In situ SWL of ureteral stones: comparison between an electrohydraulic and an electromagnetic shockwave source

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

From January 1, 1990, until August 31, 1998, we treated 175 ureteral stones in situ 9 to 252 mm(2) (mean 55.2 mm(2)) 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 mm(2) (mean 47.4 mm(2)). After the introduction of an upgraded electromagnetic shockwave source, the EMSE F150, 33 ureteral stones of 9 to 150 mm(2) (mean 40.1 mm(2)) 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 mm(2) (mean 62.3 mm(2)) were treated in situ. In all series, treatment strategies were identical.

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.

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.