In Situ SWL of Ureteral Stones: Comparison Between an Electrohydraulic and an Electromagnetic Shockwave Source

Abstract

Purpose:

To compare the influence of different shockwave emitters on treatment efficacy for SWL of ureteral stones in situ.

Patients and Methods:

From January 1, 1990, until August 31, 1998, we treated 175 ureteral stones in situ 9 to 252 mm² (mean 55.2 mm²) using X-ray targeting on a Dornier MPL 9000 X lithotripter, a spark gap machine. From February 1996 through December 1997, we operated a Dornier Lithotripter S equipped with a conventional electromagnetic shockwave source, the EMSE 220. The size of the 71 treated ureteral stones at all levels ranged from 6 to 276 mm² (mean 47.4 mm²). After the introduction of an upgraded electromagnetic shockwave source, the EMSE F150, 33 ureteral stones of 9 to 150 mm² (mean 40.1 mm²) were treated in situ. After a second upgrade, to the more powerful EMSE F150-P, 50 ureteral stones ranging in size from 16 to 345 mm² (mean 62.3 mm²) were treated in situ. In all series, treatment strategies were identical.

Results:

In the first series, auxiliary procedures were performed in 2.3% pre-SWL and 25.1% post-SWL (total 27.4%). The retreatment rate was 23.4%, bringing the effectiveness quotient (EQ) to 67.3. In the second series, the auxiliary procedure rate was 2.8% pre-SWL and 22.5% post-SWL (total 25.3%). The retreatment rate was 19.7%, and the EQ was 70.3. In the third series, auxiliary procedures were performed in 3.0% pre-SWL and 24.2% post-SWL (total 27.2%). The retreatment rate was 18.2% and the EQ 70.2. In the most recent series, no auxiliary procedures were needed before SWL, the post-SWL auxiliary procedure rate was 22%, and the retreatment rate was 10.0%, for an EQ of 75.8.

Conclusion:

The significant improvement in EQ with the EMSE F150-P must be attributed to an improved shockwave source, contradicting the myth that a spark gap source is by definition superior to an electromagnetic one.