The concept of correlation entails having a couple of observations (X and Y), that is to say, the value that Y acquires for a determined value of X; the correlation makes it possible to examine the trend of two variables to be grouped together. We know that, with increasing age, blood pressure figures also increase, therefore, if we want to answer a research question like “what is the connection between age and blood pressure?” the relevant statistical test is a correlation test. This test makes it possible to quantify the magnitude of the correlation between two variables, but it is also helpful for predicting values. If these variables had a perfect correlation, the value of the variable Y could be deduced by knowing the value of X. Because of these advantages, the correlation is one of the most frequently used tests in the clinical setting since, in addition to measuring the direction and magnitude of the association of two variables, it is one of the foundations for prediction models, such as linear regression model, logistic regression model and Cox proportional hazards model.

Cisplatin, a major antineoplastic drug used in the treatment of solid tumors, is a known nephrotoxin. This retrospective cohort study evaluated the prevalence and severity of cisplatin nephrotoxicity in 54 children and its impact on height and weight. We recorded the weight, height, serum creatinine, and electrolytes in each cisplatin cycle and after 12 months of treatment. Nephrotoxicity was graded as follows: normal renal function (Grade 0); asymptomatic electrolyte disorders, including an increase in serum creatinine, up to 1.5 times baseline value (Grade 1); need for electrolyte supplementation <3 months and/or increase in serum creatinine 1.5 to 1.9 times from baseline (Grade 2); increase in serum creatinine 2 to 2.9 times from baseline or need for electrolyte supplementation for more than 3 months after treatment completion (Grade 3); and increase in serum creatinine ≥3 times from baseline or renal replacement therapy (Grade 4). Nephrotoxicity was observed in 41 subjects (75.9%). Grade 1 nephrotoxicity was observed in 18 patients (33.3%), Grade 2 in 5 patients (9.2%), and Grade 3 in 18 patients (33.3%). None had Grade 4 nephrotoxicity. Nephrotoxicity patients were younger and received higher cisplatin dose, they also had impairment in longitudinal growth manifested as statistically significant worsening on the height Z Score at 12 months after treatment. We used a multiple logistic regression model using the delta of height Z Score (baseline-12 months) as dependent variable in order to adjust for the main confounder variables such as: germ cell tumor, cisplatin total dose, serum magnesium levels at 12 months, gender, and nephrotoxicity grade. Patients with nephrotoxicity Grade 1 where at higher risk of not growing (OR 5.1, 95% CI 1.07–24.3, P = 0.04). The cisplatin total dose had a significant negative relationship with magnesium levels at 12 months (Spearman r = −0.527, P = <0.001).

Objective: To determine the preoperative and perioperative predictive factors of morbidity/mortality in patients undergoing percutaneous nephrolithotomy (PCNL), using the Clavien's classification. Materials and Methods: We performed a retrospective chart review of patients who underwent PCNL between January 2005 and January 2012. Preoperative and postoperative factors, such as age, obesity, surgical risk, Charlson comorbidity index, stone complexity, access calix, type of dilator used, and surgery time, were evaluated as predictors of complications. Results: A total of 354 patients were included in the study. Of these, 56% were women, with the average age of 47±12.5 years. Stone-free rate for noncomplex calculi was 85% and for complex calculi it was 68%. A total of 103 complications were recorded (29.3%). According to the modified Clavien classification system, 32 (9%) were grade 1, 39 (11%) were grade 2, 16 (4.5%) were grade 3A, 8 (2.3%) were grade 3B, 3 (0.8%) were grade 4A, 1 (0.3%) was grade 4B, and 4 (1.1%) were grade 5. In multivariate analysis female gender (odds ratio [OR] 3.1, confidence interval [CI] 1.1–8.0), Charlson score of ≥3 (OR 23.2, CI 3.5–151.1), complex stone (OR 4, CI 1.6–9.6), and duration of surgery of ≥120 minutes (OR 2.9, CI 1.2–6.9) were associated with major complications. Conclusions: PCNL is a safe procedure with acceptable efficacy for the resolution of renal calculi. The safety of the procedure should improve, especially to reduce the presence of severe complications (Clavien ≥3). We identified factors that are associated with severe complications: female gender, high Charlson, complex calculi, and surgical length ≥120 minutes.