Colorectal Cancer Imaging

Abstract

The colorectal cancer (CRC) is the most common gastrointestinal neoplasm and the third-most common cancer worldwide. The role of different imaging techniques has evolved over the last decades and they contribute to the screening, diagnosis, staging, follow-up, and treatment evaluation. A multiphase contrast enhanced CT of the thorax, abdomen and pelvis is the preferred imaging modality to stage the colorectal cancer. The protocol includes native, late arterial and portal venous phase. The CT study allows visualization of the primary tumor – its location, relation to other organs and potential invasion, fistulization and other possible complications. It can identify lymphadenopathy, peritoneal carcinomatosis and distant metastases. CT colonography allows visualization of the entire colon and the pericolonic fat and it is essential for the diagnosis of synchronous tumors with patients with incomplete colonoscopy or contraindications or refusal of colonoscopy. According to the 2016 European Society of Gastrointestinal and Abdominal Radiology (ESGAR) guidelines for imaging rectal cancer MR examination should be performed. It can show the relation of the tumor to the mesorectal fascia and to assess T stage. The MRI protocol includes T2-weighted sequences in axial, coronal and sagittal planes, diffusion-weighted sequences, which show anatomic and functional information about the tumor. The correct diagnosis of colorectal cancer and the proper reporting of different imaging characteristics are crucial for the selection of the most appropriate treatment strategies so the clinicians and radiologists should be familiar with opportunities and limitations of each method.