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Ito H.,Ohguchi East General Hospital | Ito H.,Yokohama City University | Kuroda S.,Ohguchi East General Hospital | Kawahara T.,Ohguchi East General Hospital | And 3 more authors.
Urolithiasis | Year: 2015

The objective of the study was to evaluate the clinical factors affecting the operative time of flexible ureteroscopy (fURS). We retrospectively evaluated 233 patients with renal stones who had been treated successfully and had stone-free status 3 months after fURS and holmium laser lithotripsy between December 2009 and December 2013 at a single institute. Operative time was divided into three periods (total, before fragmentation, and after starting fragmentation), and associations between possible factors and these periods were analyzed by a multivariate logistic regression model with backward selection. The mean total operative time was 74.0 ± 32.0 min. There were significant differences in the following clinical factors: sex, body height, stone volume, maximum and mean Hounsfield units (HUs), diameter of the ureteral access sheath, and experience of the surgeon, between patients who underwent procedures with a total operative time of less or more than 90 min. A multivariate assessment revealed four independent factors influencing total operative time (P < 0.05): stone volume (P < 0.001), experience of the surgeon (P < 0.001), maximum HUs (P = 0.014), and lack of preoperative stenting (P = 0.027). Larger stone volume, lower experience level of the surgeon, higher HUs, and the absence of preoperative stenting were identified as parameters prolonging the total operative time of fURS and, in particular, the operative time after starting fragmentation. On the other hand, operative time before starting fragmentation, which represented the time required to identify the stone by ureteroscopy and insert the access sheath, was more difficult to predict preoperatively. © 2015, Springer-Verlag Berlin Heidelberg. Source


Ito H.,Yokohama City University | Sakamaki K.,Yokohama City University | Kawahara T.,Yokohama City University | Terao H.,Yokohama City University | And 5 more authors.
BJU International | Year: 2015

Objective To develop and internally validate a preoperative nomogram for predicting stone-free status (SF) after flexible ureteroscopy (fURS) for renal stones, as there is a need to predict the outcome of fURS for the treatment of renal stone disease. Patients and Methods We retrospectively analysed 310 fURS procedures for renal stone removal performed between December 2009 and April 2013. Final outcome of fURS was determined by computed tomography 3 months after the last fURS session. Assessed preoperative factors included stone volume and number, age, sex, presence of hydronephrosis and lower pole calculi, and ureteric stent placement. Multivariate logistic regression analysis with backward selection was used to model the relationship between preoperative factors and SF after fURS. Bootstrapping was used to internally validate the nomogram. Results Five independent predictors of SF after fURS were identified: stone volume (P < 0.001), presence of lower pole calculi (P = 0.001), operator with experience of >50 fURS (P = 0.026), stone number (P = 0.075), and presence of hydronephrosis (P = 0.047). We developed a nomogram to predict SF after fURS using these five preoperative characteristics. Total nomogram score (maximum 25) was derived from summing individual scores of each predictive variable; a high total score was predictive of successful fURS outcome, whereas a low total score was predictive of unsuccessful outcome. The area under the receiver operating characteristics for nomogram predictions was 0.87. Conclusion The nomogram can be used to reliably predict SF based on patient characteristics after fURS treatment of renal stone disease. © 2014 The Authors. BJU International © 2014 BJU International. Source


Ito H.,Ohguchi East General Hospital | Ito H.,Yokohama City University | Kuroda S.,Ohguchi East General Hospital | Kawahara T.,Yokohama City University | And 3 more authors.
International Journal of Urology | Year: 2015

Objective: To investigate factors predicting spontaneous clearance of residual renal fragments after flexible ureteroscopy. Methods: Among 546 patients who underwent lithotripsy with flexible ureteroscopy, 81 had residual renal fragments, as determined by kidney-ureter-bladder films on postoperative day1. The final outcome was determined at 3months after the last flexible ureteroscopy session using non-contrast computed tomography. Patient characteristics and preoperative factors were analyzed using the unpaired t-test and χ2-test. Correlations between the possible predictive factors and the spontaneous clearance of residual renal fragments after flexible ureteroscopy were analyzed using a multivariate logistic regression model with backward selection. Results: Non-contrast computed tomography at postoperative month3 showed that 33 cases (40.7%) had spontaneous clearance of residual renal fragments, whereas 48 (59.3%) showed non-clearance. Significant differences were found between these cases in terms of stone number, stone location, presence of lower pole calculi and preoperative stent placement. Multivariate assessment showed that stone number (P=0.004), presence of lower pole calculi (P=0.021) and presence of hydronephrosis (P=0.024) were independent predictors of the spontaneous clearance of residual renal fragments after flexible ureteroscopy. Conclusions: Stone number, presence of lower pole calculi and presence of hydronephrosis are independent predictive factors of the spontaneous clearance of residual renal fragments after flexible ureteroscopy. © 2015 The Japanese Urological Association. Source


Ito H.,Ohguchi East General Hospital | Ito H.,Yokohama City University | Kawahara T.,Ohguchi East General Hospital | Kawahara T.,Yokohama City University | And 5 more authors.
Journal of Endourology | Year: 2013

Purpose: To investigate the utility and limitations of stone surface area (SA) as a predictor of stone-free (SF) status after a single semirigid ureteroscopy (URS), with or without a flexible component, for the treatment of patients with urinary stones. Patients and Methods: Cases of patients with urinary stones treated by combined URS with holmium laser lithotripsy at a single institute were retrospectively evaluated. Correlations of possible predictors with SF status were analyzed using a logistic regression model. Two types of SA were measured: "Traced stone surface area" (tSA) and "calculated stone surface area" (cSA). Results: According to the univariate analysis, the following variables were significantly associated with non-SF status: Stone number (P<0.001), ureteral stone location (P=0.045), presence of renal stones (P<0.001), tSA (P<0.001), cSA (P<0.001), stone volume (P<0.001), and operator experience (P=0.02). According to multivariate analysis, stone volume (P=0.016) was an independent predictor of SF status. The scatter diagrams for tSA and cSA showed strong correlations between these parameters, and Spearman ρ was 0.975. Conclusions: Stone volume and SA were highly indicative of stone status after single semirigid URS, with or without a flexible component. The formula for cSA, maximum diameter× width×π×1/4, was demonstrated to accurately represent SA in this study. SA, however, indicated a lower clinical priority and utility as a predictor of stone status than stone volume. The combination of semirigid and flexible URS could access any ureteral stones, including those that semirigid URS alone could not treat. The cutoff points for these predictors of outcome were 110.0 mm2 for cSA, 125.0 mm2 for tSA, and 840.0 mm3 for stone volume. © Mary Ann Liebert, Inc. Source


Ito H.,Ohguchi East General Hospital | Ito H.,Yokohama City University | Kawahara T.,Ohguchi East General Hospital | Kawahara T.,Yokohama City University | And 5 more authors.
Urology | Year: 2012

To examine which parameters should be measured to preoperatively determine the stone burden as predictors of stone-free (SF) status after a single flexible ureteroscopy (URS). Although several stone parameters reportedly influence the outcome of treatment for urinary stones, the most reliable indicators of stone burden remain unclear. Patients with renal stones treated by flexible URS with holmium laser lithotripsy between October 2009 and December 2011 at a single institute were retrospectively evaluated. The SF status was determined by kidney-ureter-bladder (KUB) films at postoperative day 1. Correlations of possible predictors with the SF status were analyzed using a logistic regression model. According to the univariate analysis, the following variables were significantly associated with failed treatment: number of stones (P = .001), cumulative stone diameter (CSD) (P < .001), stone surface area (SA) (P < .001), stone volume (P < .001), and presence of lower pole calculi (P = .008). According to the multivariate analysis, the stone volume (P < .001) and the CSD (P = .015) were found to be independent predictors of SF status. The SA (P = .598) had no significant independent influence on the SF status. Among the several parameters regarding the renal stone burden, the stone volume determined by noncontrast computed tomography and the CSD of the KUB were significantly and independently inversely related to the success rate of URS. Among the 3 parameters of stone burden, the SA was found to have a lower clinical utility and priority as a predictor of a SF status after URS. © 2012 Elsevier Inc. All Rights Reserved. Source

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