A nephrolithometric nomogram to predict treatment success of percutaneous nephrolithotomy.

PURPOSE: Imaging is routinely done preoperatively and postoperatively to assess patients treated with percutaneous nephrolithotomy. We developed a nomogram for percutaneous nephrolithotomy success. MATERIALS AND METHODS: From November 2007 to December 2009 the CROES (Clinical Research Office of the Endourological Society) collected data on consecutive patients at 96 centers globally. Patients were evaluated for stone-free status using plain x-ray of the kidneys, ureters and bladder. Treatment success was defined as no visible stones or residual fragments less than 4 mm. Multivariate regression was used to model the relationship between preoperative descriptors and the stone-free rate. Variables included case load, prior treatment, body mass index, staghorn stones, renal anomalies, and stone burden, location and count. Bootstrapping techniques were used to validate the model. Adjusted chi-square statistic values were used to rank the prognostic value of variables. A nomogram was developed using significant predictors from the model. We assessed the predictive accuracy of the nomogram using the ROC curve AUC. The nomogram was calibrated. RESULTS: Stone burden was the best predictor of the stone-free rate (chi-square = 30.27, p <0.001). Other factors associated with the stone-free rate were case volume (chi-square = 35.75, p <0.001), prior stone treatment (chi-square = 14.55, p <0.012), staghorn stone (adjusted chi-square = 4.73, p <0.029), stone location (chi-square = 14.74, p <0.001) and stone count (chi-square = 4.78, p <0.004). A nephrolithometric nomogram was developed with predictive accuracy (AUC 0.76). CONCLUSIONS: The percutaneous nephrolithotomy stone-free rate can be predicted using preclinical data and radiological information. We present a nephrolithometric nomogram for percutaneous nephrolithotomy.

Does imaging modality used for percutaneous renal access make a difference? A matched case analysis.

OBJECTIVE: To assess perioperative outcomes of percutaneous nephrolithotomy (PCNL) using ultrasound or fluoroscopic guidance for percutaneous access. METHODS: A prospectively collected international Clinical Research Office of the Endourological Society (CROES) database containing 5806 patients treated with PCNL was used for the study. Patients were divided into two groups based on the methods of percutaneous access: ultrasound versus fluoroscopy. Patient characteristics, operative data, and postoperative outcomes were compared. RESULTS: Percutaneous access was obtained using ultrasound guidance only in 453 patients (13.7%) and fluoroscopic guidance only in 2853 patients (86.3%). Comparisons were performed on a matched sample with 453 patients in each group. Frequency and pattern of Clavien complications did not differ between groups (p=0.333). However, postoperative hemorrhage and transfusions were significantly higher in the fluoroscopy group: 6.0 v 13.1% (p=0.001) and 3.8 v 11.1% (p=0.001), respectively. The mean access sheath size was significantly greater in the fluoroscopy group (22.6 v 29.5F; p<0.001). Multivariate analysis showed that when compared with an access sheath ≤ 18F, larger access sheaths of 24-26F were associated with 3.04 times increased odds of bleeding and access sheaths of 27-30F were associated with 4.91 times increased odds of bleeding (p<0.05). Multiple renal punctures were associated with a 2.6 odds of bleeding. There were no significant differences in stone-free rates classified by the imaging method used to check treatment success. However, mean hospitalization was significantly longer in the ultrasound group (5.3 v 3.5 days; p<0.001). CONCLUSIONS: On univariate analysis, fluoroscopic-guided percutaneous access was found to be associated with a higher incidence of hemorrhage. However, on multivariate analysis, this was found to be related to a greater access sheath size (≥ 27F) and multiple punctures. Prospective randomized trials are needed to clarify this issue.

Categorisation of complications and validation of the Clavien score for percutaneous nephrolithotomy.

BACKGROUND: Although widely used, the validity and reliability of the Clavien classification of postoperative complications have not been tested in urologic procedures, such as percutaneous nephrolithotomy (PCNL). OBJECTIVE: To validate the Clavien score and categorise complications of PCNL. DESIGN, SETTING, AND PARTICIPANTS: Data for 528 patients with complications after PCNL were used to create a set of 70 unique complication-management combinations. Clinical case summaries for each complication-management combination were compiled in a survey distributed to 98 urologists, who rated each combination using the Clavien classification. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Interrater agreement for Clavien scores was estimated using Fleiss' kappa (κ). The relationship between Clavien score and the duration of postoperative hospital stay was analysed using multivariate nonlinear regression models that adjusted for operating time, preoperative urine microbial culture, presence of staghorn stone, and use of postoperative nephrostomy tube. RESULTS AND LIMITATIONS: Overall interrater agreement in grading postoperative complications was moderate (κ=0.457; p<0.001). Agreement was highest for Clavien score 5 and decreased with lower Clavien scores. Higher agreement was found for Clavien scores 3 and 4 than in subcategories of these scores. Postoperative stay increased with higher Clavien scores and was unaffected by inherent differences between study centres. A standard list of post-PCNL complications and their corresponding Clavien scores was created. CONCLUSIONS: Although the Clavien classification demonstrates high validity, interrater reliability is low for minor complications. To improve the reliability and consistency of reporting adverse outcomes of PCNL, we have assigned Clavien scores to complications of PCNL.