Evaluation of sonographic renal parenchymal area in the management of hydronephrosis

Purpose: We used quantitative parameters of renal sonography to differentiate children with significant obstruction requiring surgical intervention from 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 vesicoureteral reflux, anatomical abnormalities or neurogenic bladder were excluded from study. Patients were divided according to hydronephrosis grade into groups 1-grades III and IV followed conservatively, 2-grades III and IV requiring surgical intervention, 3-unilateral grade II and 4-bilateral. All images were scanned into a computer. Renal parenchymal and pelvic area was determined using National Institutes of Health image software. Parenchymal-to-pelvic area ratios were calculated from all images. We evaluated the ability of these measurements to determine the likelihood of surgical intervention. Results: The records of 81 children were available for analysis. Deterioration in parenchymal area growth was a predictor of surgical intervention. Such 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 ultrasound study after birth predicted cases that would need pyeloplasty in the future (p <0.05). No patient with grade II hydronephrosis required surgical intervention. Conclusions: Following serial parenchymal area on serial ultrasound is useful for evaluating children with hydronephrosis. Those with a parenchymal area below the nomogram for growth usually require pyeloplasty. A parenchymal-to-pelvic area ratio of less than 1.6 on the initial ultrasound study after birth in patients with prenatally diagnosed ureteropelvic junction obstruction or on initial ultrasound in those diagnosed postnatally indicated the need for surgical intervention in this limited series.