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Porto systemic shunt (Bichon Frise )
Portosystemic Shunts Bichon Frise At Risk
It has been known for a long time that large dogs tend to have intrahepatic shunts and small dogs
tend to have extrahepatic shunts. A recent study from the UVCS shows that breed has a significant
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: n “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%).” In comparison, for cellophane bands postoperative mortality rate was 5.5%. Serious complications were more common in dogs with intrahepatic shunts than those with extrahepatic shunts (P=0.002). Postligation neurologic dysfunction necessitated treatment in 10% of cases. Postoperative serum bile acid concentrations or results of ammonia tolerance testing showed that 84% were normal and 16% were abnormal.
The above two papers provide solid evidence as to the efficacy of the two main techniques for inducing slow occlusion of shunt vessels. They also allow some comparison between the treatment methods, bearing in mind that they contain a number of uncontrolled variables, such as experience of the surgeon, patient breed, method of postoperative evaluation and duration of follow up. These results indicate that there is little difference in outcomes between the cellophane band and the ameroid constrictor. The cellophane band maybe easier to apply, especially in smaller patients and
those with little room to move around the shunt vessel. Postligation neurological disorder has received a lot of attention in recent years. In general, dogs develop generalized motor seizures or even status epilepticus within the first 3 days after shunt attenuation. The reported incidence of postligation neurological disorder varies, but is somewhere around 5%. Steps taken in our practice to avoid PLND are premedication with 10mg/kg phenobarbitone at induction of anaesthesia and
administration of 5 mg/kg phenobarbitone bid for the first 3 days after surgery. Blood glucose levels are monitored carefully and dogs fed the morning after surgery. Should neurological signs such as disorientation or seizures occur, incremental doses of 5 mg/kg phenobarbitone are given intravenously until a total dose of 30 mg/kg over a 24 hour period is given. Seizure activity is then
controlled with a constant rate infusion of propofol while phenobarbitone levels drop. The survival rate of PLND causing status epilepticus is low, with a high incidence of residual neurological deficits and partial motor seizures. Occasionally, PLND will manifest as twitching or ataxia, in which case the prognosis is generally good. Hunt GB. Effect of breed on anatomy of portosystemic shunts
resulting from congenital diseases in dogs and cats: a review of 242cases. Aust Vet J 2004;82:746-9
 Hardie E. M.; Mehl M. L.; Kyles A. E.; et al. Evaluation of ameroid ring constrictors for treatment for single extrahepatic portosystemic shunts in dogs: 168 cases (1995-2001). J Am Vet Med Assoc 2005;
226:2020-30 Hunt G. B.; Kummeling A.; Tisdall P. L. C.; et al. Outcomes of cellophane banding for congenital portosystemic shunts in 106 dogs and 5 cats. Vet Surg 2004;33: 25-31
Associate Professor Geraldine B Hunt
BVSc, MVetClinStud, PhD, FACVSc, University of Sydney, Australia

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