Multiparametric MR Urography: State of the Art.

Abstract

MR urography (MRU) is an imaging technique that provides comprehensive evaluation of the kidneys, pelvicalyceal system, ureters, and urinary bladder. Although CT urography (CTU) remains the first-line imaging modality for the urinary tract, incremental improvements in MRU have allowed simultaneous imaging of the kidneys, collecting system, and urinary bladder with superior contrast resolution and tissue characterization, equivalent visualization of the upper tracts, and similar specificity for detection of noncalculous diseases of the collecting system compared with that of CTU. MRU has evolved into an alternative to CTU in the broader patient population and a first-line examination in specific patient populations for which CTU is less preferred. This subgroup includes pediatric patients, pregnant patients, patients needing recurring studies, and patients with poor renal function or severe allergies to iodinated contrast material. The most common techniques encompassing a conventional MRU examination include static-fluid T2-weighted imaging and gadolinium-enhanced urothelial and excretory phase imaging. The addition of dynamic contrast-enhanced MRI and diffusion-weighted imaging results in multiparametric MRU that increases diagnostic accuracy. Newer techniques, such as parallel imaging, compressed sensing, radial k-space sampling, and deep learning-based image reconstruction, can shorten examination times and improve image quality and patient compliance. Successful MRU interpretation relies on technique optimization, knowledge of various urinary tract pathologic conditions, and familiarity with different sequences, potential interpretive pitfalls, and artifacts. ^©RSNA, 2025 Supplemental material is available for this article.