MR of the Urogenital Tract in Children

MR urography comprehensively evaluates the urinary tract in a single examination that does not use ionizing radiation (Grattan-Smith and Jones 2008; MD et al. 2010; Vivier et al. 2010b; Jones et al. 2011; Zhang et al. 2013b; Boss et al. 2014; Claudon et al. 2014). MR urography utilizes both static and dynamic imaging, taking advantage of the intrinsically high spatial and contrast resolution to provide high-resolution anatomic images. Additionally, dynamic imaging after administration of intravenous contrast medium is used to obtain functional information about the enhancement, concentration, and excretion of the kidneys using both qualitative and quantitative analysis. The signal changes related to perfusion, concentration, and excretion of the contrast agent can be evaluated sequentially as the contrast agent passes through the renal cortex, the medulla, and then into the collecting systems. Urinary tract anatomy is assessed using a combination of both T2-weighted and contrast-enhanced images. MR urography is similar to intravenous urography but has greater intrinsic contrast, spatial, and temporal resolution. The functional information obtained is comparable to renal scintigraphy but with the important distinction that anatomic images allow the signal originating from the renal parenchyma to be separated from those originating in the collecting system. As a result, the analysis of signal intensity versus time changes in the renal parenchyma can be isolated from those occurring in the collecting system.