Blood pressure and urolithiasis in children.

INTRODUCTION: Urolithiasis is a condition that is most commonly found in adults, but is becoming increasingly prevalent in children. Little is known about the relationship between blood pressure (BP) and urolithiasis in children. OBJECTIVES: The aim was to evaluate the relationship between urolithiasis and BP, and to determine the association of BP with 24-h urine parameters in children. METHODS: We retrospectively analyzed BP and 24-h urine data from children <18 years with and without urolithiasis from 2004 to 2015 at a single tertiary center. Children with a diagnosis of non-glomerular hematuria without history of urolithiasis were chosen as the control group. Non-stone formers were excluded if they presented with any abnormal 24-h urine data or kidney disease. Casual BP, BP index (BPi), and 24-h urine parameters were compared between groups using t-tests. Multiple regression analyses adjusting for age, sex and body mass index (BMI) z-score evaluated the association of BP with urolithiasis and urine electrolytes. RESULTS: The urolithiasis group (N = 71) was significantly older, taller and heavier than the non-stone former group (N = 53) (Table). Systolic BP and diastolic BP in stone formers were significantly greater than in non-stone formers, respectively (p = 0.019). Additionally, systolic BPi was significantly higher in the urolithiasis group (p = 0.03) but there was no significant difference in diastolic BPi (p = 0.45). Urolithiasis was a significant predictor of systolic BPi in the adjusted model (ß = 0.04, 95% CI 0.001-0.07). In stone formers, systolic BP and systolic BPi were directly associated with 24-h urine sodium, oxalate/1.73 m2, and uric acid (all p < 0.05). Urine calcium was not associated with any BP parameter. DISCUSSION: The findings are consistent with previous studies in adults that examined the correlation between blood pressure and kidney stones. The results of this study also showed that blood pressure was positively associated with urine sodium, oxalate, and uric acid. Interestingly, contrary to adult literature, our hypothesis which postulated that blood pressure would be associated with an increase in urine calcium was not supported by our findings. The small sample size is a study limitation and the use of healthy controls as a comparison would have been ideal. CONCLUSIONS: Blood pressure was directly associated with urolithiasis children. Greater BP values were also associated with abnormalities in 24-h urine oxalate, uric acid, and sodium values. Interestingly, BP was not associated with urine calcium in this population.

Kidney volume and ambulatory blood pressure in children.

Low nephron number has been shown to be a risk factor for hypertension (HTN) in adulthood. Kidney volume may serve as a surrogate marker for nephron mass. The relationship between kidney volume and ambulatory blood pressure (BP) in the pediatric population is not known. A retrospective chart review of children younger than 21 years who were evaluated for HTN was performed. Twenty-four-hour BP and ultrasonography data were obtained. Multiple regression was used to examine associations between BP and kidney volume. Of 84 children (mean age 13.87 years, 72.6% males), 54 had HTN. Systolic BP index during the awake, sleep, and 24-hour periods (all P≤.05) was found to be positively correlated with total kidney volume. Greater total kidney volume was found to be a positive predictor of 24-hour and sleep systolic index (P≤.05). It failed to serve as a predictor of HTN, pre-HTN, or white-coat HTN. Contrary to expectation, total kidney volume was positively associated with systolic BP indices.

Role of race in kidney transplant outcomes in children with focal segmental glomerulosclerosis.

It is well established that racial differences exist in kidney transplant outcomes; however, there are no studies which focus on the role of race in transplant outcomes specifically in children diagnosed with FSGS. Associations between race and transplant outcomes in FSGS children were evaluated using the Organ Procurement and Transplantation Network database from 2000 to 2012. Recipients aged 2-21 years who received a kidney-only transplant were included. Multivariate regression models were used to evaluate transplant outcomes by race. Five hundred and thirty-six recipients (59.7% male, 15.6±3.9 years) were black and 1134 (55.7% male, 14.3±5.0 years) were non-black. Graft survival was significantly shorter in the black group (4.2±3.1 vs 4.6±3.3 years, P=.005). Black race was associated with significantly higher risk of graft failure (HR 1.34, 95% CI=1.21-1.49, P<.0001), acute rejection (OR 1.66 95% CI=1.39-1.97, P<.0001), and delayed graft function (OR 1.51, 95% CI=1.33-1.72, P<.001) compared to non-black race. There were no significant differences in mortality, prolonged hospitalization, or FSGS recurrence between groups. Race is a significant predictor for worse transplant outcomes in children with FSGS.

Blood pressure variability in children with primary vs secondary hypertension.

Increased blood pressure variability (BPV) is correlated with adverse cardiovascular (CV) events in adults. However, there has been limited research on its effect in the pediatric population. Additionally, BPV differences between primary and secondary hypertension (HTN) are not known. Children with primary and secondary HTN underwent 24-hour ambulatory blood pressure monitoring and echocardiography studies. BPV measures of standard deviation (SD), average real variability (ARV), and range were calculated for the 24-hour, daytime, and nighttime periods. Seventy-four patients (median age, 13.5 years; 74% boys) were examined, 40 of whom had primary HTN. Body mass index z score and age were independent predictors of systolic ARV (R(2) =0.14) and SD (R(2) =0.39). There were no statistically significant differences in overall or wake period BPV measures between secondary or primary HTN groups, but sleep period diastolic SD was significantly greater in the secondary HTN group (9.26±3.8 vs 7.1±2.8, P=.039). On multiple regression analysis, secondary HTN was associated with increased sleep period diastolic SD (P=.025). No metrics of BPV in the overall, wake, and sleep periods were found to be significantly associated with left ventricular hypertrophy (LVH). The results of this study do not show a strong relationship between overall or wake BPV with primary vs secondary HTN, but the association of secondary HTN with sleep period diastolic BPV deserves further exploration. Contrary to expectation, the findings of this study failed to indicate a relationship between BPV and LVH for all patients as well for primary hypertensive and secondary hypertensive patients.