New antireflux self-expandable metal stent for malignant lower biliary obstruction:In vitroandin vivopreliminary study

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Antireflux plastic biliary stents prevent duodenal biliary reflux and improve the stent patency rate. However, the efficacy of the antireflux valve in a self-expandable metal stent (SEMS) for a malignant biliary obstruction has not been well established. We evaluated the efficacy of a SEMS with an antireflux valve using in vitro flow studies and determined the impact of reducing duodenobiliary reflux on the stent patency rate.


In vitro testing was conducted using a bile perfusion system to evaluate the antegrade and retrograde flow resistance, and to determine the ideal shape for the valve. Then, a prospective case series in humans was conducted with an adequately designed SEMS with an antireflux valve.


During the study period, five patients with an unresectable non-hilar malignant biliary obstruction underwent insertion of a SEMS with an antireflux valve. Placement of the SEMS with anantireflux valve was successful on the first attempt in all patients, and no procedure-related complications occurred. Follow up was obtained in all cases. Serum bilirubin level did not decrease to the normal range within 1 month in four patients. Stent occlusions occurred in all four patients as a result of valve malfunctions due to sludge impaction or a clog. Therefore, the study was terminated early due to unexpected results.


SEMS with an antireflux valve was ineffective in patients with non-hilar malignant biliary obstruction due to limitations on current stent technology.

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