Management of Colonic Polyps and Adenomas
Polyps of the colon are mucosal lesions which project into the lumen of the bowel. According to autopsy studies, colonic polyps occur in more than 30% of people over the age of 60. Approximately 70-80% of resected polyps are adenomatous. Adenomatous lesions have a well-documented relationship to colorectal cancer. This adenoma-carcinoma progression represents a significant public health problem, since colorectal cancer is the second leading cause of cancerspecific mortality in the United States. Therefore, appropriate management of colonic polyps may reduce the risk of death from colorectal cancer.
Types of Polyps
There are four types of colonic polyps: adenomatous, hyperplastic, harmartomatous and inflammatory. In addition to these histologic features, polyps are generally described as being either sessile (flat) or pedunculated (having a stalk). Inflammatory and small hyperplastic polyps do not have malignant potential and therefore do not require any further intervention and should not alter surveillance intervals. While most harmotomatous polyps do not have malignant potential, those associated with Peutz-Jeghers syndrome and juvenile polyposis do contain a risk for malignant transformation and therefore require more aggressive intervention and monitoring. Adenomatous polyps are considered precursors for invasive colon and rectal cancer. Histologically these polyps are either villous, tubular or tubulovillous. The risk of malignancy increases with both the size of the polyp and the degree of villous component.
Most colonic polyps are asymptomatic. Those which are symptomatic usually present with lower GI bleeding. This may range from occult bleeding, as detected by fecal occult testing or the presence of iron deficiency anemia, to frank blood per rectum. Polyps are rarely the source of a significant lower GI bleeding. Some low rectal polyps may cause a mucus discharge from the rectum. Most polyps cannot be discovered by physical exam. However, some low-lying rectal polyps can be detected by digital rectal examination.
There are asymptomatic patients who are at high risk. These include patients with a family history of polyps or colon and rectal cancer, patients with ulcerative colitis or Crohn’s disease, and patients with a polyposis syndrome (i.e., familial adenomatous polyposis, hereditary nonpolyposis colorectal cancer [HNPCC]).
Methods of Diagnosis
There are several methods available to detect colonic polyps. These include: fecal occult blood testing, sigmoidoscopy, colonoscopy and the combination of barium enema and sigmoidoscopy. Fecal occult testing is a simple, non-invasive test done by most primary care physicians. There are several studies suggesting that yearly fecal occult testing, especially if combined with sigmoidoscopy, may decrease the mortality of colorectal cancer. Proper follow up testing, usually colonoscopy, is mandatory for patients with positive results. Colonoscopy is now accepted as the most accurate method of detecting colonic polyps. Colonoscopy also allows simultaneous removal of most lesions.
However, colonoscopy is clearly the most invasive and the most expensive of our screening tools. Nevertheless, colonoscopy is rapidly becoming the most common method for colon polyp and cancer screening. Current recommendations for non-high risk patients (i.e., no family history) is to begin surveillance at age fifty with routine colonoscopy. Since most clinically significant colon polyps are located distal to the splenic flexure, flexible sigmoidoscopy may be a reasonable alternative to colonoscopy.
However, lesions in the right colon may go undetected and those patients found to have a polyp on flexible sigmoidoscopy will then need a full colonoscopy, subjecting these patients to both tests. The combination of double contrast barium enema and sigmoidoscopy is better tolerated by some patients and is less expensive and safer than routine diagnostic colonoscopy, but obligates many patients to a second procedure for therapeutic intervention. The incidence of significant bleeding and perforation is less than 1% for colonoscopy, as compared to only 0.01% for the barium enema. Virtual colonoscopy, while seemingly effective at detecting polyps, is still not considered ready for routine clinical use. Genetic testing of stool may also be able to non-invasively detect polyps and colon cancers, but still needs considerable development before it can be used in routine clinical practice.
Management of Colonic Polyps
Patients undergoing treatment of colonic polyps require mechanical bowel preparation prior to colonoscopy. Most polyps can be removed during colonoscopy using electrocautery techniques. Surgical removal is indicated only when an experienced endoscopist cannot completely remove the polyp safely. In order to minimize the risk of future malignancy, polyps should be completely removed or destroyed. While total excision of the polyp is desirable, small polyps (0.5 cm or less) can be treated by biopsy and fulguration. Most pedunculated polyps are amenable to snare polypectomy using electrocautery.
Sessile polyps larger than 2 cm usually contain villous features, have a higher malignant potential, and tend to recur following colonoscopic polypectomy. If complete or safe colonoscopic resection is not possible for technical reasons, the lesion should be biopsied and the patient referred for primary surgical therapy. In cases where the lesion can be removed via the colonoscope, follow-up endoscopy should be done in 3-6 months to confirm complete resection. Residual adenomatous tissue noted at follow-up colonoscopy should be removed and another confirmatory colonoscopy performed 3 months later. Surgical resection is recommended for residual abnormal tissue at the polypectomy site after two or three attempts at colonoscopic removal.
The resected polyp must be completely examined pathologically. Histologically, adenomatous polyps can show a benign adenoma (tubular, tubulovillous or villous), carcinoma in situ, or invasive cancer. Colonoscopic removal is definitive therapy for benign adenomatous polyps or inpatients having polyps with carcinoma in situ. If pedunculated polyps contain invasive carcinoma, colonoscopic removal is adequate treatment in the uniform presence of favorable prognostic indicators such as complete excision, no lymphovascular invasion, clear margins, and well-differentiated histology. A follow-up examination within three months is mandatory to confirm the presence or absence of residual or recurrent disease. Any patient with lesions not meeting these criteria should undergo elective resection of the involved segment of the colon or rectum. Additional staging procedures such CT scanning, endoscopic ultrasound, or endorectal MR may be helpful.Post-Polypectomy Surveillance
The entire colon must be examined during the polypectomy so that
any synchronous lesions can be detected and removed. Approximately 50% of
patients will have a second adenomatous polyp at the time of initial
colonoscopy, while metachronous polyps are found in 20-50% of patients within
five years of the initial polypectomy. If follow-up colonoscopy verifies that no
residual polyps exist, colonoscopy should be repeated within three years and
thereafter every five years. Patients who undergo complete removal of a solitary
tubular adenoma smaller than 1 cm should have a surveillance colonoscopy five
years post polypectomy. However, even longer intervals have been suggested. In
the future new evidence may indicate the interval in these patients.
Complications of Colonoscopic Polypectomy
Colonoscopic polypectomy has an overall complication rate of 1-2%,
with bleeding as the most common complication. Other complications include free
perforation of the bowel, microperforation, transmural electrocautery burn,
pneumatosis cystoides intestinalis, splenic capsular tear, and avulsion of a
mesenteric blood vessel. Many of these complications can be treated as
necessary, but peritonitis or unrelenting hemorrhage requires urgent laparotomy.
Surgical Treatment of Colonic Polyps
A colonic polyp that is deemed unresectable endoscopically requires a colonic resection. Localization is critical prior to surgical removal. Lesions can be endoscopically tattooed prior to surgery to assist in localization. Introperative colonoscopy may also be necessary if the lesion is not readily identifiable. The specimen should be opened at the time of surgery to confirm resection of the suspicious lesion. Since surgery is reserved only for those polyps deemed endscopically unresectable, these polyps must be considered high risk for containing an invasive malignancy. Therefore, surgery, whether laparoscopic or open, should follow the principles of colorectal cancer surgery.
Effective surgical treatment of rectal polyps would require full thickness excision for lesions of moderate size to an extensive mucosectomy for larger lesions. Such techniques may save patients the significant morbidity of having a proctectomy. For patients with endscopically unresectable polyps of the upper rectum, transanal endoscopic microsurgery (TEM) may be an option, but requires specialized expertise.Qualifications for a Surgeon Treating Colonic Polyps
The qualifications of a surgeon performing any operative procedure
should be based on training (education), experience, and outcomes. At a minimum,
surgeons who are certified or eligible for certification by the American Board
of Surgery or the Royal College of Physicians and Surgeons of Canada, or their
equivalent should perform colonoscopy and/or colectomy. These surgeons have
successfully completed at least 5 years of surgical training after medical
school graduation and are qualified to perform operations on the colon. The
level of training in advanced laparoscopic techniques necessary to conduct
minimally invasive surgery of the colon is important to assess.
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DeMeester, S and Choti, MA. “Colorectal Polyps” in Current Surgical Therapy. Cameron, JL, ed. 7th edit, pg255, 2001.
Tomlinson I, Ilyas M, Johnson V, et al A comparison of the genetic pathways involved in the pathogenesis of three types of colorectal cancer. J Pathol 184: 148, 1998.
Key Words - patient, guideline, colorectal, colonic, polyps, surveillance, polypectomy, colectomy, neoplasia, colonoscopy, adenoma.