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More answers needed on congenital portosystemic shunts in dogs and cats
  1. Adrian W. Philbey, BVSc, PhD, MANZCVSc, MRCVS
  1. Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Edinburgh EH25 9RG, UK
  1. e-mail: adrian.philbey{at}

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SINGLE intrahepatic congenital portosystemic shunts (CPSS) in dogs and cats are usually a consequence of defective closure of the ductus venosus, while extrahepatic CPSS are associated with developmental abnormalities resulting in aberrant connections between the embryonic cardinal and vitelline systems (van Steenbeek and others 2012). Factors involved in closure of the ductus venosus after birth are unknown in most domestic species, but are likely to include haemodynamic changes related to reduced umbilical venous flow, along with mediators of smooth muscle contraction, such as endothelin and thromboxane A2 (Adeagbo and others 2004). Intrahepatic CPSS are more frequent in large breed dogs, whereas extrahepatic CPSS are more frequent in small breed dogs and clinically significant CPSS were diagnosed in 0.18 per cent of dogs admitted to a veterinary teaching hospital (Tobias and Rohrbach 2003). Cats develop both types of shunts, although single extrahepatic CPSS are most frequent in this species (Berger and others 1986).

CPSS result in microhepatica and altered morphology of the liver at the histological level. Histopathological examination is useful for confirming the presence of microscopic changes consistent with CPSS, but biopsies are often taken at the time of surgery for correction of the CPSS and, therefore, are not always available to guide clinical decisions leading up to surgery. An appreciation of the anatomical and pathological features of CPSS at gross and microscopic levels is important for diagnostic investigation and in guiding approaches to treatment. Recent advances in our …

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