Improved ultrasound detection of renal scarring in children following urinary tract infection.

A system for defining renal scarring on ultrasound is proposed and compared with DMSA scintigraphy. Renal scarring was assessed with ultrasound in children following urinary tract infection (UTI) using the following criteria: (1) proximity of sinus echoes to cortical surface; (2) loss of pyramids; (3) irregularity of outline; (4) loss of definition of capsular echo; and (5) calyceal dilatation. Three hundred and thirty-nine consecutive ultrasound scans (US) and DMSA scintigrams, comprising 648 kidneys, were performed and reported blindly and the results were compared. Using DMSA scintigraphy as the gold standard, ultrasound had a positive predictive value of 93% and a negative predictive value of 95%. Ultrasound disagreed with DMSA scintigraphy in 5.2% of kidneys. On review of the cases of disagreement where arbitration was possible by comparison with other imaging, ultrasound was incorrect in 10 kidneys and DMSA was incorrect in 13. We conclude that the sensitivity in the ultrasound detection of renal scarring can be greatly improved using this method. If no scars were detected at ultrasound an alternative explanation for an abnormal DMSA scintigram should be sought.