Colorectal cancer

The colon is part of the bodys digestive system. The digestive system removes and processes nutrients (vitamins, minerals, carbohydrates, fats, proteins, and water) from foods and helps pass waste material out of the body. The digestive system is made up of the esophagus, stomach, and the small and large intestines. The first 6 feet of the large intestine are called the large bowel or colon. The last 6 inches are the rectum and the anal canal. The anal canal ends at the anus (the opening of the large intestine to the outside of the body).

Colorectal cancer, also called colon cancer or bowel cancer, includes cancerous growths in the colon, rectum and appendix. It is the third most common form of cancer and the second leading cause of death among cancers in the Western world. Many colorectal cancers are thought to arise from adenomatous polyps in the colon. These mushroom-like growths are usually benign, but some may develop into cancer over time. Diagnosis is by colonoscopy. Therapy is usually through surgery, with many cases also requiring chemotherapy.

Risk factors include the following:

Age. The risk of developing colorectal cancer increases with age. Most cases occur in the 60s and 70s, while cases before age 50 are uncommon unless a family history of early colon cancer is present.
History of cancer. Women who have had cancer of the ovary, uterus, or breast are at higher risk of developing colorectal cancer.
Heredity:
Family history of colon cancer, especially in a close relative before the age of 55 or multiple relatives
Familial adenomatous polyposis (FAP) carries a near 100% risk of developing colorectal cancer by the age of 40 if untreated
Hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch syndrome
Long-standing ulcerative colitis or Crohn's disease of the colon, approximately 30% after 25 years if the entire colon is involved
Smoking. Smokers are more likely to die of colorectal cancer than non-smokers. An ACS study found that "Women who smoked were more than 40% more likely to die from colorectal cancer than women who never had smoked. Male smokers had more than a 30% increase in risk of dying from the disease compared to men who never had smoked."
Diet. Studies show that a diet high in red meat (Chao et al 2005) and low in fresh fruit, vegetables, poultry and fish increases the risk of colorectal cancer. In June 2005, a study by the European Prospective Investigation into Cancer and Nutrition suggested that diets high in red and processed meat, as well as those low in fiber, are associated with an increased risk of colorectal cancer. Individuals who frequently ate fish showed a decreased risk. However, other studies have cast doubt on the claim that diets high in fiber decrease the risk of colorectal cancer. The nature of the relationship between dietary fiber and risk of colorectal cancer remains controversial.
Physical inactivity. People who are physically active are at lower risk of developing colorectal cancer.
Virus. Exposure to some viruses (such as particular strains of human papilloma virus) may be associated with colorectal cancer.

Possible signs and symptoms of colon cancer include

A change in bowel habits.
Blood (either bright red or very dark) in the stool.
Diarrhea, constipation, or feeling that the bowel does not empty completely.
Stools that are narrower than usual.
Frequent gas pains, bloating, fullness, or cramps.
Weight loss for no known reason.
Feeling very tired.
Vomiting.