Purpose: Kidney stones movement with respiration may cause the displacement of the focus area of stones. The imprecise positioning of stones may affect the effect of traditional extracorporeal shock wave lithotripsy (ESWL). In this study, we prospectively compared three ESWL models of conventional periodical firing, real-time ultrasound imaging of auto-aimed and auto-tracking firing, whether these models affect outcome of renal calculus and reduced renal damage.

Material and Methods: From December 2013 to December 2015, total 102 of 150 patients of single kidney stone of 0.5 to 2cm were enrolled in this institutional review board (IRB) approved trial. We used fluoroscopy and ultrasound imaging for kidney stone localization and focusing first. After the stone was focused and displayed clearly by ultrasound, the ultrasound-based real-time auto-aimed or auto-tracking model were applied for stone monitoring and shockwave trigger control. There were 33, 34 and 35 patients respectively randomized into 3 groups of the periodical firing, auto-aimed, and auto-tracking models with LITEMED LM-9200 ELMA lithotripter undergoing ESWL which were all settled at a rate of 90 per minute and escalating strategy of 500 shocks at 14kV, and 2,500 shocks at 18 kV. Abdominal x-ray follow up to determine the stone-free rate (<5mm) at 1 week and 1 month after ESWL. Voided urine was analyzed before, immediately after and 1 week after ESWL to evaluate renal damage.

Results: The preoperative (pre-op) average stone size respectively of the auto-aimed, auto-tracking and periodical firing models was 9.3 ± 3.6 mm, 10.5 ± 3.2 mm and 10 ± 3.7 mm, There were no statistically significant difference of age, stone size and renal function between groups. The postoperative (post-op) stone size of one week follow-up was 6.8 ± 4.3mm, 8.4 ± 3.3mm and 6.6 ± 4.8mm, and of one month was 5.0 ± 5.5mm, 6.9 ± 4.7mm and 5.4 ± 4.6mm respectively of the auto-aimed, auto-tracking and periodical firing models.

Stone-free rate of auto-aimed, auto-tracking and periodical group is 17 (48.6%), 9 (26.5%) and 14 (42.4%) (p = 0.07) a week later; 20 (57.1%), 11 (32.4%) and 14 (42.4%) (p = 0.036) after one month follow up. The average operation time is 56.1, 44.5 and 39.9 minutes respectively of 3 groups. There was no serious complications in these group caused by the clinical trial. Auto-aimed, auto-tracking and periodical groups appeared pain to emergency department was 1 (2.9%), 2 (5.9%), 2 (6%) patients, and three group post-op urinalysis appeared microscopic hematuria is 18 (51.4%), 11 (32.4%), 12 (36.3%). Three group post-op appeared must receive repeat ESWL respectively is 3 (8.6%), 9 (26.4%), 7 (21.2%) patients.

Conclusion: This prospective, randomized study shows that an auto-aimed model produce better stone-free rate but it may take longer ESWL operation time of kidney stone ranging from 0.5 to 2.0 cm. The auto-aimed model of ESWL can accurately locate and improve traditional percussion effects of ESWL and reducing renal damage.

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Published on 04/10/16

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