computed tomography colonography
Meaning of computed tomography colonography: A scan that builds a walk-through view of the large bowel from x-ray slices, avoiding the camera but not the preparation.
Definition of computed tomography colonography
Computed tomography colonography is a scan that examines the large bowel using x-ray slices rather than a camera. The bowel is inflated with gas, a fast scanner records the abdomen, and software reconstructs the images into flat cross sections and a three-dimensional view resembling the inside of the bowel. It is used to look for polyps and cancer.
How does the examination work?
The bowel must be empty, so the same cleansing preparation used before a camera examination is taken beforehand. A thin tube in the rectum then inflates the bowel with carbon dioxide, which absorbs quickly afterward and causes less lingering discomfort than air. The scan itself takes seconds and is repeated with the person lying face up and face down, so that fluid and residue shift and cannot hide a lesion. No sedation is needed and normal activity resumes immediately.
How does it compare with a camera examination?
| CT colonography | Colonoscopy | |
|---|---|---|
| Bowel preparation | Required | Required |
| Sedation | None | Usual |
| Perforation risk | Very low | Low but higher |
| Tissue sampling | Not possible | Done during the test |
| Findings outside the bowel | Seen | Not seen |
What are the practical trade-offs?
The decisive limitation is that nothing can be removed. If a colon polyp is found, a camera examination has to follow, so one preparation becomes two unless both are arranged for the same day. The scan is less reliable for flat lesions and for anything small, and residual stool can mimic a polyp, which is what the second position is intended to resolve.
When is it chosen?
Most often when a camera examination is incomplete, because the scope could not pass a narrowing or a bend, and the rest of the colon still needs to be seen. It also suits people for whom sedation carries particular risk, those taking blood thinners that complicate biopsy, and those who decline the camera. Against those advantages sits a radiation dose, small but not zero, which weighs differently for a test repeated over decades of screening than for a single diagnostic scan.
Also known as
Used in a sentence
Computed tomography colonography was arranged after the scope could not pass the stricture.
Good to know
Nothing can be sampled or removed during the scan, so a polyp found on it requires a subsequent camera examination and a second bowel preparation unless both are arranged for the same day.
Word origin
Where “computed tomography colonography” comes from
Colonography joins the Greek kolon, the large bowel, with graphein, meaning to write or record.