Login to Access Video or Poster Abstract: MP62-09
Sources of Funding: "None"

Introduction

The Modulith SLK-F2 Electromagnatic lithotripter (Storz Medical AG, Tägerwilen, Switzerland) is the first lithotripter on the market with a unique design that allows for a dual focus system with the option of either a narrow or wide focal zone. Ex vivo data on the SLK-F2 lithotripter shows that disintegration capacity and renal vascular injury are independent of the focal diameter of the SW generator at the same peak positive pressure and disintegration power. The objective of this study is to compare the single-treatment success rates of narrow and wide focal zones for shock wave lithotripsy of renal stones.

Methods

263 patients, with a previously untreated >= 5 mm radio-opaque solitary stone located within the collecting system, were randomized to receive narrow or wide focus lithotripsy, while maintaining a constant overall energy level of 6. Patients were followed with KUB x-rays and renal ultrasound at 2 and 12 weeks post lithotripsy to assess stone area and stone free status. Primary outcome was success rate, defined as stone-free or adequate fragmentation (sand or asymptomatic fragments <=4 mm) at 3 months following a single SWL treatment.

Results

130 patients were randomized to narrow focus lithotripsy versus 133 to wide focus lithotripsy. The groups were similar in baseline characteristics. The overall success rates were statistically different at 2 weeks post treatment (Narrow: 69.2% vs Wide: 57.1%; P = 0.042) and also at 3 months (Narrow: 69.2% vs Wide: 57.1%; P = 0.042). For smaller stones (area < 100 mm2) there was a greater benefit with narrow focus lithotripsy (72.6% vs 60.3%; P=0.05). The SWL retreatment rate for the same stone within 3 months was significantly higher when Wide focus was used (44.4% vs 30.8%; P=0.023). Overall the complication rates were comparable in both groups (Narrow: 23.3% vs Wide: 15.9%; P = 0.135). However, the narrow group required significantly fewer ancillary procedures within the initial 3 month follow-up period (Narrow: 30.8% vs Wide: 42.9 %; P = 0.042).

Conclusions

Narrow focus lithotripsy yields better outcomes than wide focus lithotripsy, particularly for stones < 100 mm2, with lower retreatment rates and without increased in morbidity.

Funding

"None"