New radiographic techniques for colorectal cancer.

Before surgical staging and resection, patients with primary colorectal cancer undergo a thorough diagnostic evaluation. The initial imaging study to identify a primary site of disease often is endoscopy, which frequently is supplemented with a double contrast barium enema. Once the presence of colorectal cancer has been established, new radiographic imaging techniques, including computed tomography (CT), magnetic resonance imaging (MRI), and special ultrasound (US) may be used. Clinical questions addressed by these special imaging techniques include detection of liver and lymph metastases and clarification of local extent of disease.