Common indications for MR urography (MRU) include, but are not limited to,
investigation of the cause of urinary obstruction, evaluation of
urothelial neoplasms, and characterization of complex congenital
anomalies of the urinary system.
When performed properly, MR urography (MRU) can be an alternative to
CT urography (CTU) for imaging of the entire urinary tract. Some
radiologists may prefer MRU for pediatric populations, patients
undergoing repeat examinations, and individuals with compromised renal
‘Meticulous attention to detail is required to optimize the imaging quality of MR urography (MRU). Therefore, researchers have outlined the pitfalls along with potential methods of correcting, detecting or avoiding them.’
However, MRU can be a challenging examination to perform and
interpret; therefore, a team of researchers published a study outlining
the pitfalls along with potential methods of correcting, detecting, or
avoiding them. The information is discussed in the study, "MRI Evaluation of the Urothelial Tract: Pitfalls and Solutions," published in the December 2016 issue of the American Journal of Roentgenology
(AJR). It is available through open accessible on the AJR website.
"Meticulous attention to detail is required to optimize the imaging
quality of MRU, and in our experience, this can be more problematic to
achieve with MRU than with CTU," said study coauthor Nicola Schieda, a
radiologist with the Department of Medical Imaging, The Ottawa Hospital,
"When using the MRU examination, steps must be taken to ensure
adequate distention of the collecting system and dilution of excreted
gadolinium. It is important to recognize normal physiologic
characteristics and expected findings on various pulse sequences,
especially to avoid misinterpretation of strictures related to urinary
peristalsis, filling defects related to flow-related artifacts,
gadolinium mimicking urothelial hemorrhage, or hemorrhage mimicking
tumor. Adequate visualization and evaluation of the entire urinary tract
is critical because urothelial carcinoma frequently presents with
synchronous or metachronous lesions."
A potential advantage of using MRU rather than CTU is related to the
role of MRI in quantitative tumor characterization, the study said. In
particular, apparent diffusion coefficient values obtained from diffused
weighted imaging may help prospectively predict tumor invasive or
proliferative potential, which may affect management decisions.
The study was based on the authors' experience with MR Urography and an extensive review of the literature on the topic.