A polyp is a growth of tissue from the intestinal or rectal wall that protrudes into the intestine or rectum and may be noncancerous (benign) or cancerous (malignant). 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. Polyps without a stalk are more likely to be cancerous than those with a stalk. Adenomatous polyps, which consist primarily of glandular cells that line the inside of the large intestine, are likely precancerous. Serrated adenomas are a particularly aggressive form of adenoma.
Some polyps are the result of hereditary conditions, such as familial adenomatous polyposis (Tumors of the Digestive System: 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.
Symptoms and Diagnosis
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 (villous adenomas) may excrete water and salts, causing profuse 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 performed to examine the entire large intestine. This complete and reliable examination is performed because more than one polyp is usually present and any may be cancerous. Colonoscopy also allows a doctor to perform 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, 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.
When a person has a polyp removed, the entire large intestine and rectum are examined by colonoscopy once a year for 2 years and then at intervals determined by the doctor. If such an examination is impossible because of a narrowing of the large intestine, a barium enema may be used to view the large intestine on x-ray.
Last full review/revision February 2013 by Elliot M. Livstone, MD