Comparison of 2 lithotripter regarding efficacy / complication rate of kidney and ureteral stones

Patients were stratified according to stone location and stone burden. All treatments with either lithotripter took place under anaesthesia (mostly spinal or epidural, few general) to eliminate pain as a limiting factor for optimal treatment and to keep respiratory movements regular for minimal stone movements. With either lithotripter, treatments were started with a series of 500 shock waves of moderate energy (HM3 with 19kV, SLX-F2 level 7). If the first fluoroscopic control showed no fragmentation, shock wave energy was increased to 21-22 kV or level 9 for HM3 and SLX-F2, respectively. In case of partial stone disintegration after 500 shocks, energy was maintaned in order to prevent unnecessary kidney trauma and progressively decreased (kV by kV / level by level) according to the size of the stone fragments. Treatment was stopped prematurely before the maximally allowed number of shock waves delivered (2500 for kidney stones, 3000 for ureteral stones off the kidney) if the x-ray snap shots didn't allow for the detection of residual fragments. Shocks were delivered heart beat triggered, usually at rates of 70-80 shock waves per minute. Modified lithotripter HM3, Dornier: The electro-hydraulic shock waves are generated between two electrodes in a water-bath. In an attempt to offer patients anaesthesia-free treatment, the original HM3 was modified in the early 90's. The elllipsoid aperture was increased from originally 15.0cm (aperture area of 176cm2) to 17.2cm (aperture area of 232 cm2) to have the shock wave energy distributed over a larger surface at the skin level. With this, shock waves became also more concentrated in the second focal area with higher peak pressures. Therefore, most modified HM3 with a wider ellipsoid were operated with a reduced generator capacity of 40nF, instead of 80nF as with the original ellipsoid. The HM3 lithotripter used for this trial has the bigger ellipsoid (17.2cm), but still the original generator (capacity =80nF). Exact energy measurements have never been performed for the "hybrid" model but it is estimated to deliver a total energy of at least 45mJ in the focal zone. Lithotripter Modulith SLX-F2, Storz Medial: The electro-magnetic shock waves are generated in analogy to a loud-speaker. The source aperture is 30cm (aperture area of 707cm2). Of the two focal zones available, we exclusively used the extended focus (F2). Working with a mean energy level 9, total energy in the focal zone is 150mJ. More than 3 times highter than that of the HM3. Treatment time depends on stone burden and localisation as well as fragmentation. Definitively after 2500 shock waves (kidney) and/or 3000 shock waves (ureter) the treatment has to be finished in order to avoid tissue trauma. The average treatment time is approximately 45-60 minutes. This does not include positioning/monitoring/targegint, which takes another 15-30 minutes.