Doppler ultrasonographic indices in diagnosing nutcracker syndrome in children

To elucidate the Doppler ultrasonographic cut-off value of nutcracker syndrome causing hematuria in children, we analyzed Doppler spectral findings between 15 children with nutcracker syndrome and 15 age- and sex-matched normal control subjects. A follow-up Doppler ultrasound (US) was also performed in children with nutcracker syndrome when hematuria subsided completely after a median period of 1.7 years (range: 1.0-3.5 years) (relieved nutcracker syndrome). The peak velocity (PV) ratios of the left renal vein (LRV) were significantly higher in children with nutcracker syndrome than in those with relieved nutcracker syndrome (P<0.0001) and normal children (P<0.0001). The PV ratios of the LRV at the follow-up US were significantly higher than those in the control subjects (P=0.019). None of the 15 normal children showed PV ratios of the LRV>3.7, but five of the 15 children with relieved nutcracker syndrome without hematuria had PV ratios of 3.91-5.02. When we set the cut-off values for nutcracker syndrome at the mean+/-2 SD (mean: 2.95+/-0.92, range: 1.60-5.02) of 30 controls (normal children and relieved nutcracker without hematuria), the calculated cut-off value was 4.8, and the sensitivity and specificity were 100% and 93%, respectively. Given its high sensitivity, renal Doppler US can be used as a useful initial non-invasive test in the diagnosis of nutcracker syndrome in children with hematuria.