The ureteric jet index: a novel measure of divided renal function

The aim of this study was to evaluate an index of divided renal function based on the quantification of the ureteric jets seen on colour Doppler ultrasound of the bladder. Thirty-one patients attending for scintigraphic renography underwent colour Doppler ultrasound with video recording for 5 min. Divided renal function was calculated as the proportion of jets from the right-sided orifice ('jet index'). This was compared with the corresponding 'scintigraphic index' found using Patlak-Rutland graphical analysis. Absolute discrepancies were calculated. Twenty-eight of thirty-one (90%) of studies were diagnostic for the calculation of jet indices. The mean jet index was 52% (n=28, SEM=5.8%) compared to a mean scintigraphic index of 54% (n = 28, SEM = 4.0%). The two scores were correlated, with a correlation coefficient of 0.72 and the median absolute difference between the two scores was 7.7%. Forty-three per cent (12/28) of subjects had discrepancies in the two scores of 5% or less. The score differences, however, showed a highly skewed distribution with 32% (9/28) subjects showing discrepancies over 20%. This discordant group (> 20% difference) included three patients with functional pelviureteric obstruction, one with a pelvic mass and one with an underfilled bladder. Two patients with very poor quality jets had impaired renal function. In one case, the index improved after angioplasty for renal artery stenosis. This simple test is a useful adjunct to urinary tract ultrasound but should be interpreted alongside evidence of renal obstruction, and complements rather than replaces existing tests.