Experimental Evaluation of Four Methods of Progressive Venous Attenuation in Dogs

Abstract

Both ameroid constrictor implantation and cellophane banding show promise for progressive attenuation of single extrahepatic portosystemic shunts in dogs. Because rapid occlusion was seen with ameroid constrictors, however, cellophane banding maybe a safer technique in animals with increased hepatic vascular resistance. Further evaluation of both treatments in clinical cases is warranted.

Effect of Petrolatum Coating on the Rate of Occlusion of Ameroid Constrictors in the Peritoneal Cavity

“…It has been suggested that PSS occlusion over a 6-week period would be unlikely to cause portal hypertension, based on previous documentation of successful complete ligation of PSS at a second laparotomy within one month after the initial partial ligation. [11][12][13] To this end, investigators have attempted gradual occlusion of PSS by a variety of methods, including cellophane banding, 14,15 intravascular coils, 16 and partial ligation with silk. 17,18 Most recently, ameroid constrictors (AC) have been recommended as an effective device for progressive occlusion of PSS and have gained widespread clinical use in North America.…”

“…8,19,20 Unfortunately, none of these methods of vascular occlusion has been reported to produce reliable complete occlusion over a 6-week period. 11,19 In addition, in two recent studies applying AC to single extrahepatic PSS in dogs and cats, 17% of the animals (17% 19 , 17.5% 21 ) were found to have developed multiple extrahepatic shunts at long term follow-up. 19,21 Another study of clinical results after AC in 24 cats with single extrahepatic PSS reported that 8 of 14 cats (57%) had persistent shunting 8-10 weeks after surgery.…”

“…23 Vascular occlusion is thought to occur by a combination of extraluminal compression and perivascular inflammation and fibrosis. 11 Research of original literature regarding the use of AC revealed that early investigators had coated the rings in petrolatum, thereby delaying water absorption and expansion of the casein ring. 24,25 These studies documented the rate of closure for non-coated (NCA) and petrolatum-coated ameroid constrictors (PCA) when immersed in buffered saline solution and maintained at 381C, demonstrating that petrolatum slowed the rate of expansion by 33% because of decreased hygroscopic capability.…”

Surgical correction of a splenophrenic shunt in a dog: a case report

“…In a study from 1999, the femoral vein was dissected from the surrounding connective tissue without any tissue attachment and fibrosis could be easily stimulated by the cellophane resulting in vessel occlusion (Youmans and Hunt 1999). However, in the case reported here, the shunt vessel was inserted into the central tendon fibres and it was not possible to dissect the shunt without the tendon fibres.…”

“…When portal blood bypasses the hepatic sinusoids, the liver is deprived of hepatotrophic substances including insulin and glucagon, and the systemic circulation and brain are exposed to nonmetabolised intestinal toxins (Youmans and Hunt 1999). Medical management may control hepatic encephalopathy in the short term; however, a progressive deterioration in liver function occurs until shunt occlusion (Worley and Holt 2008).…”