Intestinal polyps are small, mushroom-like abnormalities of the intestine that may have a stalk or be flat with a stalk. They can vary from under 2 millimeters (less than 1/10 of an inch) to over 2 inches in diameter.
Certain sporadic (not inherited) intestinal polyps are a risk factor for colorectal cancer. These polyps - chiefly those classified as adenomas (growths with gland-like characteristics) - are benign, but they may become cancerous, particularly if they grow larger than an inch in diameter.
In most cases, colorectal polyps do not cause symptoms; however, they can cause intermittent bleeding or the passage of mucus with bowel movements. If they are large, they can obstruct the passage of waste material.
Adenomas account for about 70 percent of all colorectal polyps removed as part of colonoscopic examination. Adenomas are present in 30 percent of all adults over the age 50. They arise most often in the rectum and sigmoid colon.
Adenomas are described as pedunculated when they grow on a stalk that connects the head of the polyp to the bowel wall. Flatter polyps that grow directly on the wall of the bowel are called sessile.
About 85 percent are tubular (growing in microscopic tube-like patterns); 5 percent are villous (forming finger-like projections, or fronds); and 10 percent are tubulovillous (intermediate structures that contain both growth patterns). These polyps differ in their structure, texture, and microscopic characteristics; they also differ in their potential for cancerous change.
Invasive cancer develops in roughly 5 percent of all tubular (also called adenomatous) polyps. Villous polyps are less common, but about 40 percent of them become cancerous. Cancer develops in about 22 percent of all tubulo-villous polyps. The most common colorectal types, called hyperplastic polyps or hyperplastic mucosal tags, are harmless.
Scientists believe that many cancers of the large bowel arise from polyps. Thus removing these growths (polypectomy), often through a sigmoidoscope or colonoscope, is one way to prevent colorectal cancer. Because new polyps develop in nearly half of all patients who have had such growths removed, careful follow-up is necessary.
Family History: Siblings and parents of patients with colon polyps are at increased risk for colon cancer, particularly when the polyp is diagnosed before the age of 60 or - in the case of siblings - when a parent has had colon cancer.
Diet: About 90 percent of all colon cancers arise from polyps in the colon. If doctors could prevent polyps from occurring in the first place, they could reduce the incidence of cancer. In general, most physicians encourage people to eat a low-fat, high-fiber diet, to eat more fruits, vegetables, chicken and fish, and to eat less red meat.
Smoking: Smoking may also be a risk factor for colon cancer.
Obesity: In some studies, higher body mass was positively associated with an increased risk of adenomas leading to colon cancer.
Many polyps are asymptomatic; the larger the lesion, the more likely it is to cause symptoms. Rectal bleeding is by far the most frequent complaint. Blood is bright red or dark red, depending on the location of the polyp, and bleeding is usually intermittent.
Some polyps, notably large villous adenomas, may secrete copious amounts of mucus that are released through the rectum.
When a person's symptoms suggest there might be pre-cancerous or cancerous growths in the colon or rectum, the doctor will ask about the patient's medical history and then will conduct a complete exam.
In addition to checking the general signs of health (temperature, pulse and blood pressure) the doctor usually performs the following tests:
First, the doctor will insert a lubricated and gloved finger into the rectum to gently feels for any bumps. The fecal occult blood test is done on a stool sample to find if there is blood in the stool. For this test, the patient places a small amount of stool on a plastic slide or piece of special paper. The sample is then sent to a lab to be examined. If performed at home, three samples are usually taken.
The doctor may also do a flexible sigmoidoscopy to look at the rectum and the lower end of the colon. For this exam, a thin, flexible instrument with a light at the end, called a sigmoidoscope, is inserted into the rectum. After these steps, the doctor may recommend a colonoscopy.
A colonoscopy enables the doctor to see the entire length of the colon. For this exam, the doctor uses a colonoscope, which a thin, flexible tube with a light at the end. If a polyp is found, the doctor will remove a tissue (biopsy) for examination at a lab.
Polyps of the colon and rectum are treated because they produce symptoms, because they may be malignant when first discovered, or because they may become malignant later.
Small polyps can be removed with an electrocautery snare passed through a rigid or flexible sigmoidoscope, but since total colonoscopy is recommended in all patients who have a polyp, it is best to wait and do the polypectomy in a well-prepared colon during that procedure.
Large, sessile, soft, velvety lesions in the rectum are usually villous adenomas and these tumors have a high malignant potential and must be excised completely. With the patient anesthetized, this can be accomplished through the anus in most instances.
Pedunculated polyps and small sessile lesions in the sigmoid and above should be removed with biopsy forceps or an electrocautery snare passed through the colonoscope.
Depending on your medical history, age and risk factors, your physician will recommend how often to screen for colon cancer, including how often you should perform the fecal occult blood test and how frequently you should have a flexible sigmoidoscopy, colonoscopy, or other tests performed.