Ureteric retrieval net: comparison with stone extraction by Dormia baskets in an in vitro porcine model

To develop a ureteric retrieval net with advantages over existing stone retrieval methods.

In vitro experimental trials comparing the ureteric retrieval net with Dormia baskets were performed with porcine ureters and artificial calculi placed in a proximal or distal position.

For removing a single, large stone (9 x 6 x 5 mm) the net was slightly better than baskets (100% versus 90%) and it was significantly (P < 0.001) more effective for removing multiple small stones (2 x 2 x 3 mm to 5 x 4 x 3 mm) in one pass (76% versus 40% with three distal stones; 73% versus 13% with three proximal stones; and 53% versus 3% with six proximal stones).

This newly developed ureteric retrieval net has a compact design, resulting in minimal resistance during retraction. Its smooth hydrophilic outer surface enhances scooping properties against the luminal wall. The mesh is similar to that in nylon stockings--porous enough to allow flow, yet small enough to capture fragments. It can capture numerous small fragments with one scoop, but can easily disengage them if extraction is not possible. The loop encompasses the entire lumen with the 'pusher' offset to a side wall, allowing maximal space and visualization, and the device can dilate the ureter to facilitate extraction. Clinical studies are in progress to evaluate the full potential of this new device.