A comparative study between two ultrasound classifications for postnatal urinary tract dilatation

The objective was to test whether the Society for Foetal Urology (SFU) and urinary tract dilatation (UTD) ultrasound classifications for postnatal urinary tract dilatation were able to predict the need for surgical treatment or spontaneous resolution of dilatation.

Retrospective observational study, involving cases whose first ultrasound scans for congenital hydronephrosis were performed between 2008 and 2011. Clinical variables were recorded and each case was classified according to the SFU and UTD classifications. Univariate analysis and binary logistic regression were performed to establish which clinical and ultrasound variables were related to the need for surgery or medical/non-surgical resolution of dilatation.

Data was collected on 231 kidneys. Spontaneous resolution of dilatation occurred in 41.5% of cases and 40.2% required surgery at some point. Age (odds ratio (OR) 1.03) and high degrees of dilatation (P2-P3) in the UTD classification (OR 2.33) were associated with an increased risk of needing surgery, while age (OR 0.95) and high degrees of dilatation (P2-P3) in both the UTD and SFU (3-4) classifications were associated with a lower likelihood of spontaneous resolution (OR 0.23 and 0.27 respectively).

Both the UTD and SFU classifications are good predictors of spontaneous resolution of postnatal urinary tract dilatation, while only the UTD classification is predictive of the need for surgery. Older age at the time of the first ultrasound is associated with a higher risk of needing surgery and a lower likelihood of spontaneous resolution of hydronephrosis.