The role of MR imaging for the assessment of complicated duplex kidneys in children: preliminary report

Objective. To determine whether MR imaging, including MR urography, is able to assess complicated duplex kidneys and to determine the possible role of MRI compared to other imaging techniques in such uropathies. Material and methods. Twenty consecutive patients (age 1 month-11 years) presenting with a suspicion of a complicated duplex kidney were prospectively studied with MRI and MR urography. The examinations were performed on a 0.5-T machine using routinely available sequences that were optimised to the patient's age and size. MR images were reviewed separately by two observers blinded to the patient history. They were asked to assess the presence of a duplex kidney, the presence of an abnormality that may require surgery and to indicate the type of the inferior ureteric insertion. A qualitative gradation of these results was performed on the basis of the final diagnosis provided at endoscopy (n = 6) or surgery (n = 14). MR results were compared to those provided by US examinations and excretory urography, when available, and a non-parametric statistical analysis was performed. Results. MRI differentiated well between the upper and the lower poles of the kidneys and correctly answered the three questions in all 20 patients. The two observers agreed completely in all the 20 patients. MR was statistically superior to both US and excretory urography in the evaluation of the distal ureter (P < 0.05). Conclusions. MRI provides a precise assessment of the complications associated with duplex kidneys. Its optimal role seems to be the assessment of ectopic extra-vesical ureteric insertions and whenever an occult upper pole is suspected.