The life cycle of the kidney: implications for CKD

Associations of maternal and foetoplacental factors with prehypertension/hypertension in early childhood

OBJECTIVE

To evaluate whether characterization of maternal and foetoplacental factors beyond birthweight can enable early identification of children at risk of developing prehypertension/hypertension.

METHODS

We recruited 693 mother-offspring dyads from the GUSTO prospective mother-offspring cohort. Prehypertension/hypertension at age 6 years was identified using the simplified paediatric threshold of 110/70 mmHg. We evaluated the associations of pregnancy complications (gestational diabetes, excessive/inadequate gestational weight gain, hypertensive disorders of pregnancy), foetal growth deceleration (decline in foetal abdominal circumference at least 0.67 standard deviations between second and third trimesters), high foetoplacental vascular resistance (third trimester umbilical artery systolic-to-diastolic ratio ≥90th centile), preterm birth, small-for-gestational age and neonatal kidney volumes with risk of prehypertension/hypertension at age 6 years, after adjusting for sex, ethnicity, maternal education and prepregnancy BMI.

RESULTS

Pregnancy complications, small-for-gestational age, preterm birth, and low neonatal kidney volume were not associated with an increased risk of prehypertension/hypertension at age 6 years. In contrast, foetal growth deceleration was associated with a 72% higher risk [risk ratio (RR) = 1.72, 95% confidence interval (CI) 1.18-2.52]. High foetoplacental vascular resistance was associated with a 58% higher risk (RR = 1.58, 95% CI 0.96-2.62). Having both these characteristics, relative to having neither, was associated with over two-fold higher risk (RR = 2.55, 95% CI 1.26-5.16). Over 85% of the foetuses with either of these characteristics were born appropriate or large for gestational age.

CONCLUSION

Foetal growth deceleration and high foetoplacental vascular resistance may be helpful in prioritizing high-risk children for regular blood pressure monitoring and preventive interventions, across the birthweight spectrum.

Quantitative renal magnetic resonance imaging: magnetic resonance urography

The goal of functional renal imaging is to identify and quantitate irreversible renal damage and nephron loss, as well as potentially reversible hemodynamic changes. MR urography has evolved into a comprehensive evaluation of the urinary tract that combines anatomical imaging with functional evaluation in a single test without ionizing radiation. Quantitative functional MR imaging is based on dynamic contrast-enhanced MR acquisitions that provide progressive, visible enhancement of the renal parenchyma and urinary tract. The signal changes related to perfusion, concentration and excretion of the contrast agent can be evaluated using both quantitative and qualitative measures. Functional evaluation with MR has continued to improve as a result of significant technical advances allowing for faster image acquisition as well as the development of new tracer kinetic models of renal function. The most common indications for MR urography in children are the evaluation of congenital anomalies of the kidney and urinary tract including hydronephrosis and renal malformations, and the identification of ectopic ureters in children with incontinence. In this paper, we review the underlying acquisition schemes and techniques used to generate quantitative functional parameters including the differential renal function (DRF), asymmetry index, mean transit time (MTT), signal intensity versus time curves as well as the calculation of individual kidney glomerular filtration rate (GFR). Visual inspection and semi-quantitative assessment using the renal transit time (RTT) and calyceal transit times (CTT) are fundamental to accurate diagnosis and are used as a basis for the interpretation of the quantitative data. The importance of visual assessment of the images cannot be overstated when analyzing the quantitative measures of renal function.

The old becomes new: advances in imaging techniques to assess nephron mass in children

Renal imaging is widely used in the assessment of surrogate markers of nephron mass correlated to renal function. Autopsy studies have tested the validity of various imaging modalities in accurately estimating "true" nephron mass. However, in vivo assessment of nephron mass has been largely limited to kidney volume determination by ultrasonography (US) in pediatric populations. Practical limitations and risks create challenges in incorporating more precise 3D volumetric imaging, like magnetic resonance imaging (MRI), and computed tomography (CT) technologies, compared to US for routine kidney volume assessment in children. Additionally, accounting for structural anomalies such as hydronephrosis when estimating renal parenchymal area in congenital anomalies of the kidney and urinary tract (CAKUT) is important, as it correlates with chronic kidney disease (CKD) progression. 3D imaging using CT and MRI has been shown to be superior to US, which has traditionally relied on 2D measurements to estimate kidney volume using the ellipsoid calculation. Recent innovations using 3D and contrast-enhanced US (CEUS) provide improved accuracy with low risk. Indexing kidney volume to body surface area in children is an important standard that may allow early detection of CKD progression in high-risk populations. This review highlights current understanding of various imaging modalities in assessing nephron mass, discusses applications and limitations, and describes recent advances in the field of imaging and kidney disease. Although renal imaging has been a long-standing, essential tool in assessing kidney disease, innovation and new applications of established technologies provide important tools in the study and management of kidney disease in children.

Signs and symptoms of developmental abnormalities of the genitourinary tract

OBJECTIVE

The abnormalities of the genitourinary tract development are the leading cause of chronic kidney disease (CKD) in children. The diagnosis of this disease in Brazil is late and incomplete, which results in increased morbidity and mortality in this age group. Early diagnosis of this condition is the prerogative of generalist pediatricians, and the aim of this study was to review the clinical signs and symptoms associated with developmental abnormalities of the genitourinary tract.

DATA SOURCES

Based on the description of a symbolic clinical case, the authors conducted a non-systematic review of medical literature.

DATA SYNTHESIS

The results suggest that the following data should be used as a warning for early diagnosis of affected children: (a) combined urinary tract abnormalities (chromosomal abnormalities; sequence of malformations [VACTERLand Prune-Belly]; and musculoskeletal, digestive tract, heart, and nervous system malformations); (b) previous history (congenital anomalies of the kidney and urinary tract [CAKUT] in the family, low birth weight, and oligoamnios); (c) clinical signs (polyuria/nocturia, urinary tract infection, systemic arterial hypertension, failure to thrive, weak urinary stream, difficulty to start urination, distended bladder, non-monosymptomatic enuresis, urinary/urge incontinence, and bowel and bladder dysfunction); and (d) pre- and postnatal ultrasonographic alterations (increased anteroposterior diameter of the renal pelvis, mainly in the third trimester of pregnancy; single kidney; hydronephrosis associated with other abnormalities; and hydronephrosis with parenchymal involvement in the post-neonatal assessment).

CONCLUSION

The suggestions shown here can help the pediatrician to establish clinical hypotheses for the early diagnosis of developmental abnormalities of the genitourinary tract without resorting to expensive and invasive procedures.