Colonic polyps are growths of the colonic (large intestine) or rectal (lower segment of
large intestine) mucosa (thin lining of bowel).
Although most colorectal polyps are harmless, some polyps called adenomas have the
potential to become malignant (cancerous). Therefore, adenomatous polyps need to be
removed and the patient needs to be followed with screening colonoscopy.
Most polyps are isolated findings on screening colonoscopy, but some occur as part of
inherited cancer syndromes and are more numerous, carrying a much higher risk for
colorectal carcinoma.
Colonic polyps are very common being detected in 30-50% of the adult population. Only
10% of the colonic polyps are adenomatous.
Men and women are equally affected, and polyps are associated with increasing age being
more commonly detected after 50 years of age. Therefore, the first screening colonoscopy
should be performed at this age.
The size of the polyp is directly associated with the risk for malignant transformation.
Scientific studies showed that the risk for cancer development from isolated polyps of 1
cm (approximately half and inch) is 8% at 10 years and 24% at 20 years.
Several causes for colorectal polyps have been hypothesized but the responsible factor
remains unknown. Dietary and environmental factors (high-fat diet, low-fiber diet,
smoking, obesity) have been incriminated as possible causes, along with hereditary
factors.
Recent studies showed that aspirin, folic acid and calcium intake reduce the number of
polyps and appear to protect against the development of colorectal carcinoma.
Several cancer syndromes such as Familial Adenomatous Polyposis and Peutz-Jeghers syndrome
are characterized by the presence of hundreds to thousands of polyps that are the direct
result of specific genetic mutations that are passed on to several generations. These
polyps have a much higher risk for malignant transformation at an earlier age, and
generally require removal of the entire colon (colectomy) in order to prevent the
development of the cancer.
Most of the polyps are small and do not produce any symptoms or signs. The larger
polyps may twist or may become traumatized by the fecal stream, and therefore may bleed
causing either a black stool or red blood streaks on normally colored stool.
Other symptoms may include constipation, diarrhea, abdominal pain and obstruction if the
polyp is very large.
There is no laboratory (blood) test that can diagnose colorectal polyps.
The most commonly employed diagnostic methods include fecal occult blood test (chemical
detection of trace amounts of blood in stool), digital rectal exam (identifies low-lying
rectal polyps or tumors), barium enema (detects large polyps) and direct visualization of
colonic lining by flexible sigmoidoscopy and colonoscopy.
Colonoscopy is the most sensitive diagnostic method for colorectal polyps and cancer.
During the colonoscopy, a thin flexible tube (colonoscope) is inserted through anus and
passed through the entire colon. The colonoscope is equipped with a small video camera
that captures images from the entire colonic lining. The images are transmitted real-time
to a video monitor allowing the doctor to detect any mucosal lesions. At the time of
colonoscopy small tissue samples from various lesions can be taken and submitted to the
pathology laboratory for microscopic examination. If small polyps are identified, they can
be entirely removed during colonoscopy.
A colonoscopy usually takes about half an hour and is performed under mild anesthesia
(conscious sedation). The complications are uncommon and may include bleeding and colonic
perforation.
If numerous polyps are identified at colonoscopy, the possibility of a hereditary cancer
syndrome should be considered. Additional genetic testing may be necessary for diagnostic
purposes.
The most common complication is rectal bleeding or occult bleeding that may result in
iron deficient anemia.
Intestinal obstruction may occur with large pedunculated polyps, and may present with
abdominal pain, nausea, vomiting and constipation.
The most ominous complication of adenoma is the malignant transformation to
adenocarcinoma.
To prevent the development of colorectal carcinoma, screening colonoscopy is recommended
for the general population starting at 50 years of age. The patients with adenomatous
polyps detected at first colonoscopy as well as their first-degree relatives (parents,
brother, sister, and child) are at increased risk for developing additional polyps or
cancer. Thus, it is important that the patient and the immediate family members have
follow-up colonoscopies and, in certain cases, additional genetic consultation.
All polyps should be completely removed at the time of colonoscopy. Some large polyps
cannot be entirely removed endoscopically. Thus, depending on the type of the polyp,
surgical resection of the segment of colon containing the polyp may be needed. This may be
accomplished using laparoscopic techniques. During this procedure, the surgeon makes small
incisions in the abdominal wall, and using small surgical instruments with attached video
cameras, can adequately remove the segment of the colon containing the polyp. The recovery
is faster and less painful than the recovery from traditional open surgery.
The patients with hereditary polyposis syndromes usually require more extensive surgery
consisting of removing the entire colon and rectum (proctocolectomy) with the creation of
a ileal reservoir (a segment of small bowel that is sutured to the anus, thus preserving
the rectal function).
Nutrition and lifestyle changes may reduce the risk of colorectal polyps and carcinoma.
Guidelines issued by American Gastroenterological Association recommend the following:
- Reducing fat intake, especially saturated fat found in animal sources (red meat,
whole mil, cheese, ice cream) or in coconut and palm oils.
- Increasing fruit, vegetable and whole grain intake.
- Stop smoking and reduce the alcohol intake.
- Increasing the amount of calcium and folic acid in the diet.
Medical treatment with aspirin (325mg a day) or other non-steroidal antiinflammatory
drugs (NSAIDs) may be effective in reducing the risk of colorectal polyps and carcinoma.
Mayo
Clinic Foundation
National Digestive Diseases
Cleveland
Clinic
