Can a ct scan of abdomen detect cancer?

Yes, but: Yes it can, but not always, and not all kinds of cancer. There are many variables: whether or not IV contrast is used, whether or not oral contrast is used, the timing of the scan after contrast, etc. A radiologist can tailor the scan to look for certain tumors if they know what kind you are looking for. But an obvious tumor is usually visible on most ct scans.

Sometimes. : It depends on many factors, the size of the cancer, the organ it involves, technical factors with the study, etc. There are many variables. Remember each cancer starts as a single cell, so we can never completely exclude the diagnosis even when a ct is completely normal. Pet/ct can show cancers that are virtually impossible to see on ct, even with contrast.