Mapping intravascular extension of Wilms' tumor with magnetic resonance imaging.

Accurate preoperative diagnosis of renal vein, vena caval, or intracardiac extension of Wilms' tumor allows the surgeon to better plan operative vascular control and assess the potential benefits of preoperative chemotherapy. Magnetic resonance imaging (MRI), computed tomography (CT), and ultrasound were used to study four consecutive patients presenting with Wilms' tumor. Three had vena caval involvement, with one of these having a massive right atrial tumor thrombus. A fourth patient had renal vein involvement only. We found MRI to be superior to both CT and ultrasound for mapping intravascular extension of Wilms' tumor and for delineating nonvascular disease. Because of its noninvasiveness, multiplane imaging capabilities, and image contrast and resolution, MRI is a valuable complimentary imaging modality for the diagnosis and follow-up of patients with Wilms' tumor.