Renal Doppler imaging has been successfully performed for years, as the Doppler signal is high as a result of a marked blood flow. Several Doppler techniques can be used, including colour, amplitude and duplex modes. A precise knowledge of their respective benefits and limitations allow for the appropriate choice, a better optimisation of technical settings in a given patient, and understanding of normal vascular anatomy and hemodynamics. The actual trend to use higher transmission frequencies further improves the spatial resolution, and is expected to increase the sensitivity but should be balanced with attenuation. In children, the examination is often difficult because of motion and breath related artefacts, the size of the vessels, the heart rate and hemodynamics.

Clinical applications of Doppler include the diagnosis of renal artery stenosis based on direct and indirect signs, the detection and follow-up of renal vein or artery thrombosis, the diagnosis of acute pyelonephritis, the evaluation of vascularity of renal tumors and pseudotumors, the detection of crossing vessels in UPJ syndromes, the follow-up of patients after renal transplantation. In some specific case, the adjunct of contrast may appear useful to display macro- and micro vasculature defects. Doppler has also been used for the detection of vesico-ureteral reflux, but now contrast-enhanced US appears more sensitive and reliable.