By Liesel van der Merwe BVSc MMedVet (Med)
Greenhalgh SN, Reeve JA, Johnstone T et al. 2014. Long-term survival and quality of life in dogs with clinical signs associated with a congenital portosystemic shunt after surgical or medical treatment. Journal of the Veterinary Medical Association Vol 245:527-533
Why they did it
Congenital portosystemic shunts (CPSS) in dogs can be managed surgically, using various techniques, as well as medically with a combination of dietary changes and drug administration. It has long been assumed that surgical correction is preferred as it has the theoretical ability to restore normal physiology. The authors wanted to evaluate if the choice of medical or surgical management affected patient survival rate and quality of life.
What they did
The prospective study included patients with clinical signs attributable to CPSS confirmed as having a portosystemic shunt by either ultrasonography, portovenography or exploratory laparotomy. Selection of treatment method was made by the owner based on discussions with the attending clinician and was thus not randomised. Despite this the two groups were evenly balanced with regards to type of shunt and signalment. All dogs underwent medical stabilisation (dietary, antimicrobial and synthetic disaccharide) for an initial 3 week period. Thereafter medically managed dogs continued to receive a combination of therapies to control their gastrointestinal, neurological and urinary tract clinical signs. For dogs undergoing surgery: cellophane band, ameroid constrictor or ligature methods were used according to surgeon preference.
Owners completed questionnaires at time of entry into the study and periodically thereafter. Recruitment was between June 2002 – Oct 2007 and animals remained in the study for a period up to 10 years (3650 days).
What they found
The final study population comprised of 124 dogs – extrahepatic CPSS was diagnosed in 110 and intrahepatic CPSS in 14 dogs. Of the 124 dogs, 97 (78%) were treated surgically [ligation (39), ameroid constrictor (29), partial ligation (24) and cellophane band (5)] and 27 (22%) were treated medically. The median (ie time taken to get to middle patient (# 62) in the group – not average) follow-up period was 1 936 days. Forty-five dogs died or were euthanased during the study period (0 – 3 323 days, median 759 days). Cause of death was not determined in most cases so may not have been from CPSS causes, but this does not affect the validity of the evaluation of the endpoint.
Median survival in the medically treated group was 836 days, 89% died during the follow-up period of 10 years. Only 22% of the surgically treated dogs died and the median survival could not be measured as the majority were still alive at the end of the study. Only 5 of 97 dogs died in the post-operative period, one after a second surgery. Survival of the surgically treated dogs was significantly (p=<0.001) greater then dogs which underwent medical treatment. Age at diagnosis and shunt type did not significantly affect survival. Shunting fraction was not assessed as a variable.
Surgical treatment of CPSS in dogs resulted in significantly improved survival and lower frequency of ongoing signs compared with medical management. Survival was not affected by age at diagnosis, thus there is no evidence that surgery has to be performed early in life to be effective.