Renal length discrepancy by ultrasound is a reliable predictor of an abnormal DMSA scan in children

A renal length discrepancy (RLD) of more than 10 mm by ultrasound (US) is accepted as a potential indicator of an underlying renal pathology; however, there are few supporting data for this in children. Our objective was to determine a cutoff at which RLD on US is a reliable predictor of dimercaptosuccinate acid (DMSA) scan abnormality. We present data from 90 patients who had both renal US and a DMSA scan, as well as DMSA scan results compared with bipolar RLD by US. Positive (PPV) and negative (NPV) predictive values were calculated for renal RLD from 6 to > 10 mm. The left kidney was longer in 56%, whereas the right kidney was longer in 37%; their lengths were equal in 8%. For children at all ages, a left kidney longer than the right by >= 10 mm or a right kidney longer than the left by >= 7 mm gave a PPV for DMSA abnormality of 79% and 100%, respectively. In children older than 4 years, if the right kidney was longer by >= 7 mm or if the left kidney was longer by >= 10 mm, the PPVs for DMSA abnormality were 100% and 63%, respectively. In children younger than 4 years, when the right kidney was longer by >= 6 mm or the left was kidney longer by >= 10 mm, the PPV were 86% and 100%, respectively. Thus, children with a right kidney longer than the left by even < 10 mm is a reliable predictor of an abnormal DMSA scan.