Polyps of the Colon and Rectum
A polyp is a projecting growth of tissue from the wall of a hollow space, such as the intestines.
Polyps also may grow inside the nose (nasal polyps).
Polyps that grow on the intestinal or rectal wall protrude into the intestine or rectum and may be noncancerous (benign), precancerous (adenomatous), or cancerous (malignant carcinoma). Polyps vary considerably in size, and the bigger the polyp, the greater the risk that it is cancerous or likely to become cancerous (that is, they are precancerous). Polyps may grow with or without a stalk (a thin piece of tissue that joins the polyp to the intestinal wall, similar to how the neck joins the head to the body). Polyps without a stalk are more likely to be cancerous than those with a stalk.
There are many types of polyps but doctors typically divide them into
Adenomatous polyps, which consist primarily of glandular cells that line the inside of the large intestine, are likely precancerous.
Nonadenomatous polyps can develop from many cell types, including the nonglandular cells that line the intestine, fat cells, and muscle cells. Some nonadenomatous polyps are caused by other disorders, for example the inflammatory polyps that develop in people with chronic ulcerative colitis. Nonadenomatous polyps are less likely to be precancerous.
Some polyps are the result of hereditary conditions, such as familial adenomatous polyposis and Peutz-Jeghers syndrome.
In Peutz-Jeghers syndrome,people have many small polyps in the stomach, small intestine, and large intestine. They also have numerous bluish black spots on their face, inside their mouth, and on their hands and feet. The spots tend to fade by puberty except for those inside the mouth. People with Peutz-Jeghers syndrome have an increased risk of developing cancer in many organs, particularly the pancreas, small intestine, colon, breast, lung, ovary, and uterus.
Most polyps do not cause symptoms. When they do, the most common symptom is bleeding from the rectum. A large polyp may cause cramps, abdominal pain, obstruction, or intussusception (one segment of the intestine slides into another, much like the parts of a telescope). Large polyps with tiny, fingerlike projections (called villous adenomas) may excrete water and salts, causing excessive watery diarrhea that may result in low levels of potassium in the blood (hypokalemia). Rarely, a rectal polyp on a long stalk drops down and dangles through the anus.
A doctor may be able to feel polyps by inserting a gloved finger into the rectum, but usually polyps are discovered when colonoscopy is done to examine the entire large intestine. This complete and reliable examination is done because more than one polyp is usually present and any may be cancerous. Colonoscopy also allows a doctor to do a biopsy (removal of a tissue sample for examination under a microscope) of any area that appears cancerous and remove polyps.
Doctors generally recommend removing all polyps from the large intestine and rectum because of their potential to become cancerous. Polyps are removed during a colonoscopy procedure using a cutting instrument or an electrified wire loop. If a polyp has no stalk or cannot be removed during colonoscopy, abdominal surgery may be needed.
If a polyp is found to be cancerous, need for additional treatment depends on whether the cancer is likely to have spread. The risk of spread is determined by microscopic examination of the polyp. If the risk is low, no further treatment is necessary. If the risk is high, particularly if the cancer has invaded the polyp’s stalk, the affected segment of the large intestine is removed surgically, and the cut ends of the intestine are rejoined (see also Treatment of Colorectal Cancer).
When a person has a polyp removed, doctors do colonoscopy to examine the entire large intestine and rectum. Colonoscopies are done once a year for 2 years and then at different intervals depending on factors such as the number, size, and type of the polyps. In some situations, doctors may recommend colonoscopy be done every 2 to 3 years, and in others every 5 years. If colonoscopy cannot be done because the person's large intestine has become narrow, a barium enema may be used to view the large intestine on x-ray.