One of the most serious problems in the urology is obstructive uropathythat should be solved as soon as possible to prevent rapid deterioration of thekidney function. So, it must be diagnosed early with non invasive, easy to do,inexpensive and reliable tool to distinguish anatomic changes in the upper urinarytract from the true obstruction that affects the renal function. In our study, wetried to evaluate obstructive uropathy and follow up after release of obstructionwith Doppler ultrasound using the resistive index (RI) and delta resistive index(DRI) so that the clinical application of this new tool can be tested as comparedto other gold standard techniques. Between 2005 and 2006, 15 patients withsuggested obstructive uropathy as well as 15 normal individuals were studiedwith Doppler ultrasonography. To get high accuracy a number of exclusion