Supine NCCT is not accurate to plan PCNL access in prone position. Prone decubitus is associated with more potential organ injuries in the upper pole. In supine, the kidney situates deeper in the abdomen but the access angle is wider than in prone.

Flexible ureteroscopy is a well-established method for treatment of urinary stones but fl exible ureteroscopes are expensive and fragile devices with a very limited lifetime. Since 2006 with the advent of digital fl exible ureteroscopes a great evolution has occurred. The fi rst single-use fl exible ureteroscope was launched in 2011 and new models are coming to the market. The aim of this article is to review the characteristics of these devices, compare their results with the reusable devices and evaluate the cost-benefi ts of adopting single-use fl exible ureteroscopes in developing countries. Materials and Methods: an extensive review of articles listed at PubMed and published between 2000 and 2021 was performed. Results: Single-use fl exible ureteroscopes have a shaft with 65 to 68cm length and weight between 119 and 277g. Their defl ection goes up to 300 degrees. Their stone-free rates vary between 60 and 95% which is comparable to reusable scopes and operative times ranges from 54 to 86 minutes which are lower when compared to reusable fl exible scopes. Their costs vary between 800 and 3180 US dollars. Conclusion: single-use fl exible ureteroscopes are lighter and have superior quality of image when compared to fi beroptic ones. There are no defi nite data showing a higher stone-free rate or less complications with the use of single-use fl exible ureteroscopes. Each institution must perform a cost-benefi t analysis before making the decision of adopting or not such devices depending on the local circumstances.

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Introduction: We performed a multicentre validation of a nomogram to predict uric acid kidney stones in two populations. Methods: We reviewed the kidney stone database of two institutions, searching for patients with kidney stones who had stone composition analysis and 24-hour urine collection from January 2010 to December 2013. A nomogram to predict uric acid kidneys stones based on patient age, body mass index (BMI), and 24-hour urine collection was tested. Receiver-operating curves (ROC) were performed. Results: We identified 445 patients, 355 from Cleveland, United States, and 90 from Sao Paulo, Brazil. Uric acid stone formers were 7.9% and 8.9%, respectively. Uric acid patients had a significantly higher age and BMI, as well as significant lower urinary calcium than calcium stone formers in both populations. Uric acid had significantly higher total points when scored according to the nomogram. ROC curves showed an area under the curve of 0.8 for Cleveland and 0.92 for Sao Paulo. The cutoff value that provided the highest sensitivity and specificity was 179 points and 192 for Cleveland and Sao Paulo, respectively. Using 180 points as a cutoff provided a sensitivity and specificity of 87.5% and 68% for Cleveland, and 100% and 42% for Sao Paulo. Higher cutoffs were associated with higher specificity. The main limitation of this study is that only patients from high volume hospitals with uric acid or calcium stones were included. Conclusion: Predicting uric acid kidneys stone based on a nomogram, which includes only demographic data and 24-hour urine parameters, is feasible with a high degree of accuracy.

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