Imaging tests

The imaging tests used to diagnose colorectal cancer, are the ones used for screening: 

• Colonoscopy ,
• Rectosigmoscopy , 
• Computed tomographic (CT) colonography ,
• or Double-contrast barium enema .

Imaging exams permit to visualize in great detail the inside of the long muscular tube that makes the colon and rectum. 

They differ in visual acuity, so in "what they can detect", but also in the pre-exam preparation and their risks. 

Another vital difference is the possibility of performing a biopsy during the examination. For example, a positive result from virtual colonoscopy or the double contrast barium enema (DCBE) inevitably leads to the need for a colonoscopy to obtain a biopsy. 

There are other tests, used after a colorectal cancer diagnosis, that are not discussed here.
They are used to understand the stage of disease progression (e.g., MRI, positron emission tomography (PET), or computerized axial tomography.