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Does surgical or medical management of extrahepatic portosystemic shunts in dogs carry a better prognosis for the resolution and reduction of neurological dysfunction?
J. Smachlo and W. Gordon-Evans
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PICO question
In dogs with congenital extrahepatic portosystemic shunts that are treated with surgical attenuation what is the persistency, frequency, severity and outcome of neurological signs when compared to dogs that are treated medically?
Clinical bottom line
Category of research question
Prognosis
The number and type of study designs reviewed
Ten papers were critically reviewed
Strength of evidence
Weak
Outcomes reported
For short-term success, owners reported an overall decrease in neurological signs associated with neurological dysfunction and an increase in quality of life after the initiation of either medical management or surgical management. Surgical management has a weak association with higher mortality or severe neurological signs in the immediate postoperative period
Conclusion
It is challenging to make a direct comparison between medical and surgical management but, overall, both strategies seemed to decrease neurological signs in the short term. There was a lack of evidence and available data about the efficacy of each for long-term control of neurological signs
How to apply this evidence in practice
The application of evidence into practice should take into account multiple factors, not limited to: individual clinical expertise, patient’s circumstances and owners’ values, country, location or clinic where you work, the individual case in front of you, the availability of therapies and resources.
Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.
[...]
One of the most common clinical signs for a dog at presentation with an extrahepatic portosystemic shunt (EHPSS) is neurological signs, which can range in severity from mild head pressing and ataxia to seizures. The majority of EHPSSare managed through surgical attenuation, but that is not always an option for owners or achievable due to the anatomy of the shunt. Preoperative neurological signs of hepatic encephalopathy secondary to congenital extrahepatic portosystemic shunt (CEPSS) is caused predominantly by hyperammonemia, which decreases following successful shunt attenuation. The central nervous system may experience chronic astrocyte changes from a CEPSS, which causes an abnormal metabolic environment preoperatively and the sudden change of surgical attenuation favours an excitatory state. Post-attenuation neurological signs (PANS) is suspected to develop post attenuation when a metabolic event occurs in conjunction with the chronic preoperative central nervous system changes. Other contributing factors for dogs developing PANS is unknown, with conflicting evidence about the association of increasing age and shunt attenuation method. Unlike with hepatic encephalopathy, dogs that experience PANS have normal ammonia levels. There were no studies that had a direct comparison between the effectiveness of surgical or medical management of EHPSS in decreasing neurological signs. Overall, Strickland et al. (2018) found the lowest incidence of short-term postoperative neurological signs at 4/126 dogs (3%), while Wallace et al. (2018) found the highest incidence of short-term postoperative neurological signs at 4/14 dogs (29%) and Watson & Herrtage (1998) found an incidence of owner-reported decrease in neurological signs after the initiation of medical management of 3/7 dogs (43%), as well as a reported increase in quality of life.
Favier et al. (2020), Watson & Herrtage (1998), and Strickland et al. (2018) found that the owners reported a decrease in neurological signs and an increase in quality of life after the initiation of medical management. However, these studies lost several dogs in the follow-up period and had relatively small sample sizes. Watson & Herrtage (1998) also evaluated the long-term efficacy of medical management and at 3 years found that only 3/9 dogs (33%) of the dogs included in the follow-up were still alive.
All the studies that evaluated for surgical management found that there was an overall decrease in neurological signs from preoperatively to postoperatively. Worley & Holt (2008) found that 12/17 dogs (71%) in their study displayed preoperative neurological signs, which decreased to 4/17 dogs (24%) after surgical attenuation. However, there was a risk of perioperative mortality or dogs succumbing to refractory seizures with 48 hours postoperatively. For instance, Tisdall et al. (2000) found that with surgical attenuation, the overall proportion of dogs with neurological signs decreased from 70/89 (79%) preoperatively to 11/89 (12%) postoperatively. The majority of the dogs with signs postoperatively had also displayed neurological signs prior to surgery. The study also found that there is a very weak association with the use of phenobarbital to decrease the incidence of postoperative seizures. Only two of the studies evaluated the longer-term efficacy of surgical attenuation in decreasing neurological signs associated with EHPSS. Wallace et al. (2018) had a follow-up ranging from 6 to 72 months postoperatively in nine Pugs with owners reporting no neurological signs or need for medical management. Harvey & Erb (1998) had a 1–10 year follow-up period of eight of the 12 non-encephalopathic dogs, and owners reported the development of no neurological signs. However, both of the longer-term evaluations were based on owner reports, they were small sample sizes, and it is unclear how many dogs actually made it very far into the range of the follow-up period.
The studies suggest that there may be a weak association with higher mortality and/or increased severity of neurological signs that results in euthanasia in the immediate perioperative period for surgical management than after the initiation of medical management. For example, Fryer et al. (2011) had four dogs in the immediate postoperative period that had generalised motor seizures and did not survive to hospital discharge. Similarly, Wallace et al. (2018) found that four of the 14 Pugs were euthanised within 1 month of surgery from continued and/or worsening neurological signs and intractable seizures, and one of the control group dogs died from intractable seizures within 1 month postoperatively. However, although no immediate deaths were reported in either of the studies that addressed medical management, it cannot be ruled out because there is no clearly defined timeline for the dogs’ deaths.
Two of the biggest limitations with these retrospective studies is that many only had very short-term follow-up periods and the data of several dogs were lost in the follow-up period. It was difficult to discern how a dog’s quality of life might be impacted 5 years down the road after the initiation of medical management or postoperatively. Additionally, the owners were predominantly relied upon for accurate observation and reporting of neurological signs in their dogs. However, some neurological signs can be very subtle and might have been missed by the owner.
Further research should include prospective studies that have a clearly defined definition and inclusion criteria for post-attenuation neurological syndrome including blood ammonia and glucose levels postoperatively.
[…]
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About
Affiliation of the authors at the time of publication
CANINE
CONGENITAL EXTRAHEPATIC PORTOSYSTEMIC SHUNT
SURGICAL ATTENUATION
MEDICAL MANAGEMENT
NEUROLOGICAL DYSFUNCTION
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