To evaluate the usefulness of the impedance index of the renal vein for the diagnosis of acute obstructive uropathy in rabbits.

Ligation of the left ureter was done in 12 rabbits. Doppler sonography of the interlobar veins in both kidneys was checked before and 30 minutes, 1, 3, 6, 9 and 24 hours after ureteral ligation. The venous impedance index [(peak flow signal-least flow signal)/peak flow signal]was compared between the obstructed and non-obstructed kidneys for all periods. The change in the impedance index after ureteral ligation was also compared between the obstructed and non-obstructed kidneys.

A decrease in the impedance index of the intrarenal vein was observed starting from 30 mins after ureteral ligation, and the index remained low up to 24 hours after ureteral ligation. The obstructed kidneys had a significantly lower impedance index than the contralateral kidneys for all six of the postligation measurements (p< 0.05). There were significant differences in the change of impedance index after ureteral ligation between the obstructed and non-obstructed kidneys (p< 0.05).

The impedance index of the intrarenal vein was significantly decreased in the obstructed kidneys. The measurement of the impedance index of the intrarenal vein using Doppler sonography could provide a useful method of diagnosing obstructive uropathy.