Colorectal cancer includes cancers of both the large intestine (colon), the lower part of your digestive system, and the rectum.
Most colon and rectal cancers begin as small, noncancerous (benign) clumps of cells called adenomatous polyps. Over time some of these polyps become cancerous.
Polyps may be small and produce few, if any, symptoms, so it's important to get regular screening tests to help prevent colorectal cancer. If signs and symptoms of cancer do appear, they may include a change in bowel habits, blood in your stool, persistent cramping, gas or abdominal pain.
Colorectal cancer is the second-leading cause of cancer-related deaths. Only lung cancer claims more lives.
Still, there's good news about colorectal cancer. Screening tests, along with a few simple changes in your diet and lifestyle, can dramatically reduce your overall risk of developing the disease.
Signs and symptoms
Like many people with colorectal cancer, you may have no symptoms in the early stages of the disease. When symptoms appear, they'll likely vary, depending on the cancer's size and location in your large intestine. In some cases, your symptoms may result from a condition other than cancer, such as inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), and sometimes diverticulosis or diverticulitis. Like colorectal cancer, these conditions are treatable.
See your doctor if any of the following signs and symptoms persist for more than a couple of weeks:
Blood in your stool may be a sign of cancer, but it can also indicate other conditions. Bright red blood you notice on bathroom tissue may come from hemorrhoids or minor tears (fissures) in your anus, for example.
Normally, hemorrhoids don't bleed consistently over a period of weeks. If your bleeding is prolonged, talk to your doctor.
In addition, certain foods, such as beets or red licorice, can turn your stools red. Iron supplements and some anti-diarrheal medications may make stools black. Still, it's best to have any sign of blood or change in your stools checked promptly by your doctor.
Cancer affects your cells, the basic units of life. Healthy cells grow and divide in an orderly way to keep your body functioning normally. But sometimes this growth gets out of control — cells continue dividing even when new cells aren't needed. In the colon and rectum, this exaggerated growth may cause pre-cancerous polyps (adenomas, or adenomatous polyps) to form in the lining of your intestine. Over a long period of time — spanning up to several years — some of these polyps may become cancerous. In later stages of the disease, cancerous polyps may penetrate the colon walls and spread (metastasize) to nearby lymph nodes or other organs.
Polyps can occur anywhere in your large intestine, the muscular tube that forms the last part of your gastrointestinal (GI) tract. The colon comprises the upper 4 to 6 feet of your large intestine, and the rectum makes up the lower 8 to 10 inches. Your colon absorbs water, salt and other minerals from food and stores waste until it's eliminated from your body.
Polyps are either mushroom-shaped or flat and may be large or small. There are also several different types of colon polyps. Among the most common are: