[Stone free rate assesment after percutaneous nephrolithotomy using nephrolitometric nomogram].

BACKGROUND Percutaneous nephrolithotomy remains the standard of care for kidney stones larger than 2cm. Therefore, setting a prognosis for complete stone resolution through this method is essential. The prognostic tools available have limited prediction. OBJECTIVES To evaluate the stone-free rate in patients undergoing percutaneous nephrolithotomy with the Clinical Research Office of the Endourological Society nomogram and suggest modifications to improve the classification. MATERIAL AND METHODS We analyzed a retrospective cohort of patients undergoing percutaneous nephrolithotomy applying the nephrolithometric nomogram specified. We modified the scale dividing the patients into 3groups: i from 80 to 110 points, II from 111 to 170 points, and III more than 170 points, respectively assessing the stone-free rate (Kruskall-Wallis test was performed, p<0.05). RESULTS A total of 126 patients were included. According to the nehrolithometric nomogram the stone-free rate was 12.5% for patients with fewer than 111 points and 70.9% for those with 111 points or more. In the modification proposed for groups I, IIand III the stone-free rate was 12.5%, 50% and 80% respectively (p=0.000). CONCLUSIONS Evaluation using the nephrolithometric nomogram demonstrated accurate stone-free rate prediction for complex and simple stones, with a lack of discrimination for patients with intermediate scores. Our modification enabled better differentiation of the intermediate groups from the high and low stone-free rate groups.