Globally, cancer of the colon and rectum is the third leading cause of cancer in males and the fourth leading cause of cancer in females. The frequency of colorectal cancer varies around the world. It is common in the Western world and is rare in Asia and Africa. In countries where the people have adopted western diets, the incidence of colorectal cancer is increasing.

The colon is the part of the digestive system where the waste material is stored. The rectum is the end of the colon adjacent to the anus. Together, they form a long, muscular tube called the large intestine (also known as the large bowel). Tumors of the colon and rectum are growths arising from the inner wall of the large intestine. Benign tumors of the large intestine are called polyps. Malignant tumors of the large intestine are called cancers. Benign polyps do not invade nearby tissue or spread to other parts of the body.

Benign polyps can be easily removed during colonoscopy and are not life-threatening. If benign polyps are not removed from the large intestine, they can become malignant (cancerous) over time. Most of the cancers of the large intestine are believed to have developed from polyps. Cancer of the colon and rectum (also referred to as colorectal cancer) can invade and damage adjacent tissues and organs. Cancer cells can also break away and spread to other parts of the body (such as liver and lung) where new tumors form. The spread of colon cancer to distant organs is called metastasis of the colon cancer. Once metastasis has occurred in colorectal cancer, a complete cure of the cancer is unlikely.

Cancer of the colon and rectum can exhibit itself in several ways. If you have any of these symptoms, seek immediate medical help.
You may notice bleeding from your rectum or blood mixed with your stool.

• People commonly attribute all rectal bleeding to hemorrhoids, thus preventing early diagnosis owing to lack of concern over "bleeding hemorrhoids."

• Rectal bleeding may be hidden and chronic and may show up as an iron deficiency anemia.

• It may be associated with fatigue and pale skin.

• It usually, but not always, can be detected through a fecal occult (hidden) blood test, in which samples of stool are submitted to a lab for detection of blood.

If the tumor gets large enough, it may completely or partially block your colon. You may notice the following symptoms of bowel obstruction:

• Abdominal distension: Your belly sticks out more than it did before without weight gain.

• Abdominal pain: This is rare in colon cancer. One cause is tearing (perforation) of the bowel. Leaking of bowel contents into the pelvis can cause inflammation (peritonitis) and infection.

• Unexplained, persistent nausea or vomiting

• Unexplained weight loss

• Change in frequency or character of stool (bowel movements)

• Small-caliber (narrow) or ribbon-like stools

• Sensation of incomplete evacuation after a bowel movement

• Rectal pain: Pain rarely occurs with colon cancer and usually indicates a bulky tumor in the rectum that may invade surrounding tissue.

-precancerous changes ususally do not cause any symptoms-
-most common symptom is abnormal bleeding-
-bleeding may start and stop between regular menstrual periods-
-bleeding after sexual intercourse-
-bleeding after douching-
-bleeding after pelvic exam-
-menstrual bleeding may last longer and be heavier than usual-
-bleeding after menopause-
-increased vaginal discharge-

Colon cancer does not always present symptoms in the early stages. Colon cancer symptoms usually do not appear until the disease has progressed into an advanced stage. This makes colon cancer screening highly valuable -- it can detect colon cancer in the early stages, before symptoms begin to appear.
Blood in Stool:
Blood in the stool is a common symptom of colon cancer, but you can't always actually see blood that may be in the stool. Tests like the fecal occult blood test (FOBT) detect blood in the stool that may be unseen to the naked eye. It is also associated with less severe health problems, such as hemorrhoids and anal fissures.

1. Age

Age is the number one risk factor for colon cancer. Does that mean that age causes colon cancer? Not directly. It's just that by age age 50, one in four people has polyps. You'll learn more about polyps and their role in #14.

2. Alcohol

Research has indicated that alcohol increases colorectal cancer risk. Research has also shown that it lowers it, or that it has no effect at all. So which is right? All of it may be. The key appears to be what kind of alcohol you're drinking.

3. Diabetes

A study published in the journal Gastroenterology found that insulin dependency contributes to colon cancer development. In general, diabetics are up to 40% more likely to develop colon cancer than people who don't have diabetes.

4. Diet

Diets high in fat and cholesterol (especially from animal sources) have been found to cause colon cancer. Low-fiber diets have also been associated with increased risk, but the research isn't as clear.

5. Environment

Research has shown that environment can play a big part in colon cancer development. Where you live, who's around you, your occupation, and even when you work may all influence your risk of developing colon cancer.

6. Ethnicity, Race, and Social Status

Does colorectal cancer afflict everyone equally or are some groups of people more likely to be diagnosed than others? The reasons are varied, but some groups get colorectal cancer more often than others. Ethnicity, race, and social status all play a part.

7. Family Medical History

Most colon cancer occurs in people with no family history of the disease. But, colon cancer can run in the family. Whether you're at increased risk depends on which family member was diagnosed and at what age.

8. Gender

You may have heard that men are more likely to get colorectal cancer than women. You may have heard it the other way around, too. Both statements can be true depending on the context.

9. Genetics

Researchers estimate that about 25% of colon cancer cases have some sort of genetic link. Examples of the most common genetic causes of colon cancer include mutations leading to FAP (familial adenomatous polyposis) and HNPCC (hereditary non-polyposis colorectal cancer).

10. Inflammatory Bowel Disease (IBD)

Inflammatory bowel disease, often characterized by conditions such as ulcerative colitis and Chron's disease, increases the risk of developing colorectal cancer. In general, the longer a person has had inflammatory bowel disease, the greater his or her chance of developing colorectal cancer.

11. Lack of Exercise

There's no denying that exercise is good for you. The couch potato in me would like to see a study every once in a while declaring otherwise, but that just doesn't happen. Research has shown that a sedentary lifestyle contributes to colon cancer development.

12. Obesity

Nobody likes to have the word obese thrown at them. But, obesity is a medical term that indicates someone exceeds their recommended weight, one step beyond simply being overweight. And the answer to the question is yes, obesity does increase colon cancer risk.

13. Personal Medical History

Your personal medical history can significantly impact your chances of developing colorectal cancer. A medical history that includes polyps, bowel inflammation, or certain cancers is particularly relevant.

14. Polyps

Virtually all colon cancer develops from adenomatous polyps in the colon, generally referred to simply as colon polyps. A personal or family history of polyps puts you at higher risk for colon cancer.

15. Smoking

Long-term cigarette smoking causes colon cancer for two main reasons. First, inhaled or swallowed tobacco smoke transports carcinogens to the colon. Second, tobacco use appears to increase polyp size.
Now that you have a good handle on what causes colon cancer, why not learn what prevents it? Top 10 Colon Cancer Prevention Tips provides simple, straightforward advice for protecting yourself and your loved ones from colon cancer.
-a change in bowel habits-
-diarrhea, constipation, or feeling that the bowel does not empty completely-
-blood (either bright red or very dark) in the stool-
-general abdomnal discomfort (frequent gas pains, bloating, fullness, and/or cramps)-
-weight loss with no known reason-
-constant tiredness-
-vomiting-