Renal power Doppler ultrasound does not predict renal scarring after urinary tract infection

Objective: Young children may develop renal scarring following a urinary tract infection (UTI) especially after pyelonephritis which is difficult to diagnose. Permanent renal scars are diagnosed by dimercapto-succinic acid (DMSA) scan several months later. To decrease unnecessary exposure to radiation, we investigate the role of renal power Doppler (RPD) in predicting those who may not require a late DMSA scan. Methods: Children under four years of age with a first UTI underwent an RPD study soon after diagnosis, and a DMSA scintigraphy six months later. The predictive values of the early RPD to detect DMSA renal scarring were calculated. Results: Twenty three children (median age 30 months) were enrolled: 13 had a febrile presentation, two with bacteraemia. Permanent scarring occurred in three children (13%). In the 46 kidney units studied, initial RPD was abnormal in two and late DMSA abnormal in three units. Overall concordance between RPD and DMSA was 93.5%. The sensitivity of RPD for renal scar as per DMSA was 33.3%, specificity 97.7%; positive predictive value 50% and a negative predictive value of 95.4%. Conclusions: RPD offered no advantage over ultrasound to predict renal scarring and cannot be recommended to predict renal scarring following UTI.