Kidney transplantation: evaluation of donors and recipients

Imaging of the renal transplant: comparison of MRI with duplex sonography

Renal transplantation is an established treatment for patients with end-stage renal disease. Many causes of graft dysfunction are treatable, making prompt detection and diagnosis of complications essential. Sensitive, noninvasive imaging procedures, which do not use iodinated contrast media, are therefore highly desirable to evaluate graft function. Duplex sonography (US) has traditionally been the initial investigation of graft dysfunction. US offers many advantages, particularly during the postoperative period, when it can be performed portably regardless of renal function and can guide percutaneous procedures. However, US lacks specificity in assessing hydronephrosis, cannot differentiate parenchymal causes of dysfunction, and may have difficulty assessing transplant vessels. Recently comprehensive magnetic resonance imaging (MRI) protocols including MR urography, gadolinium-enhanced MR angiography, and MR renography have evolved as a "one-stop" diagnostic technique in the evaluation of the entire graft and peritransplant region. Multiplanar capabilities enable MRI to identify the site of urinary obstruction and assess renal vessels in their entirety. The evolving technique of MR renography may also differentiate parenchymal causes of dysfunction. By combining these three components into a single examination, further information may be obtained regarding the graft when compared with US and other conventional studies, with improved patient convenience, less morbidity, and a potential cost saving.

Assessment of the abdominal aorta and its visceral branches by contrast-enhanced dynamic volumetric hepatic parallel magnetic resonance imaging: feasibility, reliability and accuracy

The purpose of this study was to evaluate a new three-dimensional gradient-echo (GRE) MR sequence performed with a parallel acquisition technique to shorten breath-hold times (parallel GRE MRI) in the detection of arterial variants and stenosis of the abdominal aorta and its visceral branches. A total of 102 patients underwent dynamic parallel GRE MRI, timed to the arterial phase by a test bolus (mean breath-hold time, 17 s). For both quantitative and qualitative analysis, the abdominal aorta and its visceral branches were divided into 13 arterial segments. In a subanalysis of 55/102 patients, the accuracy of parallel GRE MRI compared to MDCT in the detection arterial variants and stenosis was calculated for two independent readers. Mean SNRs and CNRs were 47.2 and 35.6, respectively. Image quality was rated good or excellent in 1,234/1,326 segments (93%). Hepatic and renal arterial variants were identified with an accuracy of 93 and 95%, respectively (reader 1) and 98 and 100%, respectively (reader 2). Both readers detected arterial stenosis with an accuracy of 98%. Interobserver agreement was good to excellent for the detection of hepatic (kappa=0.69) and renal (kappa=0.92) variants and for the diagnosis of stenosis (kappa=0.96). Dynamic three-dimensional parallel GRE MRI is feasible and allows a reliable and accurate diagnosis of arterial variants and stenosis of the abdominal aorta and its visceral branches in a short breath-hold-time.