Research Update: Portosystemic shunts in dogs: Can medical therapy allow a delay in surgical intervention?

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Mar 01, 2011


WALTER B. MCKENZIE/GETTY IMAGES
Most recent studies of dogs with congenital portosystemic shunts have investigated the relative efficacy and survival rates of novel surgical interventions. Although medical therapy can be attempted and the relative success at resolution of clinical signs and selected biochemical and histopathologic abnormalities have been compared,1 the survival times of dogs treated with medical therapy vs. dogs treated with surgery have not been compared. If medical management were to result in similar survival times as surgery, then veterinarians could more confidently offer this modality to owners of patients that are unable to tolerate the risks associated with surgery or when expense is a limiting factor. Conversely, differences in survival times may allow owners who are considering avoiding surgery to make more fully informed decisions as to the predicted lifespan of their pets. The authors of a new prospective study of dogs with single portosystemic shunts hypothesized that surgical vs. medical treatment would result in different survival times and that this difference may be influenced by shunt location.

This multicenter study compared short-term outcome and long-term survival of 126 dogs with a single congenital portosystemic shunt and associated clinical signs.2 Treatment options were discussed with each dog owner at the time of diagnosis. Based on the recommendation of the attending clinician and financial considerations, owners ultimately decided whether medical or surgical treatment would be attempted; patients were not randomly distributed into the two treatment groups. Various surgical procedures were used for partial or complete shunt ligation depending on surgeon preference, and these procedures' influence on survival was not evaluated separately. Medical management was not standardized but typically consisted of some combination of oral antibiotics, a modified protein diet, and lactulose.

The final study population included 99 surgically treated dogs and 27 dogs that had been medically managed. Despite the lack of randomization, no statistical differences existed between the two groups in regards to age at diagnosis (which has previously been identified as a prognostic indicator in dogs with portosystemic shunts),3 sex, or the proportion of dogs with intrahepatic or extrahepatic portosystemic shunts. Complete shunt ligation (39.4%) and the placement of ameroid ring constrictors (29.2%) were the most common surgical interventions.

At the time of data collection, 14 of 27 (51.9%) medically managed dogs and 87 of 99 (87.9%) surgically treated dogs were still alive. When considering dogs that had died and those still alive at the time of study termination, survival time was > 3 years for 60% of medically treated dogs and 80% of surgically treated dogs. This difference was significant, with medically treated dogs having a greater likelihood of dying, particularly in the first two or three years after diagnosis, based on Kaplan-Meier survival graphs. The age of the dogs at the time of diagnosis and the shunt location were not significantly associated with survival. Five of 99 (5.1%) surgically treated dogs died of complications secondary to their surgical procedures; however, deaths associated with the portosystemic shunt but unrelated to the surgical procedure were more common in medically treated dogs (8 of 27 [29.6%]) than in surgically treated dogs. Thus, this study's results show that while both surgical and medical management may result in long-term survival in a subset of dogs, surgical treatment is associated with improved survival in the first three years and with overall significantly longer survival times.