Would colorectal cancer show up in pelvic CT scan?

Maybe. Sometimes - it needs to be big enough to be seen. Early colon cancer, which is when we want to find and treat it may not be seen on any imaging.
Rarely. The cancer would have to be quite large to show up on a pelvic ct scan. A colonoscopy is a much better test for colorectal cancer. Some centers are using a special kind of ct scan called "ct colonography" to dected colorectal cancer.
Not necessarily. Colon extends far outside the pelvic area and considerable parts of the colon would not be subject to imaging in a pelvic ct. Presence of feces in the colon also limits the ability of ct examination to detect colon cancer.
Yes, when it is big. It can be shown up in a ct scan when the size is large enough and by then the chance is probably it is already giving you symptoms like abdominal pain/cramping, change in bowel movement, etc. Small polyps or small tumor in colon would not be able to be picked up on ct scan and colonosocpy is the best modality to screen for colon cancer.

Related Questions

I am required to have a pelvic CT scan once a year as follow-up to colorectal cancer treatment. Are double scans without and one with contrast needed?

How long ago. Was your colon or rectal cancer? The protocol for doing with/without contrast (? Vascular and endoluminal?) may be evolving awy from the risk vs need for the without IV contrast. If it is 5 years since, and it was rectal cancer, I would stop scans.

Scared I've colorectal cancer. Had recent abd x-ray, abd CT w/ contrast, and ab ultrasound. Do these rule out the possibility of late stage cancer?

Yes. However, they do not rule out the possibility of early colon cancer. Colonoscopy is the standard test done for early detection of colon cancer and is recommended for patients with family history of colon cancer even at younger ages (less than 50). Is there any reason you are specifically scared of having colorectal cancer? Talk to your doc about your fears as well as symptoms.

Can colorectal cancer be diagnosed by CT and barium enema?

No. You need a biopsy for diagnosis. Ct and barium enema can be highly suggestive, but pathology is required.
Colonoscopy. Ct and barium enema can be use for diagnosis but does not allow for a biopsy to confirm the etiology of the lesion. Planning and extent for surgery is based on endoscopy ie polyposis, synchronous lesions, etc. Mcolonoscopy would be done after age 35 every 5 years.

What stage of colorectal cancer would a normal ABD CT rule out? If I had colorectal cancer w/ a normal CT does that mean only early stage is possible

CT scans NOT diagno. CT scans of the abdomen, no matter how "well" they are performed, are NOT diagnostic of colon cancer. Only a (colonoscopic) biopsy & (surgical) staging can do that. Thus, your question is a non-starter... colorectal cancer cannot be "ruled out" from a CT scan; while CT scan can help plan a staging procedure (& a normal CT scan is reassuring), only an oncologist can stage cancer if it exists.