A local colon or rectal cancer may cause changes in colorectal functions (diarrhea, constipation, difficulty in defecating, flatulence), blood in faeces, abdominal pain, nausea, vomiting and general fatigue. A local cancer may also be fully asymptomatic.
Colorectal cancer may be discovered in a faecal examination if a microscopic amount of blood is found. Colon and rectal cancer are verified by taking a biopsy in connection with colonoscopy. Tumor staging is normally investigated through computed tomography. The local staging of rectal cancer can be revealed most accurately through magnetic resonance imaging.