Retroperitoneal MR imaging.

Although CT is usually the first imaging study used to evaluate for retroperitoneal disease, MR imaging is increasingly chosen to further characterize lesions. In addition, MR imaging is the ideal modality for evaluating the extent of retroperitoneal tumors as well as their relationship to adjacent structures and organs. The multiplanar capabilities and soft-tissue contrast resolution are significant advantages of MR over CT. This article reviews the retroperitoneal anatomy and our current imaging techniques. Disease processes that commonly affect the retroperitoneum are discussed along with their MR imaging characteristics.