver vascular developmental disorders calcification was visible around vessels (without correlation by degenerative changes in those vessels), suggesting prior onset of deep metabolic disorders. Clinical suspicion of PSS was also formed upon quite different pathological processes in young dogs. Conclusion: Histopathological findings diagnosed the type of vascular anomalies (PSS or HMD–PVH) or other pathological changes conclusively, therefore detailed hepatic histopathology is an indispensable component of the clinical diagnostic process.
3. Bunch S.E.: Diseases of the liver, bile ducts, and exocrine pancreas. Diseases of the liver and bile ducts of dogs. In: Manual of Small Animal Internal Medicine, edited by R. Lechowski, A. Schollenberger, A. Pomianowski, Wydawnictwo Galaktyka, Łódź, 2008, pp. 373–387.
4. Christiansen J.S., Hottinger H.A., Allen L., Philips L., Aronson L.R.: Hepatic microvascular dysplasia in dogs: a retrospective study of 24 cases (1987–1995). J Am Anim Hosp Assoc 2000, 36, 385–389.
5. Cullen J.M., van den Ingh T.S.G.A.M., Bunch S.E., Rothuizen J., Washabau R.J., Desmet V.J.: Morphological classification of circulatory disorders of the canine and the feline liver. In: WSAVA Standards for clinical and histological diagnosis of canine and feline liver diseases, edited by J. Rothuizen, S.E. Bunch, J.A. Charles, J.M. Cullen, V.J. Desmet, V. Szatmari, D.C. Twedt, T.S.G.A.M. van den Ingh, T. van Winkle, R.J. Washabau, W.B. Saunders Elsevier, Philadelphia, 2006, pp. 41–59.
6. Gabriel A., Miętkiewski J., Ziółkowski A.: Current morphological classification of chronic hepatitis: advantages and disadvantages. Pol J Pathol 1999, 50, 5–11.
7. Gough A., Thomas A.: Breed predispositions to disease in dogs and cats. SIMA WLW, Warsaw, 2006.
8. Hunt G.B.: Effect of breed on anatomy of portosystemic shunts resulting from congenital diseases in dogs and cats: a review of 242 cases. Aust Vet J 2004, 82, 746–749.
9. Johnson S.E.: Hepatic vascular disorders. In: Textbook of veterinary internal medicine. Chronic hepatic disorders. Diseases of the liver and pancreas, edited by S.J. Ettinger, E.C. Feldman, W.B. Saunders Elsevier, Philadelphia, 2000, pp. 1311–1319.
10. Philbey A.W.: More answers needed on congenital portosystemic shunts in dogs and cats. Vet Rec 2013, 172, 360–361.
11. Richter K.P.: Diseases of the liver and hepatobiliary system. In: Handbook of small animal gastroenterology, edited by T.R. Tams, W.B. Saunders Elsevier, St. Louis, 2003, pp. 286–352.
12. Shermerhorn T., Center S.A., Dykes N.L., Rowland P.H., Yeager A.E., Erb H.N., Oberhansley K., Bonda M.: Characterisation of hepatoportal microvascular dysplasia in a kindred of Cairn terriers. I Vet Intern Med 1996, 10, 219–230.
13. Sobczak-Filipiak M., Micuń J., Siedlicki M., Siewruk K., Januchta M., Garncarz M., Galanty M., Lechowski R.: Canine liver pathomorphology evaluated by hepatic biopsy in selected clinical cases. Part I. Życie Weter 2008, 83, 217–219.
14. Sobczak-Filipiak M., Galanty M., Trębacz P., Januchta M., Warchulska K., Fiedorowicz S., Męcik-Kronenberg T.: Hepatic fibrosis in dogs. Życie Weter 2015, 90, 103–105.
15. Sobczak-Filipiak M., Męcik-Kronenberg T., Czopowicz M., Galanty M., Trębacz P., Frymus J., Badurek I., Szarek J.: Lipogranulomas and pigment granulomas in livers of dogs with portosystemic shunt. Pol J Vet Sci 2018, 21, 265–272.
16. Sobczak-Filipiak M., Szarek J., Czopowicz M., Galanty M., Dolka I., Trębacz P., Frymus J., Lechowski R.: The stellate cells in livers of dogs with portal vein hypoperfusion. Med Weter 2018, 74, 392–397.
17. Stalker M.J., Hayes M.A.: Developmental anomalies. Liver and biliary system. In: Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals, edited by M.G. Maxie, W.B. Saunders Elsevier, Philadelphia, 2007, pp. 301–304.
18. Stolarczyk J.: Advances in the diagnosis of chronic hepatitis. Pol J Pathol 1999, 50, 27–30.
19. Warchulska K., Sobczak-Filipiak M., Galanty M.: Hermaphroditism and urolithiasis in a Yorkshire terrier with congenital extrahepatic portosystemic shunts. J Compar Pathol 2014, 150, 115.