Fetal kidney charts of a novel measurement of the renal parenchymal thickness to evaluate fetal kidney growth and potential function.

OBJECTIVE: The objective of this study was to develop new standard growth charts for fetal renal parenchymal thickness, length, and volume to define normal ranges for use in clinical practice and to assess the reliability of these measurements. METHODS: This was a prospective, longitudinal study of 72 low-risk singleton pregnancies undergoing serial ultrasound examinations at least every four weeks. Multiple renal measurements were performed on both kidneys at each scan. The renal parenchymal thickness was measured in the mid-sagittal plane. Standard charts were developed and the intra and interobserver reliability for the renal measurements was analysed. RESULTS: Standard charts were developed for fetal renal parenchymal thickness, length, and volume. CONCLUSION: We present novel charts, which demonstrate the growth of the fetal renal parenchyma during pregnancy. They will be useful in clinical practice to identify any alterations from these normal ranges, which may be an important criterion for assisting prenatal diagnosis of renal pathologies and future studies in the prediction of kidney function.

Prenatal renal parenchymal area as a predictor of early end-stage renal disease in children with vesicoamniotic shunting for lower urinary tract obstruction.

BACKGROUND: Vesicoamniotic shunting (VAS) and other bladder drainage techniques for fetal lower urinary tract obstruction (LUTO) have been proven to ameliorate pulmonary hypoplasia and increase survival in patients with an initial poor prognosis. Currently there are limited prognostic tools available during gestation to evaluate and predict postnatal renal function. OBJECTIVE: The aim was to describe the prenatal growth of the renal parenchymal area (RPA) in patients with LUTO and determine its application as a predictor of renal function at one year of life. STUDY DESIGN: The study population comprised a retrospective cohort of all infants who survived the fetal VAS to birth. Renal growth and size were measured using imageJ software to calculate the RPA in sequential prenatal ultrasounds. The parenchymal area was measured from the image of each kidney with the greatest longitudinal length. These measurements were further correlated and analyzed as a predictor of end-stage renal disease (ESRD) within the first year of life. RESULTS: Etiologies of LUTO in the 15 male fetuses included eight posterior urethral valves, four Eagle-Barrett/prune belly syndrome, two urethral atresia, and one megacystis microcolon intestinal hypoperistalsis syndrome. All patients had patent shunts, in place, at birth. Furthermore, ultrasonographic parameters such as oligohydramnios, keyhole sign, and bladder wall thickness showed no statistical difference between groups. Renal parenchymal growth correlated with postnatal renal function in both the ESRD (r = 0.409, p = 0.018) and the non-ESRD (r = 0.657, p < 0.001) groups. Most notably, RPA during the 3rd trimester predicted ESRD with the best cut-off point determined to be 8 cm2 (sensitivity, 0.714; specificity, 0.882; and positive likelihood ratio, 6.071) (Table). DISCUSSION: Despite definitive VAS for LUTO, postnatal morbidity and mortality remain high, emphasizing the role of renal dysplasia in postnatal renal failure, in spite of urinary diversion. Renal growth statistically differs between groups in the 3rd trimester of gestation; RPA development appears stagnant in patients that developed ESRD within the first year of life. In contrast, patients that did not develop ESRD continued to have renal parenchymal growth in a linear fashion. This suggests that prenatal RPA may be predictive of postnatal ESRD. CONCLUSIONS: RPA measurement during the prenatal period could play an important role as a non-invasive tool to predict postnatal renal function and to anticipate postnatal clinical interventions.