MR urography.

Developments of MR imaging of static fluid has led to the emergence of MR urography (MRU) as a potential imaging technique of the urinary system. MRU has been shown to be highly sensitive in the diagnosis of urinary obstruction, defining the severity of dilatation, the site, and in the majority of cases, the cause of obstruction. At the current level of resolution, however, MR cannot consistently demonstrate nonobstructive or small obstructing calculi. Demonstration of perinephric and periuretic edema in obstruction helps in the differentiation of acute from nonacute urinary obstruction. MRU has shown potential in the work-up of urinary disease for which intravenous urography used to be performed, without the hazards of intravenous contrast administration.