Abdelhamid M et al, 2016: A Prospective evaluation of high-resolution computed tomography parameters in predicting shock wave lithotripsy (SWL) success for upper urinary tract calculi.
Abdelhamid M, Mosharafa A, Ibrahim HM, Dogha MM, Selim HM, El Ghoneimy MN Dr, Salem HK, Abdelazim MS, Badawy H.
Department of Urology, Cairo University, Cairo, Egypt.
Department of Urology, Fayoum University, Fayuom, Egypt.
Abstract
OBJECTIVE: To evaluate the ability of non-contrast CT parameters (stone size, stone attenuation, and skin-to-stone distance) to predict the outcome of shock wave lithotripsy (SWL) in a prospective cohort of patients with renal and upper ureteric stones.
PATIENTS AND METHODS: Patients with stones 5-20 mm were prospectively enrolled from 2011 to 2014. Patients had NCCT with recording of stone size, stone mean attenuation, and skin-to-stone distance (SSD), as well as various stone and patient parameters. The numbers of needed sessions as well as the final outcome were determined, with SWL failure defined as residual fragments >3mm. Predictors of SWL failure were assessed by multiple regression analysis. Results 220 Patients (mean ±SD age 41.5 ± 12.4 years) underwent SWL. Mean ±SD stone size was 11.3 ±4.1 mm while mean ±SD stone attenuation was 795.1 ±340.4 HU. Mean ±SD skin-to-stone distance (SSD) was 9.4 ±2.1 cm. The average number of sessions was 1.64. SWL was successful in 186 (84.5%) patients (group A) while 34 (15.5%) patients had significant residual fragments (>3mm). On univariate analysis, predictors of SWL failure included, stone attenuation >1000 HU, older age, higher BMI, higher attenuation value, larger stone size and longer SSD. Increased SSD and higher stone attenuation retained their significance as independent predictors of SWL failure (p˂0.05) on multiple regression analysis both after 1st session and as final SWL outcome. A positive correlation was found between number of SWL sessions and mean stone attenuation (r = 0.6, p<0.001) and SSD (r=4, p<0.001).
CONCLUSIONS: Stone mean attenuation and SSD on non-contrast CT are significant independent predictors of SWL outcome in patients with renal and ureteric stones. These parameters should be included in clinical decision algorithms for patients with urolithiasis. For patients with stones having mean attenuation of >1000 HU and/or large SSDs, alternatives to SWL should be considered.
J Endourol. 2016 Sep 5. [Epub ahead of print]
Comments 1
The Storz Medical Lithotripsy Database contains > 30 abstracts+reviews on this topic. Reading the present paper I did not find any news which will have a significant different impact on the handling of stone patients. “The cut off for stone attenuation predicting failure of SWL varied in various studies and was suggested at 750 HU [8,10], 900 HU [4,9], 950 HU [6], 970 HU [13], and 1000 HU [11,14].”
The use of the term “prospective” is changing. Some authors use it to describe the fact that they planned to evaluate a certain procedure on some patients. Finally they do a retrospective data analysis. I think that the preselection in a study carries a higher bias risk than a regular retrospective study.