The factors that affecting shockwave lithotripsy treatment outcome of kidney stones

Multiple parameters have been individually evaluated to predict shockwave lithotripsy (SWL) outcome. In this study, we analyzed commonly used SWL predictors together to identify the best SWL outcome prediction. The data of patients treated for kidney stones between January 2011 to December 2015 were retrospectively reviewed. The adult patients (≥18 years) with complete data, non-contrast computerized tomography (NCCT) prior to SWL and stone analyses were involved. The patients with urinary system anomaly and taking medications that may affect stone passage such as alpha-blockers or calcium channel blockers and patients with renal dysfunction were excluded. The SWL outcomes were analyzed according to stone localization, stone size, stone burden, stone density on NCCT, body mass index (BMI), stone analysis, skin-to-stone distance (SSD), pararenal-tissue-density (PTD), subcutaneous-tissue-density (STD) and infundibulopelvic-angle (IA). After SWL the patients with clinically insignificant residual fragment (≤3mm) were accepted as success. A total of 124 patients with a mean age 45.08±14.11 were included to the study. The overall SWL success was 72.5 %. The SWL success according to stone localizations were 65.9% in lower pole, 70% in mid zone, 75% in upper pole, 80% in renal pelvis and there was no correlation between localizations and SWL success. The mean BMI was 29.8 and there was no correlation between BMI and SWL success. SWL success were significantly associated with stone size and stone burden (both p=0.0001). The cut-off value of stone size and stone burden were 12.95 mm and 121.38 mm2, respectively. The SSD, PTD, STD and IA were not associated with SWL success. Stone density on NCCT was significantly associated with SWL success (p=0.0001). The cut-off value for stone density was 739 HU. The SWL outcomes of cystine and calcium oxalate monohydrate stones were lower than other stones (p=0.019). In our study, stone size, stone burden and stone density on NCCT has been found as the most important predictors of SWL outcome. Keywords: Shockwave lithotripsy, kidney stones, non-contrast computerized tomography