Evaluation ofIn VivoBehavior of Ameroid Ring Constrictors in Dogs with Congenital Extrahepatic Portosystemic Shunts Using Computed Tomography

Abstract

Complete shunt occlusion after AC placement is usually dependent on soft tissue reaction. Ameroid constrictors ≥5 mm diameter may not promote complete shunt occlusion.

Determination of Porto‐Azygos Shunt Anatomy in Dogs by Computed Tomography Angiography

“…A preoperative description of the porto‐azygos shunt insertion site facilitates the surgical approach and reduces the duration of the surgery, as well as the risk for continued shunting because of improper selection of the site of attenuation . Porto‐azygos shunts that traverse the diaphragm before entering the azygos vein may have tributaries from gastric veins near the diaphragm …”

In vitro development and evaluation of a polyacrylic acid–silicone device intended for gradual occlusion of portosystemic shunts in dogs and cats

“…Although plasma has been used in some in vitro studies 6,8 involving ameroid ring constrictors, similar results have been achieved when saline (0.9% NaCl) solution was used. Namely, the in vitro results may not have been reflective of the in vivo scenario because of physiologic processes that could not be fully replicated in a laboratory setting.…”

“…[6][7][8]26 The weight of an ameroid ring constrictor (approx 1,400 mg 27 ) has the potential to cause shunt closure by vessel kinking, which may lead to portal hypertension. [6][7][8]26 The weight of an ameroid ring constrictor (approx 1,400 mg 27 ) has the potential to cause shunt closure by vessel kinking, which may lead to portal hypertension.…”

“…6 The rings were measured once per week as described for part 1. Twelve rings were filled with 2 slight variations of formulation 4: 6 of formulation 4A and 6 of formulation 4B.…”

“…3,4 Attenuation can be obtained via acute complete or partial ligation of the shunt or placement of a gradual occlusion device such as an ameroid ring constrictor or cellophane band to surround the shunt. 6,[10][11][12] The optimal period during which surgical closure of a portosystemic shunt should be achieved is unknown. Ameroid ring constrictors swell in vitro but not to complete lumen closure.…”