Antenatal hydronephrosis and postnatal evaluation: Viva

Branch 1: Grading and risk stratification

The candidate should define the antenatal hydronephrosis as the dilatation of the fetal renal collecting system detected on the antenatal ultrasound. A strong candidate describes the two grading systems. The Society for Fetal Urology system, introduced by Fernbach in 1993, grades from 0 to 4 on the basis of the pelvic and the calyceal dilatation and the parenchymal preservation, with the grade 4 defined by the thinning of the renal parenchyma. The Urinary Tract Dilation classification, introduced by Nguyen in the 2014 multidisciplinary consensus, uses the quantitative anteroposterior renal pelvic diameter with the 28-week gestational cutoff and stratifies into the low-risk UTD A1 and the increased-risk UTD A2 to A3. ^[1]

If the examiner presses on the classification of the stimulus case, the candidate should note that the diameter of 9 mm at 32 weeks, with the normal parenchyma and the normal amniotic fluid, falls within the UTD A1 low-risk range of 7 to under 10 mm at 28 weeks or more, provided there are no additional features. The candidate should state that the presence of any additional feature, such as the calyceal dilatation or the ureteric dilatation or the abnormal parenchyma, would upgrade the case to the increased-risk category regardless of the diameter. ^[1]