Anatomy of the Colon The colon is the first 6 feet of the large intestine. It has four sections: The first section is called the ascending colon. It extends upward on the right side of the abdomen. The second section is called the transverse colon since it goes across the body to the left side. There it joins the third section, the descending colon, which continues downward on the left side. The fourth section is known as the sigmoid colon because of its S-shape. The sigmoid colon joins the rectum, which, in turn, joins the anus, or the opening where waste matter passes out of the body.

What is colorectal cancer?

Colorectal cancer is malignant cells found in the colon or rectum. The colon and the rectum are part of the large intestine, which is part of the digestive system. Because colon cancer and rectal cancers have many features in common, they are sometimes referred to together as colorectal cancer. Cancerous tumors found in the colon or rectum also may spread to other parts of the body.

Colorectal cancer is the third most common cancer in both men and women. It is estimated by the American Cancer Society that 106,370 colon and 40,570 rectal cancer cases are expected in 2004. However, the number of new cases of colorectal cancer, and the number of deaths due to colorectal cancer, have decreased, which is attributed to increased screening and polyp removal.

What are the symptoms of colorectal cancer?

The following are the most common symptoms of colorectal cancer. However, each individual may experience symptoms differently.

People who have any of the following symptoms should check with their physicians, especially if they are over 40 years old or have a personal or family history of the disease:

• a change in bowel habits such as diarrhea, constipation, or narrowing of the stool that lasts for more than a few days
  
  
• rectal bleeding or blood in the stool
  
  
• cramping or gnawing stomach pain
  
  
• decreased appetite
  
  
• vomiting
  
  
• weakness and fatigue
  
  
• jaundice (yellowish coloring) of the skin or sclera of the eye

The symptoms of colorectal cancer may resemble other conditions, such as infections, hemorrhoids, and inflammatory bowel disease. It is also possible to have colon cancer and not have any symptoms. Always consult your physician for a diagnosis.

What are the risk factors for colorectal cancer?

Risk factors may include:

What is a risk factor? A risk factor is anything that may increase a person's chance of developing a disease. It may be an activity, such as smoking, diet, family history, or many other things. Different diseases, including cancers, have different risk factors. Although these factors can increase a person's risk, they do not necessarily cause the disease. Some people with one or more risk factors never develop the disease, while others develop disease and have no known risk factors. But, knowing your risk factors to any disease can help to guide you into the appropriate actions, including changing behaviors and being clinically monitored for the disease.

• age
  Most people who have colorectal cancer are over age 50, however, it can occur at any age.
  
  
• diet
  Colorectal cancer is often associated with a diet high in fat and calories, and low in fiber.

• polyps
  Benign growths on the wall of the colon or rectum are common in people over age 50, and are believed to lead to colorectal cancer.

• personal history
  People who have had colorectal cancer, as well as ovarian, uterine, or breast cancers, have a slightly increased risk for colorectal cancer.

• family history
  People with first-degree relatives who have had colorectal cancer have an increased risk for colorectal cancer.

• ulcerative colitis
  People who have ulcerative colitis, an inflamed lining of the colon, have an increased risk for colorectal cancer.

What causes colorectal cancer?

The exact cause of most colorectal cancer is unknown, but the known risk factors listed above are the most likely causes. Less than 10 percent of colorectal cancers are caused by inherited gene mutations. People with a family history of colorectal cancer may wish to consider genetic testing. The American Cancer Society suggests that anyone undergoing such tests have access to a physician or geneticist qualified to explain the significance of these test results.

Prevention of colorectal cancer:

Although the exact cause of colorectal cancer is not known, it is possible to prevent many colon cancers with the following:

• diet and exercise
  It is important to manage the risk factors you can control, such as diet and exercise. Eating more fruits, vegetables, and whole grain foods, and avoiding high-fat, low-fiber foods, plus appropriate exercise, even small amounts on a regular basis, can be helpful.

• drug therapy
  Some studies have shown that low doses of nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, and estrogen replacement therapy for post-menopausal women may reduce the risk of colorectal cancer. Discuss this with your physician.

• screenings
  Perhaps most important to the prevention of colorectal cancer is having screening tests at appropriate ages. Because some colorectal cancers cannot be prevented, finding them early is the best way to improve the chance of successful treatment, and reduce the number of deaths caused by colorectal cancer.
  
  The following screening guidelines can lower the number of cases of the disease, and can also lower the death rate from colorectal cancer by detecting the disease at an earlier, more treatable stage.

Methods of screening for colorectal cancer:

Screening methods for colorectal cancer, for people who do not have any symptoms or strong risk factors, include the following:

• digital rectal examination (DRE) - a physician or healthcare provider inserts a gloved finger into the rectum to feel for anything unusual or abnormal.

• fecal occult blood test - a sample of stool is examined for blood. A test kit will explain how to take a sample at home. It is then returned to the physician's office to be examined.

• One of the following:
  
  
  • sigmoidoscopy - a slender, flexible, hollow, lighted tube is placed into the rectum allowing the physician to look at the inside of it and part of the colon for cancer or for polyps.
    
    
  • colonoscopy - a long, flexible, lighted tube (much longer than a sigmoidoscope) about the thickness of a finger is inserted through the rectum up into the colon, allowing the physician to see the colon lining.
    
    
  • barium enema with air contrast (Also called a double contrast barium enema.) - a fluid called barium (a metallic, chemical, chalky, liquid used to coat the inside of organs so that they will show up on an x-ray) is given into the rectum to partially fill up the colon. An x-ray of the abdomen shows strictures (narrowed areas), obstructions (blockages), and other problems.

Screening Guidelines for Colorectal Cancer

Colorectal cancer screening guidelines from the American Cancer Society for early detection include: Beginning at age 50, both men and women should follow this testing schedule: Digital rectal examination should be performed at the time of each screening sigmoidoscopy, colonoscopy, or barium enema examination. Yearly fecal occult blood test, plus: flexible sigmoidoscopy every 5 years, or colonoscopy every 10 years, or double contrast barium enema every 5-10 years People with any of the following colorectal cancer risk factors should begin screening procedures at an earlier age: strong family history of colorectal cancer or polyps (cancer or polyps in a first degree relative younger than 60 or in two first degree relatives of any age) family with hereditary colorectal cancer syndromes (familial adenomatous polyposis and hereditary non-polyposis colon cancer) personal history of colorectal cancer or adenomatous polyps personal history of chronic inflammatory bowel disease

Diagnostic procedures for colorectal cancer:

In addition to a complete medical history and physical examination, diagnostic procedures for colorectal cancer may include the following:

• digital rectal examination (DRE)
  
  
• fecal occult blood test
  
  
• sigmoidoscopy
  
  
• colonoscopy
  
  
• barium enema
  
  
• biopsy
  
  
• CEA assay (to measure a protein called carcinoembryonic antigen, which is sometimes higher in patients who have colorectal cancer)

Treatment for colorectal cancer:

Specific treatment for colorectal cancer will be determined by your physician based on:

• your age, overall health, and medical history
• extent of the disease
• your tolerance for specific medications, procedures, or therapies
• expectations for the course of the disease
• your opinion or preference

Treatment choices for the person with colon cancer depend on the stage of the tumor - if it has spread and how far. When the disease has been found and staged, your physician will suggest a treatment plan. Treatment may include:

• colon surgery
  Often, the primary treatment for colorectal cancer is an operation called a segmental resection, in which the cancer and a length of normal tissue on either side of the cancer are removed, as well as the nearby lymph nodes.

• radiation therapy
  Radiation therapy is the use of high-energy radiation to kill cancer cells either after surgery, to kill small areas of cancer that may not be seen during surgery, or instead of surgery. Radiation may also be used to ease (palliate) symptoms such as pain, bleeding, or blockage. There are two ways to deliver radiation therapy, including the following:
  
  
  • external beam radiation
    External beam radiation uses radiation from outside the body, which is focused on the cancer.
    
    
  • internal radiation therapy
    Internal radiation therapy uses small pellets of radioactive material placed directly into the cancer.
    
    
• chemotherapy
  Drugs (medications) are given into a vein or by mouth to kill cancer cells throughout the body. Studies have shown that chemotherapy after surgery can increase the survival rate for patients with some stages of colon cancer. Chemotherapy can also help relieve symptoms of advanced cancer.