Rectal Cancer

Rectal cancer is a type of cancer that occurs in the cells in the rectum — the last section of the large intestine (colon), which is the lower part of your digestive system. During digestion, food moves through the stomach and small intestine into the colon. The colon absorbs water and nutrients from the food and stores waste matter (stool). Stool moves from the colon into the rectum before it leaves the body.

Rectal cancer is often grouped together with colon cancer, and together they are called colorectal cancer.

Rectal cancer most often begins in the cells that line the inside of the rectum. Rectal cancer often first forms as precancerous polyps.

Many cases of colorectal cancer have no symptoms. If symptoms are present, they may include blood in the stool, diarrhea, constipation or other changed in bowel habits, and weight loss for no known reason.

Colorectal cancer is the third most common type of cancer in men and women in the United States. It is a leading cause of cancer death, but deaths from colorectal cancer have decreased in recent years with the widespread use of regular screenings, including colonoscopies and fecal occult blood tests, which check for blood in the stool.

In most cases, the cause of colorectal cancer is not clear. Doctors know that colorectal cancer occurs when healthy cells in the colon become altered. Healthy cells grow and divide in an orderly way to keep your body functioning normally. But when a cell is damaged and becomes cancerous, cells continue to divide — even when new cells are not needed. These cancer cells can invade and destroy normal tissue nearby, and cancerous cells can travel to other parts of the body.

Factors that may increase your risk of colorectal cancer include:

• older age. The majority of people diagnosed with colon cancer are older than 50 years. Colorectal cancer can occur in younger people, but it occurs much less frequently.
• African-American race. African-Americans have a greater risk of colorectal cancer than do people of other races.
• a personal history of colorectal cancer or polyps. If you have already had colon cancer or adenomatous polyps, you have a greater risk of colorectal cancer in the future.
• inflammatory intestinal conditions. Chronic inflammatory diseases of the colon, such as ulcerative colitis and Crohn's disease, can increase your risk of colorectal cancer.
• inherited syndromes that increase colorectal cancer risk. Genetic syndromes passed through generations of your family can increase your risk of colorectal cancer. These syndromes include familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer, which is also known as Lynch syndrome.
• family history of colorectal cancer and colon polyps. You're more likely to develop colorectal cancer if you have a parent, sibling or child with the disease. If more than one family member has colorectal cancer or rectal cancer, your risk is even greater. In some cases, this connection may not be hereditary or genetic. Instead, cancers within the same family may result from shared exposure to an environmental carcinogen or from diet or lifestyle factors.
• low-fiber, high-fat diet. Colon cancer and rectal cancer may be associated with a diet low in fiber and high in fat and calories. Research in this area has had mixed results. Some studies have found an increased risk of colorectal cancer in people who eat diets high in red meat. Diets high in vegetables, fruits, and whole grains have been linked with a decreased risk of colorectal cancer, but fiber supplements do not seem to help. It's not clear if other dietary components (for example, certain types of fats) affect colorectal cancer risk.
• a sedentary lifestyle. If you are inactive, you are more likely to develop colorectal cancer. Getting regular physical activity may reduce your risk of colorectal cancer.
• diabetes. People with diabetes and insulin resistance may have an increased risk of colorectal cancer.
• obesity. People who are very overweight or obese have an increased risk of colorectal cancer and an increased risk of dying of colorectal cancer when compared with people considered normal weight.
• smoking. People who smoke cigarettes may have an increased risk of colorectal cancer.
• alcohol. Heavy use of alcohol may increase your risk of colorectal cancer.
• radiation therapy for cancer. Radiation therapy directed at the abdomen to treat previous cancers may increase the risk of colorectal cancer.

See your doctor for rectal bleeding, a change in bowel habits, narrow stools, or a feeling that the bowel does not empty, and keep up with recommended screening. Early detection greatly improves outcomes.