Family doctor

What does a polyp look like?

Polyps are abnormal growths growing in from the lining of the large intestine (colon) and protruding into the intestinal canal (lumen). Polyps vary in their shape, size and location within the large intestine. They may be simple or multiple. Some polyps are flat or carpet-like, spreading over the mucosal surface of the bowel. Some have a short stalk or pedicle.

Polyps are one of the most common conditions affecting the colon and rectum, occurring in 15-20 percent of the adult population.

Most polyps are benign. The relationship of certain polyps to cancer is well established.

What are the symptoms?

Although polyps are very common they rarely produce symptoms and usually are discovered by chance at the time of colonscopy or x-ray of the bowel. Larger polyps however may occasionally cause bleeding, usually as blood mixed in the stool, mucus discharge, alteration in bowel function, or in rare cases abdominal pain.

Adenomatous Polyps (adenoma)

There are different varieties of polyps but those associated with bowel cancer are termed adenomatous polyps or simply adenomas. This variety of polyp is important because there is strong evidence that some adenomas are considered at risk of developing bowel cancer. The risk is difficult to quantify. It varies from patient to patient and usually requires periodic surveillance by colonoscopic examination of the large bowel which permits inspection of the entire colon.

The colon can also be indirectly examined using the barium enaema x-ray technique. This examination uses a barium solution to coat the colon lining. X-rays are taken, and unsuspected polyps are frequently found but cannot be removed by this technique.

Although checking the stool for microscopic blood is an important test for colon and rectal disorders, a negative test DOES NOT rule out the presence of polyps. The discovery of one polyp necessitates a complete colon inspection since at least 30 percent of these patients will have additional polyps.

Pre-cancer and cancer adenomas

When polyps are pre-cancerous they are composed of abnormal, rapidly dividing cells whose suspicious appearance and behaviour can only be accurately recognised by the pathologist when examined under the microscope. Therefore, when polyps are discovered they are best removed (polypectomy) so that they can be carefully examined and classified by a pathologist. It may take up to 12 years for a benign adenoma to become an invasive cancer. Large adenomas (greater than 2cms in diameter) are always suspected of having developed a small focus of cancer until proven otherwise by the pathologist.

Who is at risk?

People who have suspicious bowel symptoms (especially bleeding) and are approaching 40 years of age or older may need a colonoscopic examination.

Other people at risk include those with a significant family history of one or more first degree relatives (father, mother, brother or child) who have had bowel cancer, and to a lesser extent those with second degree relatives (uncles, aunts, grandparents) who have had bowel cancer.

Patients who have had a previous adenoma or cancer successfully treated have a risk of developing polyps which continues through their life. Familial Adenomatous Polyposis (FAP) is a rare inherited disorder in which some members of the family will develop hundreds of polyps ultimately causing bowel cancer if not treated appropriately.

Do polyps need to be treated?

Since there is no foolproof way to predicting whether or not a polyp is or will become malignant, total removal of all polyps is advised. The vast majority of polyps can be removed by snaring with a wire loop passed through the colonoscope. Small polyps can be destroyed simply by touching them with a coagulating electrical current. Up to 95 percent of polyps can be safely and completely removed by colonoscopy.

Most colon examinations using the flexible colonoscope including polyp removal can be performed on an outpatient basis with minimal discomfort. Large polyps may require more than one treatment for complete removal. Some polyps cannot be removed because of their size or position and surgery is then indicated.

Future checks

Once a polyp is completely removed its recurrence is very unusual. However, the same factors that cause the polyp to form are still present. New polyps will develop in at least 30 percent of people who have previously had polyps. For this reason patients should have regular examinations of the bowel. The frequency of the examinations varies and this needs to be discussed with the doctor who performed the colonoscopy.