In recent years, 8-wire helical basket catheters have emerged as effective tools for
retrieving small common bile duct stones (CBDSs) measuring ≤10 mm [1 ]
[2 ]
[3 ]. Notably, the novel nitinol 8-wire helical basket catheter with a rotation function,
the RASEN2 (Kaneka Corporation), has shown promising results [4 ]
[5 ]. A key feature of this basket is its asymmetrical shape, enabling clockwise or counterclockwise
rotation ([Fig. 1 ]). However, the impact of rotation direction on the treatment of small CBDSs and
debris has not been investigated.
Fig. 1 A novel nitinol 8-wire helical basket catheter with a rotation function (RASEN2; Kaneka
Corporation). Its key feature is its asymmetrical shape, which can be rotated in the
clockwise or counterclockwise direction.
In vitro experiments using the bending bile duct with corner pockets model ([Fig. 2 ]) revealed that counterclockwise rotation exhibited superior efficacy in removing
debris and stones. While sweeping with clockwise rotation, debris was scraped out
by the basket; however, residual debris was significant. On the other hand, during
counterclockwise sweeps, debris scraped by the basket wires was observed to collect
and accumulate within the basket lumen, facilitating en masse removal ([Fig. 3 ]). Although a balloon catheter could release stones lodged in the bile duct flexure
and corner pockets, the 8-wire helical basket with a counterclockwise rotation demonstrated
the ability to retrieve lodged stones even from the corner pocket of the CBD terminus
([Fig. 4 ]).
Fig. 2 The bending bile duct with corner pockets model.
Fig. 3
a, b While sweeping with clockwise rotation, debris was scraped out by the basket; however,
residual debris was significant. c, d While sweeping with counterclockwise rotation, debris scraped out by the basket wire
accumulated within the basket lumen, showing en masse removal.
Fig. 4
a, b The balloon catheter released the stones in the bile duct flexure and the corner
pocket of the CBD terminus. c, d An 8-wire helical basket sweep with counterclockwise rotation could remove the stones,
even those lodged within the corner pocket of the CBD terminus. Abbreviation: CBD,
common bile duct stone.
A 58-year-old patient with small CBDSs underwent endoscopic treatment using RASEN2.
After repeated attempts to remove the stones using clockwise rotation, it was judged
that no further stones could be captured. In contrast, subsequent sweeps with counterclockwise
rotation yielded residual stones that were not retrieved with initial sweeps using
clockwise rotation ([Fig. 5 ], [Video 1 ]). The patient has not experienced recurrent CBDSs since the procedure.
Fig. 5 Subsequent sweeps with anticlockwise rotation to check for residual stones yielded
stones that were missed during the initial clockwise rotation sweeps.
This video shows the impact of rotation direction on the treatment of common bile
duct stones using an asymmetrical 8-wire helical basket.Video 1
These findings underscore the significant impact of rotation direction on the treatment
of CBDSs using the asymmetrical-shaped 8-wire helical basket with a rotation function.
Endoscopy_UCTN_Code_TTT_1AR_2AH
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