The echography of pelvi-ureteric junction obstruction in children.

The echographic appearances seen in 47 children with dilatation of the pelvi-calyceal system but not ureter, in whom the diagnosis of pelvi-ureteric junction obstruction was strong enough to lead to surgical correction, were classed into two categories. Those children in whom the antero-posterior diameter of the pelvi-calyceal system exceeded 10 mm were classed as being 'suspicious' (of pelvi-ureteric junction obstruction). When dilatation of the pelvis was accompanied by dilatation of the calyces this appearance was classed as 'definite'. There was a high false positive rate but a very low false negative rate. A simple water load stress test performed in 17 children helped to decrease the false positives from 16 to 10 but the high false positive rate in the 'definite' group stresses the need for subsequent functional studies. Ultrasound is concluded to be a worthwhile screening test to select children requiring functional studies.