Using 3D gadolinium-enhanced MRA for the detection of transplant RAS, Ismaeel et al [46] showed a sensitivity of 93.7%, a specificity of 80%, and an accuracy of 88.5%. In addition, outer cortical necrosis, cortical necrosis with large patches, diffuse cortical necrosis, and both cortical and medullary necrosis were visualized [47]. The loss of corticomedullary differentiation has been described in post-transplant patients with cyclosporine toxicity, rejection, and ATN [12,48,49]. Noncontrast MRA (NC-MRA) with steady-state free precession imaging can help avoid contrast utilization and avoid the risk of NSF [50]. Several studies have evaluated the value of NC-MRA in the evaluation of native RAS [51-57]. In these studies, NC-MRA of renal arteries demonstrated a sensitivity of 78% to 100%, a specificity of 82% to 99%, and an NPV of 95% to 100% in the detection of significant arterial stenosis (>50%). The PPV (57% to 92%) was lower than other parameters. The high NPV suggests that NC-MRA can be used as a screening tool for detecting RAS. When positive, other imaging modalities can be utilized for confirmation and to better assess the degree of stenosis [51]. Although technically more challenging and requiring a longer examination time, 2 small studies suggested that NC-MRA was capable of detecting transplant RAS with a similar accuracy to gadolinium-enhanced MRA [50,58]. Radiography Intravenous Urography and Pyelography Radiography intravenous urography and pyelography are no longer used for evaluation of the renal transplant. Nuclear Medicine Radionuclide tests are valuable in renal transplantation since they provide a noninvasive means to evaluate transplant function qualitatively and also screen for surgical complications. Only scintigraphic studies are able to separate function of the graft from residual function of the native kidneys or any remaining prior failed graft [3]. Renal scintigraphy assesses the 3 sequential phases of renal function.
Renal Transplant Dysfunction. Using 3D gadolinium-enhanced MRA for the detection of transplant RAS, Ismaeel et al [46] showed a sensitivity of 93.7%, a specificity of 80%, and an accuracy of 88.5%. In addition, outer cortical necrosis, cortical necrosis with large patches, diffuse cortical necrosis, and both cortical and medullary necrosis were visualized [47]. The loss of corticomedullary differentiation has been described in post-transplant patients with cyclosporine toxicity, rejection, and ATN [12,48,49]. Noncontrast MRA (NC-MRA) with steady-state free precession imaging can help avoid contrast utilization and avoid the risk of NSF [50]. Several studies have evaluated the value of NC-MRA in the evaluation of native RAS [51-57]. In these studies, NC-MRA of renal arteries demonstrated a sensitivity of 78% to 100%, a specificity of 82% to 99%, and an NPV of 95% to 100% in the detection of significant arterial stenosis (>50%). The PPV (57% to 92%) was lower than other parameters. The high NPV suggests that NC-MRA can be used as a screening tool for detecting RAS. When positive, other imaging modalities can be utilized for confirmation and to better assess the degree of stenosis [51]. Although technically more challenging and requiring a longer examination time, 2 small studies suggested that NC-MRA was capable of detecting transplant RAS with a similar accuracy to gadolinium-enhanced MRA [50,58]. Radiography Intravenous Urography and Pyelography Radiography intravenous urography and pyelography are no longer used for evaluation of the renal transplant. Nuclear Medicine Radionuclide tests are valuable in renal transplantation since they provide a noninvasive means to evaluate transplant function qualitatively and also screen for surgical complications. Only scintigraphic studies are able to separate function of the graft from residual function of the native kidneys or any remaining prior failed graft [3]. Renal scintigraphy assesses the 3 sequential phases of renal function.