Gradual Occlusion of Extrahepatic Portosystemic Shunts in Dogs and Cats Using the Ameroid Constrictor

Abstract

Gradual occlusion of the splenic vein, using a specialized device (ameroid constrictor), was evaluated experimentally in three normal beagle dogs. Splenoportograms were used to verify that total occlusion of the splenic vein had occurred in all dogs within 4 to 5 weeks after application of the device. The ameroid constrictor (AC) was also evaluated as a method of gradual vascular occlusion in 12 dogs and two cats with single, extrahepatic, portosystemic shunts (PSS). Serum bile acid (SBA) concentrations were measured and portal scintigraphy (PS) was performed on all 14 animals preoperatively and 10, 20, 30, and 60 days postoperatively. Two dogs (14%) died from portal hypertension in the early postoperative period. One dog and one cat developed multiple acquired PSS, confirmed by mesenteric portography 90 days after the operation. Portal scintigraphy confirmed total occlusion of the primary shunt in the other 10 animals. Shunt fractions (SF), as measured by PS on postoperative days 30 and 60, declined significantly from preoperative values. Significant decreases were noted between preoperative and postoperative values for preprandial SBA on postoperative day 60 and for postprandial SBA on postoperative day 30. SBA concentrations did not correlate with SF. Based on this study, gradual vascular occlusion using the AC is recommended as a method for treatment of single, extrahepatic, PSS.

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

“…For this reason, some authors have speculated that the AC causes vascular occlusion by a combination of two mechanisms: luminal closure and perivascular inflammation and fibrosis. 11,19,29 This perivascular inflammation and fibrosis may be induced directly by casein or by the formaldehyde that is used in preparation of ameroid clay. 11,30 The minimal luminal constriction of the 5 mm AC achieved during the current 6-week study would suggest that inflammation and fibrosis are likely to be the more important factors contributing to PSS shunt occlusion.…”

“…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. 22 Use of the AC in combination with a portocaval venograft and complete ligation of single intrahepatic PSS was associated with an even higher rate of continued shunting, with multiple extrahepatic shunts being identified in 4 of 8 dogs at long term follow-up.…”

“…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.…”

“…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.…”

Soy Protein Isolate versus Meat‐Based Low‐Protein Diet for Dogs with Congenital Portosystemic Shunts

“…The ameroid constrictor has been shown to result in shorter surgery times and less complication than other surgical approaches. [6][7][8][9] One of the complicating factors is the high anesthetic risk because of central neurotransmitter dysfunction mainly associated with hyperammonemia. [10][11][12] Decreased production of clotting factors causes coagulopathy as an additional risk factor at surgery.…”