I am 61 have had a complete hystectomy three and half years ago. Two years ago I had pelvic pain first went to ObGyn she couldn't find anything, she recommended I see my Gastrolorgist. When I went to see him he ordered a CT scan. He said scan was normal. Now two years later I was diagnosed with cancer of rectum. My question is why it wasn't picked up in the CT scan from two year ago?