Colorectal cancer: features and investigation

Colorectal cancer is a common malignancy affecting 35,000 people a year in the UK. Most cancers are sporadic but a few, occurring at young age, have a clear genetic basis. The majority are in the rectum or rectosigmoid and give rise to symptoms of rectal bleeding, often with a looser or more frequent stool. Right-sided cancers typically give rise to anaemia, because the blood in the stool is occult and unnoticed by the patient. Almost all the symptoms of malignancy can also be caused by benign disease. Diagnosis relies on luminal imaging, with colonoscopy being the gold standard. Pre-operative staging should include imaging of the liver and chest with computed tomography. For rectal cancers, magnetic resonance scanning of the pelvis provides accurate information about the local tumour and nodal status, and is used to inform decisions regarding pre-operative chemoradiotherapy. All colorectal cancers should be discussed at multidisciplinary meetings to enable optimum treatment to be determined.