However, the ballistic properties of this method of stone fragmentation can be associated with a very high incidence (60%) of proximal stone migration, and this can be exceedingly aggravating for the endourologist.
These researchers in Egypt have performed a very elegant prospective, randomized controlled study of two different ureteral occlusion devices to assess the effectiveness of reducing proximal stone migration, stone-free rates and auxiliary procedures. There were 63 patients in the Stone Cone (Boston Scientific) device group, 59 patients in the N-trap (Cook Urological) device group and 58 patients in the control group. Both of the ureteral occlusion devices significantly improved the incidence of residual stone fragments, ureteral trauma, operative time and need for ureteral stenting compared with the Control group. The patients in the Stone Cone group had a significantly lower incidence of stone migration compared with the other two groups. The stone free rate at 3 weeks was 95%, 83% and 72% for the Stone Cone, N-trap and Control groups, respectively; and this was statistically significantly better for the Stone Cone group compared to the other two groups (p<0.05). The need for auxiliary procedures was 4.76% in the Stone Cone group, 16.94% in the N-trap group and 27.5% in the control group.
While both ureteral occlusion devices significantly reduce residual fragments, the incidence of ureteral wall trauma and need for auxiliary procedures during ureteroscopic pneumatic lithotripsy, the Stone Cone appears to be more effective in preventing proximal stone migration. It would be very interesting to duplicate this study with Holmium laser lithotripsy to determine if these occlusive devices provide the same benefit during retrograde ureteroscopy using this stone fragmentation technique. Of course, the Holmium laser lithotripsy study would need to include groups with varying pulse widths as increasing this variable in the device can significantly reduce the bounce-effect of the Holmium laser lithotripsy on the stone.
Farahat YA, Elbahnasy AE, Elashry OM
Urology. 2011 Jan;77(1):30-5
10.1016/j.urology.2010.05.063
PubMed Abstract
PMID: 20970173
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