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


VETERINARY MEDICINE


COMMENTARY

Although not systematically studied, the presumptive reasons for the referral of dogs with portosystemic shunts are likely multifactorial, including the need for intensive management of severe preoperative hepatic encephalopathy, the technical expertise required for surgical correction, and the fear of severe complications during the immediate postoperative period. It is possible that based on the expense associated with these management and surgical considerations some dogs are euthanized rather than being referred for surgery. This study's results provide owners and veterinarians additional information on the expected short- and long-term survival of medically managed dogs. Although surgery was definitively associated with a longer survival time after diagnosis, a median survival time > 3 years was still achieved in many dogs with medical therapy alone.

In this study, the authors failed to find that a dog's age at the time of diagnosis affected survival, which had been shown to be important in a previous publication specifically evaluating medically managed dogs.3 Based on this finding, the authors conclude that surgical intervention could potentially be delayed in some dogs in favor of medical therapy if circumstances do not allow for immediate referral. However, this conclusion requires further study. In this study, most dogs underwent surgical intervention immediately after diagnosis rather than after a delayed period associated with medical management. Future studies should compare the survival times associated with immediate vs. delayed surgical intervention before veterinarians confidently recommend that owners can attempt medical therapy without later consequences.

The authors acknowledge that their nonrandomized study design may have led to marked bias and, therefore, potentially inaccurate results. As mentioned, clients were allowed to select the final treatment plan for their dogs, and recommendations made by the various surgeons were likely influenced by their personal success with surgical vs. medical therapy of portosystemic shunts, the severity of clinical signs in each particular dog, and the shunt location. For example, it is possible that dogs presenting with more severe hepatic encephalopathy were more likely to be considered poor surgical candidates by some surgeons or, conversely, would have been considered less amenable to medical therapy because of residual clinical signs. It is also possible that in those dogs in which surgery was not selected because of financial reasons, poor compliance with medication due to cost may have influenced survival times or willingness to aggressively manage patients that required occasional hospitalization because of worsening clinical signs. Finally, because only dogs with clinical signs were included in this study,2 whether the long-term survival of asymptomatic patients likewise differs depending on the method of treatment is unknown.

Ultimately, despite the bias involved in patient selection, these conclusions are encouraging for recommending medical management in cases in which surgical intervention cannot be immediately—or ever—considered. Owners should be informed that survival beyond three years occurs in more than 50% of cases, but median survival (time until death of 50% of patients) or effect on true long-term survival is still unknown. A dog's quality of life during this period, meaning persistence of clinical signs due to hepatic encephalopathy, may still be worse than in surgically treated dogs and is ultimately unknown. The reasons why medical management is associated with shorter long-term survival were not investigated but are likely associated with previous authors' findings that although medical management can be equally effective at controlling clinical signs of hepatic encephalopathy and correcting some or all biochemical abnormalities, progressive hepatic fibrosis occurs in dogs that do not undergo surgical correction.1

Greenhalgh SN, Dunning MD, McKinley TJ, et al. Comparison of survival after surgical or medical treatment in dogs with a congenital portosystemic shunt. 2010;236(11):1215-1220.

The information in "Research Updates" was provided by Scott Owens, DVM, and Barrak Pressler, DVM, PhD, DACVIM, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Purdue University, West Lafayette, IN 47907.

REFERENCES

1. Faverzani S, Trombetta R, Grieco V, et al. Clinical, laboratory, ultrasonographic and histopathological findings in dogs affected by portosystemic shunts, following surgery or medical treatment. Vet Res Commun 2003;27 Suppl 1:755-758.

2. Greenhalgh SN, Jeffery ND. Author response to: Willard M. Requests clarification on study of congenital portosystemic shunts. J Am Vet Med Assoc 2010;237(6):624.

3. Watson PJ, Herrtage ME. Medical management of congenital portosystemic shunts in 27 dogs—a retrospective study. J Small Anim Pract 1998;39(2):62-68.


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Source: VETERINARY MEDICINE,
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