RESUMO
BACKGROUND AND OBJECITVES: The currently available kidney volume normative values in children are restricted to small populations from single-centre studies not assessing kidney function and including none or only a small number of adolescents. This study aimed to obtain ultrasound-based kidney volume normative values derived from a large European White/Caucasian paediatric population with normal kidney function. METHODS: After recruitment of 1427 children aged 0-19 years, 1396 individuals with no history of kidney disease and normal estimated glomerular filtration rate were selected for the sonographic evaluation of kidney volume. Kidney volume was correlated with age, height, weight, body surface area and body mass index. Kidney volume curves and tables related to anthropometric parameters were generated using the LMS method. Kidney volume predictors were evaluated using multivariate regression analysis with collinearity checks. RESULTS: No clinically significant differences in kidney volume in relation to height were found between males and females, between supine and prone position and between left and right kidneys. Males had, however, larger age-related kidney volumes than females in most age categories. For the prediction of kidney volume, the highest coefficient correlation was observed for body surface area (r = 0.94), followed by weight (r = 0.92), height (r = 0.91), age (r = 0.91), and body mass index (r = 0.67; p < 0.001 for all). CONCLUSIONS: This study presents LMS-percentile curves and tables for kidney volume which can be used as reference values for children aged 0-19 years.
RESUMO
A major maternal adaptation in pregnancy is the large increase in uteroplacental blood flow that supplies the growing fetus with oxygen and nutrients. The impact of gestation on the dynamic uterine vasoconstrictor response to exercise in the rat, a common model for pathophysiological disorders in pregnancy remains unknown. We hypothesized that rats exhibit a robust uterine vasoconstrictor response to acute exercise that is attenuated in late pregnancy. Pregnant (P, N = 12) and nonpregnant (NP, N = 8) rats were instrumented chronically with a ultrasonic transit-time flowprobe and carotid arterial catheter to directly measure uterine artery blood flow (UtBF) and blood pressure (BP), respectively, at day 20 of gestation for 5 min of treadmill exercise (7 m/min; 6% grade). Preexercise UtBF [P, 2.1 (SD1.6) vs. NP, 0.5 (SD0.3) mL/min P < 0.01) and uterine artery conductance (UtC) [P, 2.1(SD1.7) vs. NP, 0.4 (SD0.2) mL/min × mmHg(-1) × 10(-2), P < 0.01] were higher in pregnant rats, whereas preexercise BP was lower in the pregnant rats [P, 111 (SD13) vs. NP, 126 (SD13) mmHg, P = 0.02]. Preexercise heart rate was similar [P, 457 (SD30) vs. NP, 454 (SD42), P = 0.3]. Exercise initiated rapid and sustained decreases in UtBF [Δ-47% (SD12)] and UtC [Δ-49% (SD12)] that were attenuated in the pregnant rats [UtBF, Δ-25% (SD20) and UtC, Δ-30% (SD20), P = 0.02]. The BP and heart rate responses to exercise were unaffected in late pregnancy (interaction term, P = 0.3). In rats, dynamic exercise induces a uterine vasoconstrictor response that is blunted during late gestation, a response that we observed previously in pregnant rabbits.
