Detection of renal arteries and classification of haemodynamically relevant renal artery stenoses by colour coded Doppler ultrasound

Aim: Although colour coded Doppler ultrasound (CCDU) is established as a no n-invasive diagnostic tool for detecting renal artery stenoses (RAS), no un iform criterion for defining a hemodynamically relevant stenosis (i.e. angi ographic stenosis of greater than or equal to 70% of the diameter) exists. We therefore investigated the predictive value of the renal-aortic flow-vel ocity ratio (RAR) > 3.5 m/s and a difference of < 0.05 between the left and right side for the resistance index according to Pourcelot (dRI) in the de tection of a relevant RAS. Patients and methods: We analysed 500 consecutiv e CCDU examinations of patients with hypertension retrospectively. An RAR > 3.5 and/or a lateral inequality of the RI < 0.05 were used as stenosis crit erion. Results: In 448 patients (90%) both renal arteries could be found, i n 11 patients (2%) only the right artery, in 6 patients (1%) the left arter y, and in 35 patients (7%) no renal artery was detectable. In 98 patients ( 19.6%), RAS was diagnosed, 69 (71%) of them underwent angiography. 38 patie nts presented an RAR > 3.5 plus dRI > 0.05. In 29 of these, angiography was performed. 96% of them presented with an RAS of greater than or equal to 7 0% and 4% showed an RAS of 40-69% (specificity 97%, sensitivity 76%). In 54 patients the RAR was >3.5, but dRI <0.05. 24% of the patients undergoing a ngiography (n=37) presented with an RAS of <greater than or equal to> 70%, 68% with an RAS of 40 -69%, and 8% with an RAS of <40% (specificity 60%, se nsitivity 100%). 44 hypertensive patients who underwent angiography after a CCDU examination not suggesting the presence of RAS were used as control g roup. Conclusion: An experienced physician using a high quality colour-code d duplex-machine can reliably detect the renal arteries. The presence of RA S can be diagnosed with certainty by CCDU applying the criterion of RAR>3.5 , but the diagnosis of a one-sided haemodynamically relevant RAS can only b e certain if the criterion of dRI > 0.05 is used in addition.