Scot M. Lewey, DO, FACG, FASGE, AGAF
Clinical Professor of Medicine
Colon polyps are benign (not cancer, but potentially pre-cancerous) neoplasms (new growths) in the colon. The come from cells in the colon lining that make too many copies of themselves, clones of cells, that result in a growth that projects off the surface lining of the bowel. Some are flat (sessile), some grow a head like shape that pulls away from the lining on a stalk (pedunculated) and some are more mound like (mountain shaped polyps). Almost all colon cancers come from large colon polyps, that start out as small polyps.
Polyps can be seen in the colon directly during scope examination of the large intestine (colonoscopy, sigmoidoscopy) or may be seen as projections during imaging procedures such as barium enema and "virtual colonoscopy". Virtual colonoscopy is only virtual in the sense that images from a combined barium enema and CT scan are reconstructed by a computer program to produce a virtual exam that a radiologist views as if you were having a colonoscopy, this is properly known as "CT colonography". Both barium enema and CT colonography require a bowel preparation or "clean out" as does a colonoscopy exam. Sedation is given for a colonoscopy but not for the imaging studies. Polyps found on the imaging studies cannot be removed at the time of the exam whereas in colonoscopy the polyp is both seen and removed, unless too large.
Below are images of actual colon polyps both with standard light imaging and something called "narrow band imaging" or NBI that utilizes a different light wave to help see features of polyps or other tissue more clearly including those that indicate the tissue may be pre-cancerous or cancer.
The images above are of the same polyp. On the left this "mountain type" polyp is seen with normal light wave colonoscopy. On the right the polyp is seen under Narrow Band Imaging (NBI) light wave. This often helps delineate normal colon lining from pre-cancer or cancerous tissue.
The colon polyp in previous images is ensnared to be removed. .
The polyp above (seen in NBI view) is in process of being grasped by a hot biopsy for polypectomy (polyp removal).
The two images above depict the two tradtitional polypectomy (polyp removal) techniques. On the left the polyp is removed with a electrical wire snare technique. On the right the polyp is being cauterized and removed using hot biopsy polypectomy technique.
Sessile type polyp under standard light exam.
The sessile polyp under Narrow Band Imaging (NBI) light wave exam showing more details of the surface typical of a pre-cancer type polyp.
Sessile polyps are relatively flat broad polyps. The may require removal in in pieces ("piecemeal technique"). The NBI light wave view on right helps delineate the polyp more distinctly from surrounding normal colon lining as well as shows features of "pre-cancer" adenomatous type polyps.
Sessile polyp slightly raised easily missed (was missed by previous doctor who performed colonoscopy on this patient)
Narrow Band Imaging (NBI) brings out the features of this sessile polyp including contrast from normal tissue and "pre-cancer" adenomatous appearance.
Some flat or sessile polyps are difficult to see but NBI helps define these pre-cancerous polyps better. Removal of this broad relatively flat polyp required a "piecemeal" technique where the polypectomy snare wire is used to grasp pieces to "carve" them off with cautery.
A oblong or kidney bean shaped sessile polyp on a fold in the colon.
NBI view of the polyp showing "pre-cancer adenomatous features and delineating the margins of the polyp and normal tissue.
Polyps often are found on the edges of folds of the lining of the colon lining. Sometimes "bumpiness" of the folds can mimic polyps. Narrow band imaging can help confirm that the "bump" is a true polyp that needs to be removed.
Another view of the sessile polyp on a fold edge.
Biopsy slide of a classic "tubular adenoma" polyp that are "pre-cancer" but not cancer.
Adenomatous "pre-cancer" type polyp have typical features both visually during colonoscopy and "histologically", that is under the microscope.
These two photos show variations of sessile ("flat") polyps. The one on the left is moderately large, broad and multilobulated though still relatively flat in the cecum of the colon. The polyp on the right is very small, located on a fold but also relatively flat found in the ascending colon. The larger sessile polyp required piecemeal excision with a snare, the smaller polyp was removed by hot biopsy polypectomy technique. Both polyps are seen much better with the Narrow Band Imaging technique that helps distinguish true polyps from surrounding normal colon lining tissue.
Semipedunculated polyp in rectum. The red is minor bleeding from irritation of the polyp surface from the colonoscope.
The same semipedunculated polyp in rectum seen inthe NBI view. Under this light wave image view the blood appears black like ink.
Though this polyp is not particularly large, it is easy to see how it may cause blood in the stool. The blood, if less than a teaspoonful, may not discolor the stool but can be detected by fecal occult blood tests of the stool. These tests can be helpful for detecting polyps and/or colon cancer because of their propensity to result in blood in the stool. However, waiting until blood is seen in the stool or detected with the stool tests can be too late. It is better to have a colonoscopy and have all polyps detected and removed before they become advanced cancer. The images below show how this polyp is ensnared, removed and no residual polyp tissue is left.
These two images are a sequence of the polyp being ensnared before cautery snare removal (snare polypectomy) and after removal where only a cauterized base remains. All polyp pre-cancer tissue has been removed and any residual pre-cancer cells would be destroyed by the cautery. The area will heal over 10-14 days. Sometimes the polyp cautery area will bleed from the ulcer that occurs during the healing stage. The risk of post-polypectomy bleed is increased if the patient takes aspirin or NSAIDs (e.g. ibuprofen, motrin, advil, aleve etc.), antiplatelet (e.g. plavix) or anticoagulant medications (e.g coumadin/warfarin), or if the patient has high blood pressure, a very large polyp or a polyp with a vessel in the stalk..
This rectal polyp is moderately small but large and raised enough that it could be removed by snare. The polyp is gathered up by snare and removed by snare cautery.
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