Purpose: We used quantitative parameters of renal sonography to differentia
te children with significant obstruction requiring surgical intervention fr
om those without significant obstruction who were followed conservatively.
Materials and Methods: We retrospectively reviewed the records of children
who underwent evaluation for hydronephrosis. Those with a history of vesico
ureteral reflux, anatomical abnormalities or neurogenic bladder were exclud
ed from study. Patients were divided according to hydronephrosis grade into
groups 1-grades III and IV followed conservatively, 2-grades III and IV re
quiring surgical intervention, 3-unilateral grade II and 4-bilateral. All i
mages were scanned into a computer. Renal parenchymal and pelvic area was d
etermined using National Institutes of Health image software. Parenchymal-t
o-pelvic area ratios were calculated from all images. We evaluated the abil
ity of these measurements to determine the likelihood of surgical intervent
ion.
Results: The records of 81 children were available for analysis. Deteriorat
ion in parenchymal area growth was a predictor of surgical intervention. Su
ch patients had catch-up growth of the affected kidney after pyeloplasty. A
parenchymal-to-pelvic area ratio of greater than 1.6 on the initial ultras
ound study after birth predicted cases that would need pyeloplasty in the f
uture (p <0.05). No patient with grade II hydronephrosis required surgical
intervention.
Conclusions: Following serial parenchymal area on serial ultrasound is usef
ul for evaluating children with hydronephrosis. Those with a parenchymal ar
ea below the nomogram for growth usually require pyeloplasty. A parenchymal
-to-pelvic area ratio of less than 1.6 on the initial ultrasound study afte
r birth in patients with prenatally diagnosed ureteropelvic junction obstru
ction or on initial ultrasound in those diagnosed postnatally indicated the
need for surgical intervention in this limited series.