Experimental study on the friction effect of plastic stent for biliary stone fragmentation (with video)

Abstract

Objectives

In patients with irretrievable or intractable bile duct stone, temporary insertion of plastic stent (PS) followed by further ERCP or surgery has been recommended as a "bridge" therapy. However, the exact mechanism of stone fragmentation has not been discovered. The aim of this study was to evaluate whether PS shape can facilitate stone fragmentation.

Methods

Using a new in vitro bile flow phantom model, we compared the friction effect among the three different PS groups (straight PS group; double pigtail-shaped PS group, and screw-shaped PS group) and the control group. Each group had 10 silicon tube rooms that separately contained one stone and two PS. The control group had 10 rooms each with only a stone and no PS. We performed an analysis of the friction effect by the stone weight and volume changes among the groups, excluding fragmented stones.

Results

After eight weeks, complete fragmentation was noted in one out of 34 cholesterol stones (2.9%), and four out of six pigmented stones (66.7%). They tended to be more prominent in the screw-shaped PS group than them they were in the straight PS group, double pigtail-shaped group, and control group (volume change: -11.33%, 7.94%, 4.43%, and 2.05%, respectively, p=0.1390; weight change: -9.30%, 0.71%, -0.10%, and -1.23%, respectively, p=0.3553).

Conclusion

Stone fragmentation may be induced by PS friction effect. Also, the screw-shaped plastic stents may improve friction effect. These results may help guide future PS development and clinical decisions.

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