Outcome after extrahepatic portosystemic shunt ligation in 49 dogs
ABSTRACT To evaluate outcomes after attenuation of extrahepatic portosystemic shunts in dogs using surgical silk.
Case records were reviewed for degree of surgical attenuation, experience of the primary surgeon, perioperative mortality and problems related to persistent portosystemic shunting or shunt ligation. Presence of portosystemic shunting after surgery was evaluated by ammonia tolerance testing, measurement of postprandial serum bile acid, plasma urea and cholesterol concentrations and liver enzyme activity. The influence of age, postocclusion portal pressure, primary surgeon, degree of attenuation and postoperative biochemical findings on the occurrence of postoperative problems was assessed.
The mortality rate was 2.1%. Shunt attenuation was complete in 34% and partial in 66% of dogs. Portal hypertension necessitating ligature removal was encountered in only one dog. Five dogs experienced neurological abnormalities (seizures or ataxia), possibly as a manifestation of 'postligation seizure syndrome'. Postoperative liver function was normal in 78% of dogs, including 70% with partial shunt attenuation. Experience of the surgeon was related positively to outcome after partial attenuation (P = 0.002). Postoperative biochemical evidence of abnormal liver function was the most sensitive predictor of recurrence of clinical signs referable to persistent portosystemic shunting.
In the hands of an experienced surgeon, surgical attenuation of single extrahepatic shunts was safe and effective, even in animals with partial attenuation. Most dogs with biochemical evidence of persistent shunting suffer relapse of clinical signs within 18 months of surgery. Postligation neurological syndromes of variable intensity may be more common than previously thought.
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ABSTRACT: The general aim of this thesis was to identify factors associated with outcome after surgical attenuation of congenital portosystemic shunts (CPSS) in dogs and to clarify underlying mechanisms of postoperative recovery in this disease. Two surgical techniques used for CPSS attenuation, ligation and cellophane banding, were evaluated in 97 and 106 dogs, respectively. Cellophane banding resulted in less short-term complication and mortality rates in dogs with extrahepatic shunts. In intrahepatic shunts, cellophane banding resulted in higher complication and mortality rates than in extrahepatic CPSS. After CPSS ligation, no differences in mortality between dogs with intrahepatic or extrahepatic CPSS were found. With either technique a small proportion of dogs did not recover completely. Surgical technique is apparently not the most important factor that defines long-term outcome. After CPSS ligation, the achieved degree of closure was negatively associated with mortality. In dogs with extrahepatic shunts, both variables were correlated with the diameter of the portal vein. CPSS seems to be not only a disease of an additional abnormal vessel, but also a disease that affects the normal portal vasculature. Unexpectedly, long-term outcome did not depend on the degree of CPSS closure or on portal development at the time of surgery. Because haemorrhage was an important complication after CPSS ligation, haemostasis was evaluated in 34 dogs with a CPSS. These dogs had lower preoperative platelet counts, lower activity of clotting factors II, V, VII, X, an increased activity of factor VIII and a prolonged activated partial thromboplastin time compared to healthy dogs. Immediately after CPSS attenuation, platelet counts and the activity of clotting factors I, II, V, VII, IX, X, and XI were further decreased, and prothrombin time became prolonged. In dogs with complete recovery of shunting, haemostasis was normalized after 6 weeks, in contrast to dogs with persistent shunting. In dogs with CPSS, outcome after shunt attenuation is possibly associated with hepatocyte and portal vein proliferation. Liver size and hepatic growth following surgical attenuation of a CPSS were evaluated in 10 dogs. At 2 months after surgery, median liver size had increased from 18.2 to 28.2 cm3/kg body weight. The intraoperative hepatic expression of 19 genes involved in hepatic and vascular growth and fibrosis was evaluated in 48 dogs with a CPSS in relation to postoperative outcome. Increased mRNA expression of MAT2a (methionine adenosyltransferase 2 alpha) and HGFac (hepatocyte growth factor activator) were associated with good recovery. A model including both genes predicted outcome after CPSS ligation correctly in 75% of the dogs. Low MAT2a may partially explain the poorer prognosis of intrahepatic CPSS compared to extrahepatic CPSS. To identify genes that are differently expressed between dogs with different outcome after CPSS attenuation, microarray analyses were performed in liver tissue of 46 dogs with a CPSS. Sixty-three genes were differently expressed, including several genes that may directly affect postoperative recovery. Further studies are essential to confirm and validate these findings. Clarification of factors that define postoperative outcome may help to predict treatment response and provide additional forms of treatment.
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ABSTRACT: In dogs with congenital portosystemic shunts (CPSS), the ability of the hypoplastic liver to grow is considered important for recovery after surgical shunt attenuation. This study investigated hepatic growth after extrahepatic shunt attenuation in dogs using magnetic resonance imaging (MRI) and computed tomography (CT). Ten client-owned dogs with single extrahepatic CPSS. Abdominal MRI, CT, or both were performed before and 8 days, 1, and 2 months after shunt attenuation. Liver volumes were calculated from the areas of the MRI or CT images. Before surgery, median liver volume was 18.2cm3/kg body weight. Liver volume increased significantly after surgery. Growth was highest between days 0 and 8 and decreased afterward. Median liver volume was 28.8 cm3/kg at 2 months after attenuation. No significant differences in growth were found between dogs with complete or partial shunt closure or between dogs with complete or incomplete metabolic recovery. Volumes measured from consecutively performed MRI and CT images correlated well (r = 0.980), but volumes from MRI images were significantly larger than volumes from CT images (6.8%; P = .008). After shunt attenuation, rapid normalization of liver size was observed. Hepatic growth was not decreased in dogs after partial closure of CPSS or in dogs with subclinical, persistent shunting 2 months after surgery. CT is the preferred imaging method for volumetric estimation because of speed.Journal of Veterinary Internal Medicine 12/2009; 24(1):114-9. DOI:10.1111/j.1939-1676.2009.0439.x · 2.22 Impact Factor
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ABSTRACT: To provide a comprehensive review of the experimental and clinical data related to gradual vascular occlusion of congenital portosystemic shunts (CPS) in dogs. Literature review. PubMed literature search (1966-2004). Surgical intervention and complete vascular occlusion have been recommended for CPS therapy in dogs; however, acute complete ligation of CPS is often associated with life-threatening portal hypertension. Recently, several investigators have attempted to reduce the risk of postoperative portal hypertension by using gradual vascular occlusion. Successful vascular occlusion has been achieved using partial ligation with silk suture, ameroid constrictors, cellophane bands, thrombogenic coils and hydraulic vascular occluders. Objective comparisons of the reliability and rate of vascular occlusion produced by each of these methods have been limited by differences in experimental models and a lack of definitive follow up evaluation in some clinical studies. Gradual vascular occlusion is widely used in the clinical treatment of CPS in dogs. Objective evaluation of the experimental and clinical data on each of the techniques for gradual vascular occlusion is necessary for informed clinical practice and for the planning of future research into this important area. Even from the limited data available, it is clear that the ideal method for gradual vascular occlusion of CPS has yet to be identified.Veterinary Surgery 01/2005; 34(1):83-91. DOI:10.1111/j.1532-950X.2005.00015.x · 0.99 Impact Factor