Preoperative evaluation of colorectal cancer using CT colonography, MRI, and PET/CT

Imaging studies are a major component in the evaluation of patients for the screening, staging and surveillance of colorectal cancer. This review presents commonly encountered findings in the diagnosis and staging of patients with colorectal cancer using computed tomography (CT) colonography, magnetic resonance imaging (MRI), and positron emission tomography (PET)/CT colonography. CT colonography provides important information for the preoperative assessment of T staging. Wall deformities are associated with muscular or subserosal invasion. Lymph node metastases from colorectal cancer often present with calcifications. CT is superior to detect calcified metastases. Three-dimensional CT to image the vascular anatomy facilitates laparoscopic surgery. T staging of rectal cancer by MRI is an established modality because MRI can diagnose rectal wall laminar structure. N staging in patients with colorectal cancer is still challenging using any imaging modality. MRI is more accurate than CT for the evaluation of liver metastases. PET/CT colonography is valuable in the evaluation of extra-colonic and hepatic disease. PET/CT colonography is useful for obstructing colorectal cancers that cannot be traversed colonoscopically. PET/CT colonography is able to localize synchronous colon cancers proximal to the obstruction precisely. However, there is no definite evidence to support the routine clinical use of PET/CT colonography.