Congenital Portosystemic Shunts; Does Size Matter?

Introduction
It has been known for a long time that large dogs tend to have intra- hepatic shunts and small dogs tend to have extrahepatic shunts. A recent study from the UVCS shows that breed has a signifi- cant influence on shunt anatomy in dogs. Breeds that were significantly over-represented included the Maltese, Silky Terrier, Australian Cattle Dog, Bichon Frise, Shih Tzu, Miniature Schnauzer, Border Collie, Jack Russell Terrier, Irish Wolfhound and Himalayan cat. Bichon Frise with shunts were significantly more likely to be female than male (12:2, P<0.001). Two hundred and fourteen dogs (91.4%), and all cats, had shunts that were amenable to attenuation. Inoperable shunts occurred in 19 dogs (8.2%). Fifty six of 61 (92%) operable shunts in large breed dogs were intrahepatic, versus 10/153 (7%) in small breeds (P<0.0001). Breeds that were not predisposed to portosystemic shunts were significantly more likely to have unusual or inoperable shunts than dogs from predisposed breeds (29% versus 7.6%, P<0.0001). No significant relationship between breed and shunt type could be determined in cats. The conclusions drawn were that animals presenting with signs of portosystemic shunting may suffer from a wide range of operable or inoperable conditions. Veterinarians should be aware that unusual or inoperable shunts are much more likely to occur in breeds that are not predisposed to congenital portosystemic shunts.

Treatment for congenital portosystemic shunts has focused recently on methods for slow attenuation. Two recent publications have outlined the results for cellophane banding and ameroid constrictor placement.

Results for the ameroid ring constrictor were as follows: “Postoperative complications developed in 10% of dogs. Postoperative mortality rate was 7.1%.Twenty-one percent of dogs in which portal scintigraphy was performed 6 to 10 weeks after surgery had continued shunting. Clinical outcome in 108 dogs was classified as excellent (80%), good (14%), or poor (6%).” [...]