Colon cancer. Frontal X-ray of the large intestine of a patient with cancer of the sigmoid colon. The patient was given a barium enema prior to the X-ray to show up any abnormalities. The irregular filling of the sigmoid colon with the barium (white) shows the presence of a tumour (at upper left of the white region) in the large intestine. The sigmoid colon is the last part of the large intestine before the rectum. Symptoms of colon cancer include rectal bleeding and abdominal pain. Risk factors include a diet high in animal fat and low in fibre and a sedentary lifestyle. Treatment is with surgery to remove the affected area.