Imaging Tests for Colorectal Cancer

If cancer is found, some imaging tests may be used to identify how far the cancer has spread.

Rectal ultrasound is an examination in which a device is inserted into the rectum. This device produces sound waves that are reflected by tissues of the rectum and nearby organs. The pattern of sound wave echoes is detected and analyzed by a computer to create an image of the rectum. Ultrasound may be used to see how deeply a rectal cancer has spread.

Computed tomography (CT) scan is an examination in which an x-ray beam is rotated around the body, to produce a series of two-dimensional images. A computer combines these images to produce a detailed, cross-sectional image map. This allows the physician to find out if a colorectal cancer has spread outside the bowel to other organs, such as the liver.

Magnetic resonance imaging (MRI) is an examination, which uses radio waves and strong magnets to scan tissues. The patterns are then taken by a computer and translated into a detailed image. MRIs can provide more detailed images than CT scans, and can also be used to detect the spread of colorectal cancer to the liver and other organs in the abdomen.