Tubeless percutaneous nephrolithotomy: yes but when? A multicentre retrospective cohort study.

The aim of our study is to determine the predictive factors for placement of percutaneous nephrostomy tube (PNT) in percutaneous nephrolithotomy (PCNL) procedure and to evaluate the optimal cutoff points of the predictive factors. 229 patients, who had undergone percutaneous nephrolithotomy operation between February 2009 and February 2013 were reviewed retrospectively. Five patients were excluded from the study because of solitary kidney. All characteristics of 224 patients, stones and operative data were investigated. Patient and stone-related factors, such as age, BMI, history of previous surgery or SWL, characteristics of the stone, renal parenchymal thickness (RPT), as well as procedural factors, such as percutaneous access number and location were analyzed by univariate and multivariate tests. The continuous variables were analyzed using Receiver operating characteristic curve analysis. There were no differences in sex, age, BMI and hemoglobin decrease between the groups. Previous operation status, RPT, stone size, multiplicity of the stone, stone localization, blood transfusion presence, access points, access number and operation time were found statistically different according to univariate analysis. Multivariate analysis showed that RPT, operation time and stone size were the independent factors that affected the PNT insertion. For RPT, operation time and stone size, the optimal cutoff points for insertion PNT were 13.75 mm, 75.5 min and 890 mm(2), respectively. Tubeless PCNL should be chosen in patients with stone area less than 890 mm(2), and parenchymal thickness thicker than 13.75 mm and procedure with operation period <75.5 min.