New Antireflux Self-expandable Metal Stent for Malignant Lower Biliary Obstruction: in Vitro and in Vivo Preliminary Study

Aim: 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.

Methods: 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.

Results: 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 antireflux 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.

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