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Abstract

We would like to thank Hamada et al for their interest in our article and for their comments. The major differences between our study1Lee Y.N. Moon J.H. Choi H.J. et al.Effectiveness of a newly designed anti-reflux valve metal stent to reduce duodenobiliary reflux in patients with unresectable distal malignant biliary obstruction: a randomized controlled pilot study (with videos).Gastrointest Endosc. 2016; 83: 404-412Abstract Full Text Full Text PDF PubMed Scopus (50) Google Scholar and previous studies of metal stents with an antireflux function2Hu B. Wang T.T. Wu J. et al.Antireflux stents to reduce the risk of cholangitis in patients with malignant biliary strictures: a randomized trial.Endoscopy. 2014; 46: 120-126Crossref PubMed Scopus (57) Google Scholar, 3Hamada T. Isayama H. Nakai Y. et al.Novel antireflux covered metal stent for recurrent occlusion of biliary metal stents: a pilot study.Dig Endosc. 2014; 26: 264-269Crossref PubMed Scopus (30) Google Scholar, 4Kim D.U. Kwon C.I. Kang D.H. et al.New antireflux self-expandable metal stent for malignant lower biliary obstruction: in vitro and in vivo preliminary study.Dig Endosc. 2013; 25: 60-66Crossref PubMed Scopus (38) Google Scholar, 5Lee K.J. Chung M.J. Park J.Y. et al.Clinical advantages of a metal stent with an S-shaped anti-reflux valve in malignant biliary obstruction.Dig Endosc. 2013; 25: 308-312Crossref PubMed Scopus (28) Google Scholar were that a self-expandable metal stent (SEMS) with a longer valve length (18-20 mm) was used, and a barium meal examination for confirmation of duodenobiliary reflux was performed after biliary drainage in all patients. The newly developed SEMS with an antireflux valve (ARV) showed superior stent patency duration compared with the conventional covered SEMS (cSEMS), and duodenobiliary reflux was an independent risk factor for the development of stent dysfunction. Hamada et al are concerned with the possibility of inhibition of antegrade bile flow by the longer valve portion of the new ARV metal stent (ARVMS). Indeed, the length of the valve portion is one of the most important factors optimizing its function. A short valve may reduce efficacy in terms of prevention of duodenobiliary reflux, and an overly long valve may inhibit antegrade bile flow and delay the resolution of jaundice.3Hamada T. Isayama H. Nakai Y. et al.Novel antireflux covered metal stent for recurrent occlusion of biliary metal stents: a pilot study.Dig Endosc. 2014; 26: 264-269Crossref PubMed Scopus (30) Google Scholar In addition, even if the length of the valve portion does not affect antegrade bile flow, installing a long valve inside the introducer without creasing, complete deployment of the valve, or both, is technically difficult. For this reason, we examined valves 15-mm to 25-mm long in vitro during the development of the new ARVMS. A valve 18-mm to 20-mm long showed the greatest efficacy in terms of preventing duodenobiliary reflux without inhibiting antegrade bile flow. In addition, the delivery system was modified by the use of a novel expandable metal stent as a “bumper” to ensure safe deployment of the valve. The median decrease in bilirubin level (mg/dL) 7 days after stent insertion was not significantly different between the ARVMS and cSEMS groups (1.9 vs 2.6, P = .370), and technical success was achieved in all patients. Although the new ARVMS showed superior stent patency duration and reduced duodenobiliary reflux, ARVMS placement did not reduce overall stent dysfunction or survival in our multivariate analysis. We performed another multivariate analysis for risk factors of stent dysfunction. Apart from complete duodenobiliary reflux as suggested by Hamada et al, the type of stent (cSEMS vs ARVMS) showed borderline statistical significance (P = .055). This result suggests the need for further randomized controlled studies involving large cohorts to confirm the ability of the new ARVMS to improve stent patency. Moreover, efforts should be made to develop an optimal ARVMS that effectively prevents duodenobiliary reflux without affecting other functions of SEMSs. Against duodenobiliary reflux: implications from a randomized controlled trialGastrointestinal EndoscopyVol. 83Issue 3PreviewWe read with great interest the article by Lee et al1 on the superiority of an antireflux valve metal stent (ARVMS) over a conventional covered self-expandable metal stent (SEMS) for distal malignant biliary obstruction. The duodenobiliary reflux is a well-recognized contributor to covered SEMS dysfunction,2-4 and ARVMSs have been expected to be a reasonable treatment option. Full-Text PDF