Colorectal cancer is also known as colon cancer, rectal cancer or bowel cancer and is the development of cancer in the colon or rectum (parts of the large intestine).

Symptoms may include blood in the stool, a change in bowel movements, weight loss, and constant fatigue.

Risk factors for colorectal cancer include lifestyle, older age, and inherited genetic disorders. Other risk factors include diet, smoking, alcohol, lack of physical activity, family history of colon cancer and colon polyps, presence of colon polyps, race, exposure to radiation, and even other diseases such as diabetes and obesity. Genetic disorders only occur in a small fraction of the population. Other diseases such as inflammatory bowel disease, which includes Crohn's disease and ulcerative colitis, can increase the risk of colorectal cancer.

Bowel cancer may be diagnosed by obtaining a sample of the colon during a sigmoidoscopy or colonoscopy. Screening is recommended starting from the age of 50 to 75 and is effective for preventing and decreasing deaths from colorectal cancer.

Treatments used for colorectal cancer may include some combination of surgery, radiation therapy, chemotherapy and targeted therapy. Cancers that are confined within the wall of the colon may be curable with surgery while cancer that has spread widely are usually not curable, with management focusing on improving quality of life and symptoms.

Globally, colorectal cancer is the third most common type of cancer making up about 10% of all cases. It is more common in developed countries, where more than 65% of cases are found, and less common in women than men.