Paediatric Doppler—kidney

Abstract

Renal Doppler imaging has been successfully performed, as the blood flow in a normal kidney is important, resulting in a high Doppler signal level. Several Doppler techniques can be used, including color, amplitude, and duplex modes. A precise knowledge of their respective benefits and limitations allows for the appropriate choice, a better optimisation of technical settings in a given patient, and a good understanding of normal vascular anatomy and hemodynamics. From a practical point of view, the wish of a good sensitivity to low blood flow is often compromised by motion artifacts. Other modalities, such as Dynaflow and non-Doppler techniques, have been recently introduced, leading to a better spatial resolution. The actual trend to use higher transmission frequencies further improves the spatial resolution, and increases the sensitivity to flow. New softwares have been introduced, in the attempt to reduce motion artifacts. Clinical applications of Doppler include 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, and the follow-up of patients after renal transplantation. Ureteral jets may be an adjunct for the diagnosis of obstruction of the upper urinary tract in some cases. Doppler has been used for the detection of vesico-ureteral reflux, but now contrast-enhanced US appears more sensitive and reliable.