EVALUATION OF DOPPLER ULTRASONOGRAPHY AND DYNAMIC CONTRAST-ENHANCED CT IN ACUTE AND CHRONIC RENAL OBSTRUCTION

The development of a reliable, minimally invasive method of distinguis hing physiologically significant renal obstruction from dilation witho ut obstruction would have important clinical implications, As it is we b known that renal blood flow decreases over time in the presence of o bstruction, we investigated the ability of color flow Doppler ultrason ography and dynamic contrast-enhanced CT scanning to detect changes in blood flow in unilaterally obstructed porcine kidneys, In the initial phase of this study, the effects of acute unilateral obstruction were studied in nine pigs, The resistive index (RI) was measured with Dopp ler ultrasonography, and renal blood flow was quantitated with dynamic CT using tracer kinetic principles and deconvolution. The RI measurem ents were unable to distinguish between the obstructed kidneys and the ir controls, Dynamic CT scanning demonstrated a greater fall in blood flow in the obstructed kidney, and this change was significantly diffe rent from baseline, The same findings were supported by radiolabelled microsphere blood-flow measurement, In the chronic portion of the stud y, after surgical creation of a partial ureteric obstruction, the kidn eys were studied by both techniques at 1, 2, and 3 weeks, Again, RI wa s unable to demonstrate any difference between obstructed and unobstru cted kidneys, while CT showed a progressive fall in blood flow in each successive week that was statistically significant, Dynamic contrast- enhanced CT scanning is a promising diagnostic tool that might be used to distinguish a functionally significant renal obstruction from nono bstructive dilation, Further clinical studies to validate this techniq ue are warranted.