The Dretler stone cone: a device to prevent ureteral stone migration-the initial clinical experience

Retrograde stone migration during ureteroscopic lithotripsy occurs in 5% to 40% of proximal and distal ureteral stone cases. This migration increases morbidity and the need for auxiliary procedures. The Dretler stone cone (Medsource, Norwell, Massachusetts) is a novel device to prevent proximal stone migration and facilitate fragment extraction during ureteroscopic lithotripsy. We assessed the safety and efficacy of the Dretler stone cone in the clinical setting and compared it prospectively with a conventional flat wire basket during ureteroscopy for ureteral calculi.

To our knowledge we report the initial clinical use of the Dretler stone cone in 50 consecutive patients with ureteral calculi undergoing ureteroscopic extraction. Calculi were situated above the sacroiliac joint in 24 cases, over the sacroiliac joint in 15 and below the sacroiliac joint in 11. Pneumatic lithotripsy was done in 42 cases. In the remaining 8 cases ureteroscopic (3) or fluoroscopic (5) intact stone extraction was performed. The later 23 cases using the Dretler stone cone were prospectively compared with 20 of ureteroscopic intracorporeal lithotripsy using a standard flat wire basket.

The Dretler stone cone was successfully placed in all 50 cases. In 41 patients it was placed via cystoscopy under fluoroscopic guidance, while 9 impacted stones required ureteroscopic placement. Six patients in whom the Dretler stone cone was used had residual fragments less than 3 mm. No patient required auxiliary procedures. In the prospective trial no patients in Dretler stone cone group had residual fragments greater than 3 mm. or required auxiliary procedures. However, in the flat wire basket group residual stones greater than 3 mm. were present in 6 cases (30%, p <0.001), while auxiliary procedures were required in 4 (20%, p <0.01).

The Dretler stone cone represents a new generation of basketry that minimizes proximal ureteral stone migration and allows safe extraction of fragments during ureteroscopic lithotripsy. In our experience it is associated with a lower incidence of significant residual fragments and fewer auxiliary procedures than conventional flat wire baskets.