Objective: To produce and validate a predictive model based on computer tomography (CT) parameters for calculating the probability of a stone to be visible in fluoroscopy of shockwave lithotripsy (SWL) and to compare its accuracy to that of kidney-ureter-bladder (KUB) film.
Materials and Methods: We retrospectively analyzed 306 patients (sample group) who underwent an SWL between March 2011 and August 2012. A multivariate analysis of several parameters extracted from preoperative CT scan was conducted in order to identify independent predictors for radiopacity in SWL fluoroscopy. The results were used for the creation of a predictive model. Internal validation was made on a group of 75 patients (validation group) treated from September 2012 until December 2012. Predictive accuracy of the model was evaluated by receiver operating characteristic (ROC) curve and calibration plot. ROC curve was also used for comparing the predictive accuracy of the model to that of KUB.
Results: From 306 evaluated stones, 238 (77.8%) were visible in fluoroscopy. Results of the multivariate analysis revealed that stone size (p< 0.001), stone attenuation (p< 0.001), location in the mid ureter (p< 0.001), the distance between the stone and the anterior abdominal wall (p< 0.001) and fat thickness of the anterior abdominal wall (p=0.001) were all independent predictors for stone radiopacity in fluoroscopy. A predictive model was produced based on the above parameters. The model demonstrated high calibration and areas under the curve of 0.923 and 0.965 in the sample and validation group, respectively while its predictive performance was significantly higher (p< 0.001) of that of KUB (area under the curve=0.727).
Conclusions: This novel model can estimate with high accuracy stone radiopacity in SWL fluoroscopy utilizing parameters of CT scan and thus, it can be used as an alternative to KUB for treatment planning.
Written by:
Sfoungaristos S, Hidas G, Gofrit ON, Yutkin V, Latke A, Landau EH, Pode D, Duvdevani M. Are you the author?
Hadassah Hebrew University Hospital, Urology, Jerusalem, Israel, Jerusalem, Israel, 26500.
Reference: J Endourol. 2014 Aug 8. Epub ahead of print.
doi: 10.1089/end.2014-0190.ECC14
PubMed Abstract
PMID: 25105344