Factors affecting fluoroscopy time during percutaneous nephrolithotomy: Impact of stone volume distribution in renal collecting system.

Purpose: To identify the factors increased fluoroscopy time during percutaneous nephrolithotomy and investigate the relationship between the 3D segmentation volume ratio of stone to renal collecting system and fluoroscopy time.

Materials And Methods: Data from 102 patients who underwent percutaneous nephrolithotomy were analyzed retrospectively. Volume segmentation of both the renal collecting system and stones were obtained from 3D segmentation software with the images on CT data. Analyzed stone volume (ASV), renal collecting system volume (RCSV) measured and the ASV-to-RCSV ratio was calculated. Several parameters were evaluated for their predictive ability with regard to fl uoroscopy time.

Results: The stone-free rate was 55.9% after the percutaneous nephrolithotomy. Complications occurred in 31(30.4%) patients. The mean fluoroscopy time was 199.4±151.1 seconds. The fl uoroscopy time was significantly associated with the ASV-to-RCSV ratio (p<0.001, r=0.614). The single tract was used in 77 ( 75.5%) cases while multiple tracts were used in 25 (24.5%) cases. Fluoroscopy time was significantly associated with multiple access (p<0.001, r=0.689). On univariate linear regression analysis, longer fluoroscopy time was related with increased stone size, increased stone volume, increased number of access, increased calyx number with stone, increased ASV-to-RCSV, increased operative time and decreased stone essence. On multivariate linear regression analysis, the number of access and the ASV-to-RCSV were independent predictors of fluoroscopy time during percutaneous nephrolithotomy.

Conclusions: The distribution of the stone burden volume in the pelvicalyceal system is a significant predictor for prolonged fluoroscopy time during percutaneous nephrolithotomy. Measures to decrease FT could be benefi cial in patients with a high ASV-to-RCSV ratio for precise preoperative planning.