Functional, dynamic, and anatomic MR urography: Feasibility and preliminary findings

Rationale and Objectives. The authors assessed the feasibility of using mag netic resonance (MR) urography to acquire functional, dynamic, and anatomic information in human subjects with normal and hydronephrotic kidneys. Materials and Methods. In subjects known to have or suspected of having hyd ronephrosis, split renal filtration fractions were measured with a customiz ed magnetization-prepared, inversion-prepared gradient-recalled echo sequen ce to determine the Tt of flowing blood in the inferior vena cava and aorta before and after contrast medium administration and in the renal veins and arteries after contrast medium administration. Multiple timed sets of coro nal fast spoiled gradient-echo 70 degrees flip-angle images were acquired b efore and after contrast medium administration to derive MR renograms from changes in the signal intensity of the cortex and medulla. Precontrast T2-w eighted images were obtained with a three-dimensional fast spoiled gradient -echo maximum intensity projection pulse sequence, and postcontrast T1 maxi mum intensity projection images were also obtained to depict the renal anat omy. Results. Split filtration fraction differentiated normal from hydronephroti c kidneys, MR renograms depicted vascular, tubular, and ductal phases and d ifferentiated between normal and hydronephrotic kidneys (P < .05, n = 20). Contrast medium dose correlated with the peak of the cortical signal intens ity curves on the renogram (r = 0.7, P < .0005; n = 20). The sensitivities for the visual determination of hydronephrosis and unilateral delayed excre tion of contrast material were both 100%, and the specificities were 64% an d 85%, respectively. Conclusion. The preliminary findings show promise for the use of MR urograp hy in the comprehensive assessment of renal function, dynamics, and anatomy .