Pediatric MR Urography: Indications, Techniques, and Approach to Review.

Magnetic resonance (MR) urography is a valuable imaging modality for assessing disorders of the pediatric urinary tract. It allows comprehensive evaluation of the kidneys and urinary tract in children by providing both morphologic and functional information without exposing the child to ionizing radiation. Pediatric MR urography can be used to thoroughly evaluate renal and urinary tract abnormalities that are difficult to identify or fully characterize with other imaging techniques, and it has the potential to allow earlier diagnosis while decreasing the number of imaging studies performed. Common indications for pediatric MR urography include evaluation of complex renal and urinary tract anatomy, suspected urinary tract obstruction, operative planning, and postoperative assessment. MR hydrography (T2-weighted imaging of urine) excellently depicts dilated or obstructed urinary systems, whereas postcontrast imaging (gadolinium-enhanced T1-weighted imaging of the kidneys and urinary system) excellently depicts nondilated or nonobstructed urinary systems. Postcontrast MR urography also allows a functional evaluation of the kidneys and urinary tract that includes estimation of differential renal function. The authors review common indications for pediatric MR urography, detail MR urography techniques, compare the strengths and weaknesses of MR urography with those of alternative imaging strategies for children, and describe numerous common and uncommon abnormalities of the pediatric kidneys and urinary tract.