Renal pyramid echogenicity in ureteropelvic junction obstruction: correlation between altered echogenicity and differential renal function

BACKGROUND: Improvement in resolution and use of high-frequency transducers in US has enabled visualization of previously unreported changes in medullary pyramid echogenicity in children with obstructive hydronephrosis. OBJECTIVE: To determine whether these unreported changes in echogenicity and morphology of the renal pyramids in ureteropelvic junction (UPJ) obstruction correlate with differential renal function (DRF) of the kidney as determined by technetium-99m mercaptoacetyltriglycine ((99m)Tc-MAG3) scan. MATERIALS AND METHODS: Renal sonograms in 60 children with UPJ obstruction were retrospectively reviewed. Children were divided into three groups based on the echogenicity of the pyramids: (1) normal echogenicity of the pyramids, (2) increased echogenicity of the pyramids with maintained corticomedullary differentiation (CMD), and (3) loss of CMD. DRF, as determined by (99m)Tc-MAG3 scan, of the obstructed kidney of >/=45% was considered normal and of