Evaluation of valve function in antireflux biliary metal stents

Abstract

BackgroundTo overcome duodenobiliary reflux induced by biliary stents, antireflux valve (ARV) biliary stents have been developed and showed improvement in stent patency. However, negative study results have also been reported because stent patency may be decreased by the malfunction of ARV itself. Given such mixed results, the true efficacy of ARV remains unknown and the mechanism of its dysfunction needs to be clearly elucidated. The aim of this study was to investigate the exact mechanism of ARV dysfunction using in vitro phantom models.MethodsTwo experimental models were designed to evaluate two important environmental factors suspected to cause ARV malfunction, i.e. bile flow and pH. Three types of ARV metal stents from different companies were used for the experiments: a funnel type ARV, a windsock type ARV, and a wine glass-shaped ARV. Ten stents of each type were tested (five stents in the bile flow phantom model, and another five stents in the duodenal pH environmental model). To determine ARV malfunction, ARV-induced flow resistance was measured using a custom-made testing device. All stents from the two models were removed every 2 weeks for 12 weeks after stent insertion and were evaluated on morphological and functional changes of the ARV.ResultsOnly ARV of wine glass-shaped ARV was morphologically changed due to silicone bond detachment in the bile flow model. All types of ARV were morphologically changed in the pH model. The morphological changes of ARV influenced the flow resistance. The antegrade pressure gradients were increased over time in the pH model (p < 0.05).ConclusionsMorphological change of the ARVs may induce dysfunction of ARV metal stents, which is mainly due to duodenal pH environment. In the future, development of new ARV that is not affected by duodenal environmental factors can be expected to improve stent patency.Electronic supplementary materialThe online version of this article (10.1186/s12876-018-0878-8) contains supplementary material, which is available to authorized users.

Antireflux covered metal stent for nonresectable distal malignant biliary obstruction: Multicenter randomized controlled trial

“…Notably, the researchers conducted a proof‐of‐concept evaluation using barium meal examination and demonstrated a significantly lower rate of duodenobiliary reflux in the ARMS group. Given considerably heterogeneous designs of ARMS and different commercial availability of ARMS across countries, a well‐powered prospective study is required to evaluate a specific type of ARMS.…”

“…Our study lacked preclinical and clinical functional studies for evaluation of the effectiveness of the antireflux valve. 19,22,23 As a result of the nature of the procedures, the physicians involved in the procedures and collection of follow-up data were not blinded to the types of SEMS.…”

“…An antireflux metal stent (ARMS) with a valve against duodenobiliary reflux was developed to mitigate the risk of SEMS dysfunction as a result of duodenobiliary reflux. [17][18][19][20][21][22] Despite different designs of antireflux valves in prior studies, 23 ARMS have generally been associated with lower risks of stent occlusion and non-occlusion cholangitis compared with conventional SEMS. We have evaluated the effectiveness of an ARMS with a funnel-shaped antireflux valve 24 in patients who underwent covered SEMS occlusion as a result of duodenobiliary reflux and, thus, were considered to be at higher risk of recurrent occlusion after a reintervention.…”

Design and evaluation of a novel anti-reflux biliary stent with cone spiral valve

“…As the temperature increased, the crack propagation speed of rubber increased. 41 Kwon et al 19 put forward that the pH environment of the duodenum affects the shape and function of the valve. Therefore, it is necessary to comprehensively consider the working state and use environment of the valve in the following research to optimize the valve structure.…”

“…Furthermore, research methods for anti-reflux biliary stent are single and not rich in view of the fact that mainly focused on in vivo clinical trials and a few of in vitro experiments. 19 Clinical trial has some limitations although it is convincing in some points of view, such as time consuming, uneconomic, limited research results, and many uncontrollable factors which may make the absence of strict control and contrast during research. 7,10 Structural design of anti-reflux valve has a crucial impact on the efficacy of stent.…”