Increased echogenicity as a predictor of poor renal function in children with grade 3 to 4 hydronephrosis

Purpose: Prenatally diagnosed hydronephrosis is a common finding that often requires further radiological evaluation to determine whether it is associated with compromised renal function. We hypothesize that findings on postnatal renal sonography may help determine which patients require more extensive evaluation of renal function in the assessment for prenatal hydronephrosis. We show that increased renal parenchymal echogenicity on postnatal US is a strong predictor of compromised renal function. Materials and Methods: A total of 97 patients diagnosed with prenatal hydronephrosis presented to our institution for farosemide (99m)technetium MAG3 renogram evaluation of renal function between January 2000 and December 2001. All patients had SFU grade 3 to 4 hydronephrosis noted on postnatal US before age 6 months. For these 97 patients (178 renal units) we correlated the degree of renal parenchymal echogenicity and parenchymal thinning on the first postnatal sonogram. with the differential renal function as determined by furosemide MAG3 renography. Results: Among 97 patients diagnosed with prenatal hydronephrosis 10 of 20 renal units (50%) with markedly increased echogenicity had severely decreased relative renal function of less than 10%, while 136 of 151 (90%) with normal echogenicity exhibited normal relative renal function of 40% or greater. Increased echogenicity on US yielded a sensitivity of 100% and specificity of 99% for predicting relative renal function of 20% or greater. In predicting relative renal function of 40% or less sensitivity and specificity were 48% and 100%, respectively. Conclusions: Increased renal parenchymal echogenicity found on the first postnatal ultrasound can be used as a predictor of impaired relative renal function as measured on furosemide MAG3 renogram.