[Changes in kidney stones type according to sex and age in Tunisian patients]

Mediators of the Effects of Gender on Uric Acid Nephrolithiasis: A Novel Application of Structural Equation Modeling

Numerous epidemiological studies have shown that male patients with uric acid nephrolithiasis outnumber female patients. To our knowledge, no research exists evaluating the reasons gender affects the development of uric acid nephrolithiasis. We hereby used a novel application of structural equation modeling to analyze the mediators of the effects of gender on uric acid nephrolithiasis. In 1,098 patients with nephrolithiasis between 2012 and 2016, male gender was found to have a statistically significant positive indirect effect on the development of uric acid nephrolithiasis, which was mediated by lower urine pH (estimate: 0.010, standard error: 0.005, critical ratio: 2.135, 95% confidence interval: 0.002–0.023, P = 0.017), lower estimated glomerular filtration rate (estimate: 0.014, standard error: 0.005, critical ratio: 2.993, 95% confidence interval: 0.006–0.025, P < 0.001), and higher incidence rate of gout (estimate: 0.009, standard error: 0.005, critical ratio: 2.028, 95% confidence interval: 0.002–0.021, P = 0.009). We conclude that low urine pH, impaired renal function, and gout are the mediators of the effect of male gender on the development of uric acid nephrolithiasis. The survey, treatment, and follow-up of kidney diseases, acidic urine, and uric acid metabolism disorders should be considered in men with uric acid nephrolithiasis.

Are there any predictors of pyonephrosis in patients with renal calculus disease?

The objective of the study is to identify factors predicting development of pyonephrosis in patients of renal calculus disease (RCD), as this knowledge is largely unknown. Patients of RCD without pyonephrosis (Group 1) or with pyonephrosis (Group 2) presenting between December 2013 and November 2015 were evaluated. All patients of RCD who had undergone either percutaneous nephrostomy (PCN) or surgical management (percutaneous nephrolithotomy/pyelolithotomy/nephrectomy) were included. Patients treated conservatively, by extracorporeal shock-wave lithotripsy and patients of bilateral RCD were excluded. Data regarding demography, co-morbidities, associated urologic disease, previous intervention, clinical presentation, urinary culture, renal function, grade of hydronephrosis, stone characteristics were collected. 501 patients were included (Group 1: 410; Group 2: 91). Mean age in years (35.02 versus 35.48), sex ratio (2.12:1 versus 2.25:1) and mean body mass index (kg/m²) (22.27 versus 22.15) were similar in both groups. Prevalence of diabetes mellitus (3.41% versus 3.29%, p = 1.000) was similar. Group 2 patients had longer duration of symptoms (5.77 versus 8.96 months, p < 0.0001), associated urological diseases such as ipsilateral PUJO and ureteric calculus (4.63% versus 12.08%, p = 0.0125), moderate/severe-grade hydronephrosis (49.75% versus 92.30%, p < 0.0001), presence of staghorn calculus (20.73% versus 62.63%, p < 0.0001), multiple calculi (48.29% versus 68.13% p = 0.0007) and nonfunctioning kidney (1.70% versus 71.42%, p < 0.0001) as predictors of pyonephrosis. In logistic multivariate analysis, additionally, past history of urological surgery (p = 0.044) was found associated with pyonephrosis. Our study identified some conditions associated with patients of pyonephrosis. To prove their role as risk factors we recommend further studies.