In-vitro comparison of different slice thicknesses and kernel settings for measurement of urinary stone size by computed tomography.

Non-contrast enhanced computed tomography (NCCT) is widely used measuring stone size in patients with urolithiasis. We performed an evaluation of the accuracy of stone size measuring via NCCT. In an in-vitro study, we analyzed a total of 38 uric acid and 38 phantom stones. Within NCCT, we used different slice thicknesses (1.5 mm, 2.0 mm, and 3.0 mm) and kernel settings (bone and soft-tissue window). Maximal height, maximal length, and maximal width of each stone were measured on a picture archiving and communication system workstation. Blinded to these results, a second physician measured stone size in the same way using a caliper (real stone size). We used the Bland-Altman method for the analysis of agreement between the two measuring methods. The limit of agreement that was deemed clinical insignificant was ± 1.0 mm. All measurements via NCCT correlated significantly with the real stone size (p < 0.001). This was more pronounced for bone window and smaller slice thickness. Bland-Altman plots showed limits of agreement that exceeded the a priori defined level for all types of measurement with bone window and small slice thickness (1.5 mm) being better than soft-tissue window and large slice thickness (3.0 mm). We conclude that stone size measurement by NCCT with established settings is not exact. Stone size can easily be over- or underestimated by several millimeters. Using bone window and small slice thickness leads to more accurate results.

Uncovering the real outcomes of active renal stone treatment by utilizing non-contrast computer tomography: a systematic review of the current literature.

PURPOSE: To evaluate the stone-free rates (SFRs) and stone clearance rates (SCRs) of extracorporeal shock-wave lithotripsy (SWL), retrograde intrarenal surgery (RIRS), and percutaneous nephrolitholapaxy (PCNL) according to non-contrast computer tomography (NCCT) findings. METHODS: Original articles were identified from PubMed. After exclusion of ineligible papers, twenty-three studies with 2494 cases were included in the review. RESULTS: Six SWL, five RIRS and eight PCNL studies were selected. Additionally, four comparative articles were identified. SWL presents SFRs ranging 35-61.3 % and SCRs for residuals <4 mm being 43.2-92.9 %. RIRS studies report SFRs of 34.8-59.7 % and SCRs for residuals <4 mm ranging 48-96.7 %. Finally, PCNL presents SFRs of 20.8-100 % and SCRs for residuals <4 mm being 41.5-91.4 %. According to the comparative studies, SFRs are 17-61.3 % for SWL, 50 % for RIRS, and 95-100 % for PCNL. CONCLUSIONS: According to NCCT findings, it seems that PCNL provides better SFRs than ESWL and RIRS. However, further research with comparable and complete preoperative parameters and outcomes could reduce the heterogeneity of current data.

International Collaboration in Endourology: Multicenter Evaluation of Prestenting for Ureterorenoscopy.

INTRODUCTION: Semirigid and flexible ureterorenoscopy (URS) procedures are safe and efficient treatment options for urolithiasis of all localizations. Sometimes, a Double-J stent is placed in preparation of definitive treatment. The aim of our study was to evaluate the influence of prestenting on the outcome of URS. PATIENTS AND METHODS: We retrospectively analyzed 565 patients of our prospective, multicenter multinational database who underwent URS for renal or ureteral stones from June 2011 to December 2013. Demographic and stone-related data, surgery time, stone clearance, and complications were evaluated. Statistical analysis was performed comparing the prestented and nonstented groups. RESULTS: Demographic data, stone size, and localization were comparable in both groups. Three hundred twenty-three patients were prestented and 242 nonstented. Overall, prestenting had significant influence on the stone-free rate (SFR) (86% prestented vs 74% not prestented, p = 0.0003) and complication rate (6.5% vs 14.5%, p = 0.003), but not on surgery time (55 ± 36 minutes vs 61 ± 35 minutes, p = 0.071). Subgrouped, this was also true for renal stones (83% vs 60%, p = 0.0001, odds ratio [OR] 3.15; confidence interval, CI [1.77, 5.62]/8.7% vs 19.4%, p = 0.02, 0.39 [CI 0.19, 0.83]). For ureteral stones, there was no significant influence on SFR (94% vs 90%, p = 0.4, OR 1.63 [CI 0.63, 4.22]), but significantly more complications (3.1% vs 10.7%, p = 0.02, OR 0.27 [CI 0.08, 0.86]) in the nonstented group. CONCLUSION: Prestenting positively affects safety and efficacy of URS. This is more pronounced in the treatment of kidney stones compared with ureteral stones. Although the SFR for ureteral stones is comparable without prestenting, the complication rate is higher.

Flexible ureterorenoscopy for lower pole stones: influence of the collecting system's anatomy.

BACKGROUND: The impact of renal anatomy on the success rate of flexible ureterorenoscopy (fURS) for lower pole stones is less clear than it is on shock wave lithotripsy, for which it is a recognized influence factor. We analyzed safety and efficiency of fURS using modern endoscopes for lower pole stones dependent on the collecting system's configuration. PATIENTS AND METHODS: We retrospectively evaluated a consecutive sample of 111 fURS for lower pole stones at our tertiary care center between January 2010 and September 2012 from our prospectively kept database. All procedures were performed with modern flexible ureterorenoscopes, nitinol baskets, holmium laser lithotripsy, and ureteral access sheaths whenever needed. The infundibular length (IL) and width (IW) and infundibulopelvic angle (IPA) were measured and the data were stratified for stone-free status and complications classified by the Clavien-Dindo scale. Univariate and multifactorial statistical analyses were performed. Correlation of operation time (OR-time) with anatomical parameters was conducted. RESULTS: Ninety-eight (88.3%) of the 111 patients were stone free after a single fURS. On multifactorial analysis, the stone size and IL had significant influence on the stone-free rate (SFR) (p<0.01), whereas IW did not. An acute IPA (<30°) also had significant influence (p=0.01). The incidence of complications and OR-time were not influenced by the pelvicaliceal anatomy. CONCLUSIONS: fURS is a safe and efficient treatment option for lower pole kidney stones. A long infundibulum and a very acute IPA (<30°) negatively affect the SFR. However, with second look procedures, a complete stone clearance is achievable even in case of unfavorable anatomic conditions. A narrow infundibulum has no negative effect while using modern endoscopes. The complication rate is not affected by the collecting system's anatomy.

Percutaneous nephrolithotomy under combined sonographic/radiologic guided puncture: results of a learning curve using the modified Clavien grading system.

PURPOSE: Aim of our study was to evaluate the results of percutaneous nephrolithotomy (PNL) with sonographic/fluoroscopic guided puncture during a learning curve and to compare them to an expert. METHODS: The first 75 consecutive patients undergoing conventional PNL or Mini-PNL by a novice percutaneous surgeon without direct supervision by an expert were evaluated and divided into three groups of 25 patients each. The results were compared to 50 cases treated by an expert. RESULTS: For mean stone sizes of 22.3 ± 12.9, 22.7 ± 14.9, and 31.1 ± 25.5 mm, the OR-time was 124 ± 35, 106 ± 37, and 99 ± 31 min for the novice groups 1, 2, and 3, respectively. In contrast, the expert required an OR-time of 85 ± 28 min for a mean stone size of 19.7 ± 4.2 mm (p < 0.001; p < 0.01; n.s.). Stone free rates were 100, 96, and 100%; however, second-look procedures were necessary in 24, 16, and 20% of cases, whereas the expert needed only 8% second-look procedures. No complications Clavien IIIb-V occurred. 16, 4, and 8% of patients required a double-J placement (Clavien IIIa) due to hydronephrosis or urine leakage. One patient in the novice group 2 needed transfusion (Clavien II). Other minor complications (Clavien I) occurred in 28, 20 and 12% in the novice groups 1, 2 and 3, respectively, in comparison with 22% in the expert group. CONCLUSIONS: Percutaneous stone treatment under combined sonographic/fluoroscopic guided puncture can be performed safe and efficiently during the learning curve. The lower expertise causes longer operation times and a higher re-intervention rate without compromising the patients' safety.

Flexible ureterorenoscopy versus miniaturized PNL for solitary renal calculi of 10-30 mm size.

INTRODUCTION: The value of flexible ureterorenoscopy (fURS) and miniaturized PNL (mPNL) for larger renal calculi is under discussion. This non-randomized prospective study aimed to evaluate fURS and mPNL for solitary renal stones of 10-30 mm size. MATERIALS AND METHODS: fURS was carried out in 21 patients with last generation 7.5F endoscopes. Ureteral access sheaths were used in 19 patients. For mPNL, an 18F modified Amplatz sheath with a 14F nephroscope were used (n = 25). The procedure was performed either tubeless with an antegrade stent or a nephrostomy. Outcome and complications of both procedures were assessed. RESULTS: Patients' demographics and stone sizes were comparable (18 ± 5 vs. 19 ± 4 mm, P = 0.08). Patients in the fURS group had a higher mean BMI (31 vs. 27, P < 0.05). Total OR time was significantly longer for fURS (106 ± 51 vs. 59 ± 19 min., P < 0.001). More patients were stone-free after one single percutaneous treatment, while 2nd-stage treatments with fURS were common (total procedures 1.04 vs. 1.52, P < 0.001; immediate stone-free rate (SFR) 96% vs. 71.5%, P < 0.001). SFR after 4 weeks was 100% (mPNL) and 85.8% (fURS) (P < 0.01). Minor complications as classified by Clavien I or II occurred in 16 and 23.8%, mPNL and fURS, respectively, P = 0.13). No major complications (Clavien III-V) occured in both groups. CONCLUSIONS: Our series supports both the concept of either percutaneous or retrograde endoscopic treatment for renal calculi with both modalities offering excellent safety. However, while for fURS, a significantly higher rate of 2nd-stage procedures was necessary, and mPNL led to faster and higher SFR without increasing complication rate.