Numerous clinical studies, those that collect and analyze patient treatment data, have proven that the precursor lesion (a localized, structural abnormality) to colorectal cancer is the adenomatous polyp. A polyp is an abnormal growth that develops from the cells that line the colon, and protrudes into the lumen, or central passageway of the colon, which is essentially a tube. Some polyps are flat, or sessile, while others, termed peduncular, have a stalk. While there are several different types of polyps, generally only the adenomas are precancerous. They account for 50% to 60% of all polyps.
Incidence of these precancerous lesions increases with age; by age 50, one quarter of the American population will develop adenomatous polyps. They can develop anywhere in the colon but are most often found in the lower third of the large bowel.
If precancerous polyps are found and destroyed when small, they never have the opportunity to become cancerous. For this reason, the key strategy for maintaining colorectal health is a proper screening program to detect and eliminate colonic lesions before they become cancers.
Q: What are the symptoms of colorectal cancer?
The most commonly reported problem is rectal bleeding, which is a very "non-specific" symptom. This means that the bleeding can be attributed to many different causes, and frequently those with colorectal cancer may blame any bleeding they notice on hemorrhoids, fissures or other benign anal problems.
Changes in bowel habits include narrower stools or a change in frequency of bowel movements, including both constipation or diarrhea. Newly developed constipation, an enlarging abdomen, or abdominal discomfort and cramping may be caused by a colon tumor that is partially blocking the bowel.
If the cancer is located in the rectum, symptoms may include tenesmus, a feeling that you have not completely emptied after a bowel movement, bleeding or discomfort in the pelvic region.
Q: Who is most at risk for developing colorectal cancer?
A high-fat, low-fiber diet is thought to place a person at higher risk for developing colon cancer. A diet deficient in fruits and vegetables that provide fiber, and high in animal-based fats may promote colorectal cancer. Similarly, a sedentary lifestyle devoid of regular exercise, as well as tobacco smoking and excessive alcohol consumption, may contribute to other health complications and increase risk for developing colorectal cancer.
Certain diseases are believed to place individuals at higher risk. These include inflammatory bowel diseases such as ulcerative colitis and Crohn's disease, inherited polyposis syndromes like Gardner's syndrome or familial polyposis, and any of the nonpolyposis colon cancer syndromes.
Anyone with a "first degree" relative (your mom, dad or sibling) who has developed colon cancer is at increased risk. This is especially influential if their cancer developed at a younger age, i.e., less than age 50. Also, women who have experienced breast, ovarian or uterine cancer may be at increased risk for developing colon cancer.
For those with more than average risk for developing colorectal cancer a more stringent screening schedule is necessary. You are in this category if
Q: How is colorectal cancer detected?
Fecal occult blood testing (FOBT) is a simple test for detecting the presence of blood in the stool. It involves testing two samples from three consecutive stools after following a specific diet. You may be familiar with the term Hemoccultš which is the trade name for the test kit that is used. Your doctor will process the sample to determine if there is blood in the specimen which may not be visible, therefore the use of the term "occult." If evidence of bleeding is found, the next diagnostic examination would be a colonoscopy.
Flexible sigmoidoscopy is an examination of the lining of the lower two feet of your descending colon, your sigmoid colon and the rectum. The majority of colorectal cancers begin in this area of the bowel. Sigmoidoscopies are routinely performed in your doctor's office with the use of a lighted, flexible fiberoptic endoscope. Prior to the examination cleansing of the lower bowel is necessary, most often using enemas. There is only slight discomfort during the procedure. When done in the office, no sedation is required and you may drive immediately afterwards and carry out normal activities.
If an abnormality is found, a colonoscopy at a later date will be required to examine the remainder of the colon for other growths, and to remove any polyps, known as "polypectomy", or to biopsy any lesions not amenable to removal through the colonoscope.
Double-contrast barium enema is an X-ray examination using air and barium, a paste-like, opaque substance, which are inserted through the rectum by use of an enema tube. The presence of barium allows the X-rays to outline the shape and contour of the colon's lining and indicate any suspicious lesions. If found, colonoscopy will be necessary for visualization and removal or biopsy of the lesion(s). Colonoscopy involves direct visual examination of the lining of the entire colon. Like flexible sigmoidoscopy, the endoscope used is a lighted, flexible fiberoptic instrument. This examination is more extensive, however, and requires a more extensive cleansing protocol. Abnormalities such as polyps may be removed and precancerous lesions thus cured. This examination takes longer but is also minimally uncomfortable. It is performed in an endoscopy unit where sedation is available to make you more relaxed. Your blood pressure, heart rate and oxygenation are monitored during the exam. Afterwards, you will need someone to drive you home, but can eat immediately and resume all normal activities the following day.
Q: What are the pros and cons of sigmoidoscopy versus colonoscopy?
Those who favor sigmoidoscopy believe that if no polyps are present in the sigmoid colon they are unlikely to exist in the remainder of the colon and therefore, feel that colonoscopy for such individuals is unnecessary.
The opposing viewpoint takes nothing for granted, believing that the only way to be certain the colon is free of precancerous polyps is to examine it completely.
The motivating factor behind this controversy is often economic. Colonoscopy is a more involved and expensive procedure than sigmoidoscopy. Those responsible for paying for colorectal screening procedures usually support the use of sigmoidoscopy, if anything, over the performance of routine full colonic examination.
Q: What is the recommended frequency of screening for colorectal disease in "normal risk" individuals?
Q: How does this vary for high risk individuals?
Q: What happens if I am diagnosed with colorectal cancer?
The only tumor location that prohibits anastomosis is the very distal rectum, within a finger's reach of the anus. Those few with tumors in this location have a number of treatment options available; these are discussed in the section on rectal cancer. Some patients may unfortunately require a complete rectal resection, also called an abdominoperineal resection, and a permanent colostomy.
Your surgeon performs a colostomy to create a small opening, or stoma, in the abdominal wall through which feces exits the body. Depending on the size of the rectal tumor it may be possible to avoid this radical operation and treat the tumor in a way which does not require colostomy. But, if a stoma is necessary, specially trained nurses, in addition to your physician, will assist in its initial care. Today, this is simpler than in the past. The stoma nurse is a professional trained in the care and teaching of patients requiring colostomy. He or she is available for questions before or after your surgery at Columbia Presbyterian, and is an invaluable source of information, medical care and support.
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