Description, Causes and Risk Factors:
Polyp: A general descriptive term used with reference to any mass of tissue that bulges or projects outward or upward from the normal surface level, thereby being macroscopically visible as a hemispheroidal, spheroidal, or irregular moundlike structure growing from a relatively broad base or a slender stalk; polyps may be neoplasms, foci of inflammation, degenerative lesions, or malformations.
Sessile polyp: Any form of polyp that has a relatively broad base.
Types may include: Sessile polyp in deuodnum, sessile polyp in colon, sessile polyp in stomach, sessile polyp in sigmoid colon, sessile polyp in transverese colon, sessile polyp in gastric colon, sessile polyp in hepatic flexure, sessile polyp in hepatic flexure, sessile polyp in uterus, sessile polyp in uterus.
Sessile polyps simply mean that the mass is flat and does not have a stalk. The other types of colonic polyps are pedunculated- these are not flat but attached to a stalk. Since a sessile colonic polyp does not have a stalk, it is usually found very close to the colonic wall lining. Other than this structural difference there are no other physiological or biochemical differences between these two types of polyps. The majority of sessile growths are asymptomatic and only rarely do these polyps become cancerous. Colonic polyps can vary in size from a few mm to a few cms. The exact incidence of colonic polyps is not known but autopsy data indicate that anywhere from 7-50 percent of individuals have these growths. Polyps are usually multiple and are most commonly found in the left colon and rectum. Multiple colonic polyps are very common in individuals with polyposis syndromes like Gardner's, Turcot's and familial polyposis coli.
A sessile polyp in colon occurs when cells of the innermost layer begin to divide rapidly and grow. These cells normally divide faster that the rest of the cells in the body since they form a layer called an epithelia. An epithelial layer is one that exists to protect the inside workings of the body from the outside. Even though the colon lies within the abdomen, the stool and all of the material that a person eats is treated as though it is outside the body. Therefore the epithelia have to provide a barrier function against these elements. Because epithelia are constantly exposed to toxins and other agents, they need to be replaced on a regular basis in order to maintain the integrity of the layer. Other tissues are not replaced like this. For example, neurons of the brain do not divide and replace each other, neither do the kidney are heart cells. Only the cells of the skin, GI tract and blood are constantly turning over to make new copies.
In the process of constantly creating new copies of the cells, some errors can be made in the DNA. The mechanism of copying the DNA is not always perfect. So when the layers of the colon are replicated, it is possible for a mutation to occur. As the mutations buildup and expands, it can form a sessile polyp colon. There are other ways of developing mutations. Some times people have genetic issues in their family that increase the rest of mutations. Other times a person can have been exposed to radiation or chemotherapy. These agents have devastating effects on the replication of cells and cause them to develop a lot of different mutations.
Polyps usually cause no symptoms until they grow to 2cm or more in diameter. While most polyps have no symptoms, some may present with blood in the rectum. The bleeding may be seen on tissue paper or on the stools. When the polyps are large, one may develop abdominal cramps, pain, constipation or diarrhea.
Because most polyps have no symptoms, it is recommended that one undergo some type of a screening test after the age of 50. The best test to detect polyps is colonoscopy. This involves completely cleaning the bowel for 24-48 hours with clear fluids and an enema and then looking up the rectum and colon with a flexible colonoscope. Colonoscopy is the best test as one can visualize the entire colon and any polyp seen can be removed. Other tests to look inside the colon include barium enema and video capsule endoscopy. Barium enema is not very sensitive for polyps less than 1 cm and one is not able to biopsy the lesion. Video capsule endoscopy is a novel technique and like barium enema, it is not possible to biopsy the lesion. The role of video capsule endoscopy as a screening test is still being debated.
Polyps can be seen directly during colonoscopy (telescope examination of the whole large bowel starting at the rectum). An experienced doctor can often differentiate metaplastic polyps from the pre-malignant adenomatous polyp by appearance alone.
Nevertheless, most doctors prefer not to take the risk of getting it wrong and either take biopsy samples (small bites of tissue) or cut out the entire polyp (polypectomy). In this case, checking the polyp's cells under the microscope (histology) is not essential providing that the doctor is certain that the polyp has been completely removed.
Symptomless polyps are often found at barium enema examination (an X-ray test done after barium liquid is poured into the rectum) in a patient with bowel symptoms that could be due to irritable bowel syndrome. They are also commonly found by chance when screening is performed using flexible sigmoidoscopy (examination of the lowest part of the bowel using a bendy telescope) or colonoscopy.
Endoscopic mucosal resection (EMR) has become the standard technique for resection of large sessile and flat colorectal lesions. Its simplicity is the key. By working with the natural tissue planes of the colonic wall, surprisingly large lesions can be removed without the need for heavy sedation or inpatient stay. The submucosa is composed of loose areolar tissue which can be filled with fluid, “ballooning” the mucosa away from the underlying muscularis propria and making polypectomy inherently safer and easier.
The term EMR encompasses several techniques, from simple saline injection for snaring a small sessile polyp through to widespread piecemeal excision of hemicircumferential 10-cm lesions. Good EMR technique ensures high levels of safety and complete endoscopic excision, offering a powerful tool for cancer prevention. It represents a major step towards the evolution of “colonoscopic surgery”, the ultimate form of minimally invasive surgery - an operation from within.
Basic EMR technique for sessile polyps 1-2 cm in size, or for small flat adenomas smaller than 1 cm, should be within the armamentarium of all colonoscopists. However, effective endoscopic removal of large or complex lesions by EMR can only be achieved by appropriate referral to expert endoscopists skilled in the technique, and all too often patients with lesions that could be removed endoscopically undergo surgery because there is a lack of an appropriate referral pathway. Surgery carries a greater immediate patient risk and invariably results in a loss of intestinal length and function. Conversely, the use of poor endoscopic technique by inexperienced endoscopists may be equally harmful, risking incomplete removal or major endoscopic complication. An excellent way of learning both basic and advanced EMR techniques is by means of the various animal models which have gained widespread approval and should be part of all training programmes.
Approximately 3%-6% of colorectal adenomas detected at colonoscopy are large sessile polyps and up to 20% of all polyps are flat or minimally elevated. The detection of these lesions is likely to increase with the introduction of population screening for colorectal cancer (CRC). Thus a significant number of lesions are potentially suitable for removal by either basic EMR at routine colonoscopy or by piecemeal excision by an expert colonoscopist at a specialist clinic.
Complications include bleeding and perforation.
Large, rectal polyps can sometimes be removed through the anus under general anaesthetic without the need to cut open the abdomen.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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