Renal transplant evaluation with MR angiography and MR imaging

Magnetic resonance (MR) angiography is a widely used, noninvasive tool for evaluating the aorta and its branches. It is particularly useful in renal t ransplant recipients because it provides anatomic detail of the transplant artery without nephrotoxic effects. Volume rendering is underutilized in MR angiography, but this technique affords high-quality three-dimensional MR angiograms, especially in cases of tortuous or complex vascular anatomy. An imaging protocol was developed that includes gadolinium-enhanced MR angiog raphy of the transplant renal artery with volume rendering and multiplanar reformation postprocessing techniques. Axial T2-weighted and contrast mater ial-enhanced T1-weighted MR images are also obtained to examine the renal p arenchyma itself and to evaluate for hydronephrosis or peritransplant fluid collections. This imaging protocol allows rapid global assessment of the r enal transplant arterial system, renal parenchyma, and peritransplant regio n. It can also help detect or exclude many of the various causes of renal t ransplant dysfunction (eg, stenosis or occlusion of a transplant vessel, pe ritransplant fluid collections, ureteral obstruction). Conventional angiogr aphy can thus be avoided in patients with normal findings and reserved for those with MR angiographic evidence of stenosis.