Evaluation of a portocaval venograft and ameroid ring for the occlusion of intrahepatic portocaval shunts in dogs

OBJECTIVE:To evaluate the use of a portocaval venograft and ameroid constrictor in the surgical management of intrahepatic portosystemic shunts (PSS). STUDY DESIGN: Prospective, clinical study. Animal Population: Ten client-owned dogs with intrahepatic PSS. METHODS: Portal pressure was measured after temporary suture occlusion of the intrahepatic PSS. In dogs with an increase in portal pressure greater than 8 mm Hg, a single extrahepatic portocaval shunt was created using a jugular vein. An ameroid ring was placed around the venograft and the intrahepatic PSS was attenuated. Transcolonic pertechnetate scintigraphy was performed before surgery, 5 days after surgery, and 8 to 10 weeks after surgery. Dogs with continued portosystemic shunting were evaluated further by laparotomy or portography. Clinical outcome and complications were recorded. RESULTS: Mean (+/- SD) portal pressure increased from 6 +/- 3 to 19 +/- 6 mm Hg with PSS occlusion; in all 10 dogs, the increase in portal pressure was greater than 8 mm Hg. There were no intraoperative complications, and, after creation of the portocaval shunt, the intrahepatic PSS could be completely ligated in 8 of 10 dogs. The final portal pressure was 9 +/- 4 mm Hg. Postoperative complications included coagulopathy and death (1 dog), ascites (3 dogs), and incisional discharge (3 dogs). Five of 8 dogs had continued portosystemic shunting at 8 to 10 weeks after surgery. Multiple extrahepatic PSS were demonstrated in 4 of these dogs. Clinical outcome was excellent in all 9 surviving dogs. CONCLUSIONS AND CLINICAL SIGNIFICANCE: The surgical technique resulted in a high incidence of multiple extrahepatic PSS. Short-term clinical results were promising, but long-term outcome must be evaluated further.     

Use of portocaval venografts with ameroid constrictor placement and hepatic lobectomy for treatment of intralobular intrahepatic portocaval shunts in four dogs

Liver lobectomy for complete attenuation of intrahepatic portosystemic shunts appears to be a safe and effective surgical treatment. When the intrahepatic shunt vessel can be definitively palpated within a liver lobe or its presence confirmed portographically, liver lobectomy represents a technically simple and effective method of complete shunt attenuation. To maintain portal pressure at an acceptable value after lobectomy, an extrahepatic portocaval shunt vessel can be created by use of an external jugular vein graft. A second shunt vessel can be created if portal pressure remains increased after placement of 1 shunt. Gradual and safe attenuation of the shunt vessel is achieved by placement of an ameroid constrictor on the extrahepatic graft at the time of the initial surgery.     

Evaluation of the characteristics of venous occlusion after placement of an ameroid constrictor in dogs

OBJECTIVES: To evaluate the mechanism of vascular occlusion after placement of an ameroid constrictor (AC) on a large intra-abdominal vein and document changes in blood flow. STUDY DESIGN: Experimental study. ANIMALS: Six adult dogs. METHODS: Six 6.5 mm ACs were digitally scanned to measure area and circumference of the ameroid and inner lumen before surgery. ACs were surgically positioned around the left common iliac vein (CIV) in each dog. Peri-vascular ultrasonic flow probes were positioned on the left CIV cranial to the AC, and on the right CIV as an internal control. Blood flow measurements were recorded daily until there was no, or prolonged minimal, blood flow, at which time the dogs were euthanatized. Left and right CIVs were removed for histologic evaluation, and the ACs re-scanned to evaluate degree and direction of expansion of the ameroid. RESULTS: Reduction in blood flow occurred within 10 days in all dogs. Three dogs had complete occlusion by day 10 from thrombus formation. One dog damaged the flow probes at 13 days when blood flow was approximately 50% of intra-operative values; the dog was euthanatized at 37 days; there was partial occlusion from thrombosis. Two dogs had persistent low blood flow and occlusion from thrombus formation when euthanatized at 59 and 98 days. There was a significant increase in total AC area and outer circumference, and decrease in luminal area and inner circumference when presurgical and postocclusion measurements were compared. CONCLUSIONS: Vascular occlusion after placement of an AC on a large intra-abdominal vein occurred from thrombus formation. CLINICAL RELEVANCE: A similar pattern of venous occlusion may occur after placement of an AC on a portosystemic shunt, which may lead to both short- and long-term complications associated with portal hypertension.