Wouldnt a blood test or cat scan show stomach or colon cancer.?

Scanning for Cancer: Good morning: not necessarily. Blood tests for cancer are not very specific and not too reliable. A ct scan can pick up anatomical abnormalities but if the tumor is not large it may not be easily identifiable. I would ask for more information on what stimulates your question. If you are truly concerned have you asked for an mri? Or a gastroenterology consultation?

Not if early: A ct is not sensitive enough to find very small colon growths. There is a blood test the CEA that is high in some cancers, but usually only when quite advanced and not specific to colon cancer. Now, a ct might suggest a colon cancer, however, colonoscopy is considered the gold standard for detecting colon growths. There is research into high definition ct but it is not considered a standard.