The lithotripsy table height: a novel predictor of outcome in shockwave lithotripsy

BACKGROUND: Outcome of Extracorporeal Shockwave Lithotripsy (SWL) is determined by physical factors that affect stone fragmentation and clearance. PURPOSE: To evaluate the predictive value of the Lithotripsy Table Height (LTH) in SWL outcome. Lithotripsy Table Height (LTH) is a variable that represents skin to therapy head distance, and it is proportional to the energy that reaches the stone. MATERIALS AND METHODS: A prospective study enrolled patients undergoing SWL for radiopaque urinary stones. All procedures were performed using a Modulith SLX (Karl Storz, Germany) Lithotripter. Patient weight, height and age; stone location and size; number of shock waves delivered, and LTH were recorded. One month post-procedure a KUB was obtained. Logistic regression analysis was used to evaluate the effects of these variables on stone-free outcome. A ROC curve was plotted. RESULTS: Fifty-six patients were enrolled. After one month follow-up, overall success rate (Stone Free) was 83.9 percent (n = 47). LTH was the only independent predictor of outcome in both univariate and multivariate analysis (p = 0.029). Stone size (p = 0.45) and BMI (p = 0.32) were not significant. In the ROC curve, LTH showed an Area under the Curve = 0.791. Patients with LTH < 218 (n = 8) had relative risk of residual stones = 7.5, odds Ratio: 6.6 (Stone free rate 37.5 percent vs. 91.5 percent). CONCLUSION: LTH appears to be an independent predictor of SWL outcome. High success rates can be expected if LTH > 218. Patients with lower LTH had a less effective therapy, therefore, worse stone fragmentation and clearance. These findings may help improve patient selection for SWL therapy.

Litotripsia extracorpórea a 60 y 120 golpes por minuto: estudio prospectivo randomizado / Extracorporeal shock wave lithotripsy 60 versus 120 shocks per minute: results of a prospective randomized controlled trial

Diversa evidencia sugiere que las litotripsias a menor frecuencia son más eficientes en el tratamiento de las urolitiasis al aumentar la fragmentación en modelos experimentales y en algunas series clínicas. El objetivo de este trabajo es comparar la eficiencia del tratamiento con 60 respecto a 120 golpes por minuto (gpm) en un estudio prospectivo randomizado. Materiales y métodos: Pacientes con litiasis radioopaca, sin tratamiento previo, fueron prospectivamente sometidos a litotripsia a 60gpm (grupo 1) o 120 gpm (grupo 2), en forma randomizada. Se registró la ubicación (renal o ureteral) y tamaño (en mm) del cálculo. Se definió como éxito la ausencia del cálculo tratado al mes de seguimiento, controlado con radiografía simple. En el análisis estadístico se utilizó test chi cuadrado, con intervalo de confianza de 95 por ciento, considerando significativo p<0,05. Resultados: Se trataron 92 pacientes, de los cuales 46 recibieron litotripsia a 60 gpm y 46 a 120 gpm. Ambos grupos no presentan diferencias estadísticas en cuanto a la ubicación y tamaño del cálculo. El éxito global del tratamiento fue de 67,4 por ciento. El grupo 1 presentó mayor éxito (78 por ciento) que el grupo 2 (56 por ciento), siendo diferencias significativas (p=0,0008). En los cálculos renales, el grupo 1 tuvo un éxito de un 70,8 por ciento y el grupo 2 un 58,6 por ciento (p<0,05). En los cálculos ureterales, el grupo 1 tuvo un éxito de un 86,4 por ciento y el grupo 2 un 52,9 por ciento (p<0,05). El número de golpes promedio por litotripsia en el grupo 1 fue de 2326 y en el grupo 2 fue de 2842 (p<0,05). El tiempo requerido para realizar la litotripsia fue mayor en el grupo 1, sin diferencias significativas. Conclusiones: Las litotripsias a bajas frecuencias presentan una mayor efectividad en comparación con las realizadas a mayor frecuencia, requiriendo incluso un menor número de golpes para lograr una fragmentación exitosa, con una duración comparable.

Several experimental and clinical trials have shown that slow rate shock wave lithotripsy (SWL) improves stone fragmentation with a better outcome. The purpose of this trial is to compare the efficiency of slow versus fast rate SWL in a prospective randomized study. Materials and Methods: Previously untreated patients with radiopaque calculi were randomized to undergo treatment with SWL at 60 (group 1) or 120 (group 2) shocks per minute (spm). The location (renal uretheral) and size (mm) of the stone was registered. Treatment success was considered as stone-free patients at one month follow-up with simple x-ray’s. For statistical analysis we used the chi-square test. Results: 92 patients were treated, 46 patients with SWL at 60 spm and 46 at 120 spm. There were significant differences in location and size between both groups. Global treatment success was 67,4 percent. Group 1 had a success rate (78 percent) higher than group 2 (56 percent), that was stadistically significant. In renal stones, group 1 showed a higher success rate (70,8 percent) than group 2 (58,6 percent). In uretheral stones, group showed a higher success rate (86,4 percent) than group 2 (52,9 percent). Both renal and uretheral locations showed statistical difference (p<0,05). The average number of shock waves used in group 1 was 2326 and 2842 group 2 (p<0,05). The time required to complete the SWL was longer in group 1, without statistical difference. Conclusions: Slow rate SWL’s are more efficient than ones performed at fast rates, with a greater success in fragmentation of stones at a lower number of total shock waves, and with a similar treatment time.