Extracorporeal Shock Wave Lithotripsy for Urinary Tract Stones Using MPL 9000 Spark Gap Technology and Ultrasound Monitoring

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Abstract
Between November 7, 1988 and December 31, 1989, 881 treatments were given with the MPL 9000 lithotriptor to 513 sites in 510 renal units in 464 patients. Of the stones 447 (87.1%) were in the kidney, 64 (12.5%) in the ureter and 2 (0.4%) in the bladder. Stone size was up to 2 cm. in 58.5% of the cases, greater than 2 to 3 cm. in 25.8% and more than 3 cm. in 15.7%, including complete or partial staghorn, or multiple stones. Of the patients 54.2% received only 1 treatment, 17.6% received 2 treatments and 28.2% received more than 2 treatments (re-treatment was necessary in 45.8%). The number of shocks used varied from 610 to 4,000 at 14 to 24 kv., the usual energy used being 18 kv. Of the stones 30.2% were treated after Double-J stents were inserted. A patient was declared stone-free only when no stone particle was visible on a plain abdominal x-ray (or ultrasound if the stone was radiolucent). X-rays 3 months after extracorporeal shock wave lithotripsy (ESWL) were available for review in 397 patients (79.9%) and 72.8% were stone-free (with the aforementioned criteria) at 6 months (61.5% without ancillary procedures and 11.3% after ancillary procedures). Of a subset of 106 patients 84% were stone-free within 3 months when ESWL was restricted to a smaller stone burden, the number of shock waves administered was increased and energy was restricted to 14 to 18 kv. Over-all, 9.1% of the patients needed ancillary measures, including percutaneous nephrostomy in 1.6%, push-back for ESWL in 1.9%, ureterorenoscopy in 5.4%, percutaneous nephrolithotomy in 0.6% and pyelolithotomy/ureterolithotomy in 2.8%. The MPL 9000 device has the unique combination of electrohydraulic shock wave generation and ultrasound monitoring. The latter attribute has the distinct advantage of avoiding radiation to allow for visualization of nonopaque renal and gallbladder calculi. In addition, because there is continuous stone visualization during fragmentation accurate stone targeting can be maintained. The combination of ultrasound monitoring and spark gap technology allows for effective stone fragmentation.