Pearls and Pitfalls in Polypectomy

Douglas K. Rex, MD

 


Keywords

Pedunculated polyps, polypectomy, sessile polyps.


Introduction

Colonoscopic polypectomy has been shown in three studies to prevent about 80% of incident colorectal cancers (1-3). Despite this, the actual performance of polypectomy is only partly science and mostly an art form that has developed over 30 years of anecdotal reporting of polypectomy practices. If one were to judge the level of evidence supporting individual polypectomy techniques currently practiced, none of it would be "Level A" evidence. Given these limitations, this paper is an unapologetic commentary on pearls and pitfalls in polypectomy, based solely on the practices and writings of previous experts in colonoscopy and on the author’s own experience. This paper is not comprehensive in its review of polypectomy technique, but rather focuses selectively on issues that the author finds to often be a source of error or that the author perceives might be better or more safely performed in general practice.

Small Polyp Removal

Video Clip 1: Cold snare resection of a small sessile polyp is shown. Note that a rim of normal tissue around the polyp can be taken to reduce the risk of recurrence.

The overwhelming majority of colorectal polyps are less than 1 cm in size and the great majority of such polyps will never harm anyone by development into cancer, bleeding, or other symptoms. There is certainly a strong rationale to remove all polyps from the colon in patients with a substantial life expectancy, if for no other reason that it would be too costly to observe them. The author strongly recommends the use of cold snare removal for most sessile polyps < 6-7 mm in size (4). The use of hot forceps is inappropriate for any polyp larger than 5 mm but even for polyps <5 mm, neither hot forceps or cold forceps effectively removes the entire polyp (5). Cold snaring has the advantage of effective removal, though a large study would be needed to determine if it is as effective as hot snaring. Cold snaring has the distinct advantage of eliminating cautery-related complications. The use of electrocautery is the cause of polypectomy-related perforations and it may result in delayed bleeding by injury of submucosal arteries. One concern often expressed about cold snaring is that the polyp may be difficult to retrieve. In fact, the polyp almost always remains in place near the polypectomy site (Video Clip 1) and can be readily suctioned into a trap. In our unit, we retrieve > 95% of polyps removed by cold snaring. If an occasional polyp is lost, it is extremely unlikely to have any significance. A second concern is often that of immediate bleeding. However, small polyps have small vessels and the bleeding that occurs after cold resection of small polyps is capillary bleeding which will invariably stop on its own. The colonoscopist can safely ignore it, unless there is impressive and continued steady streaming from the polypectomy site. In the author’s experience, this happens only occasionally in an anticoagulated patient or a patient with significant liver dysfunction. Thus, in only a rare instance is it necessary to cauterize the site using multipolar cautery or to clip it closed.

The Patient Who Is Anticoagulated or on Antiplatelet Agents

The American Society for Gastrointestinal Endoscopy recommends that no provisions be taken for polypectomy in patients on aspirin (6). In clinical practice, most gastroenterologists, including myself, do make some provision for aspirin use. In patients taking aspirin for primary prophylaxis (often self-prescribed), we typically instruct them to stop aspirin a week to ten days before the procedure and may keep patients off aspirin for up to two weeks after the procedure if electrocautery was used. If patients arrive in the endoscopy unit having taken aspirin despite our instructions, we proceed with their colonoscopy and remove polyps, whatever the size. If there is not a strong indication for aspirin use, however, we ask the patient to remain off of aspirin for two weeks after the procedure, if electrocautery was used. If patients are on aspirin with strong indications for prevention of cardiovascular or neurologic events, we do not discontinue the aspirin. My own rationale for the approach described above is that aspirin and NSAIDS make all lesions in the GI tract more likely to bleed, and there is no reason why this should not apply to polypectomy burns. However, the absolute risk of bleeding from polypectomy burns, in patients on aspirin only, is very low.
Experience in out unit with patients taking both aspirin and clopidogrel (Plavix) has been that this combination is associated with a high risk of bleeding. Considerable caution should be taken in performing therapeutic procedures on patients taking both aspirin and clopidogrel, including polypectomy with electrocautery. We commonly ask patients to discontinue clopidogrel for five days prior to polypectomy and for a variable period of time afterwards, depending on the size of the lesion and the patient’s cardiovascular risk.

Video Clip 2: A polypectomy scar is shown in a patient who is to be re-anticoagulated. The site is closed by placement of two metal clips.

For patients on warfarin who are low risk for a thromboembolism (atrial fibrillation without left atrial dilation, deep venous thrombosis after six months of therapy), it is acceptable to discontinue warfarin 3 to 5 days prior to colonoscopy and to resume it following the colonoscopy or after some delay if there appears to be a substantial risk of bleeding. For patients at high risk (e.g. atrial fibrillation with mitral valve disease and left atrial dilation, prosthetic mitral valves), it is usually acceptable to discontinue warfarin and continue Lovenox as an outpatient, giving the last dose 24 hours prior to the procedure. Both Lovenox and warfarin can then be restarted on the evening of the procedure. We often perform colonoscopy in high-risk patients while they continue on anticoagulation and remove the small polyps using cold forceps or cold snare. In some instances, we remove slightly larger polyps with electrocautery and place a clip over the site; anecdotally, this practice has been successful. [However, the ASGE recommends that for polypectomy, anticoagulation should be reversed (6).] Since most patients undergoing colonoscopy have either normal colons or only small polyps, the approach described above of trying the procedure while the patient is anticoagulated probably results in cost savings. If a larger polyp for which electrocautery is needed is identified, the patient can be scheduled for a repeat colonoscopy on another day, the warfarin discontinued, and the patient placed on Lovenox. Although Lovenox is less expensive than hospitalization and heparinization, the safety of Lovenox in high-risk patients has not been established by prospective trials. Certainly discontinuation of warfarin, followed by hospitalization and intravenous heparinization after the INR has drifted down, is an alternative. In this case, intravenous heparin is discontinued four hours prior to the colonoscopy and restarted 4 to 6 hours afterwards. Whenever patients are to be re-anticoagulated, consideration should be given to clipping the polypectomy site closed, if feasible (Video Clip 2). Prospective studies of the effectiveness of this practice are needed.

 

Large Pedunculated Polyps

Video Clip 3: A polypectomy stalk in a patient to be re-anticoagulated is lassoed with Endoloop. Endoloop can also be placed prior to snare cautery resection of pedunculated polyps.

Experienced colonoscopists should be able to remove essentially any mucosally-based pedunculated polyp, regardless of size. Endoloop, or the detachable snare, is effective in preventing bleeding in one small randomized trial (7), and its use should be considered an option (Video Clip 3). Truly huge pedunculated polyps occasionally require piecemeal resection of the head, in order to pair it down a size that allows getting the snare around the base. In this instance, it is best to send the base as a separate pathologic specimen, since if cancer is present, it is most important to know if it is in the section adjacent to the polyp stalk. Rotating the patient can facilitate snaring the very large polyp, by changing its position as it moves with gravity.

 

Access Problems

Areas where access problems occur commonly are on the medial wall of the cecum, just proximal to the ileocecal valve, and on the proximal sides of folds, flexures, and turns. Large sessile polyps located on the proximal side of sharp sigmoid bends can be problematic. The easiest solution is to remove the polyp in retroflexion. In the left colon, this can be accomplished using an upper endoscope that is evaluated before insertion to ensure that it has maxium tip deflection. For the polyps in the proximal colon, a pediatric colonoscope can be useful. The author has tested a prototype Olympus pediatric variable stiffness colonoscope with a short bending section, which has a very tight turning radius and allows retroflexion anywhere in the colon, including in the cecum (8) (Figures 1A-1F).

 

Figure 1A
Figure 1B
Figure 1C
     
Figure 1D
Figure 1E
Figure 1F


The Very Flat Polyp

Occasional very flat polyps can be impossible to snare and the problem persists after submucosal saline injection. In the rectum and sigmoid, the best solution is the EMRC cap (9). In the proximal colon, such polyps can be treated by biopsy, followed by ablation, or one can try a snare designed to dig into the mucosa such as the Olympus barbed snare.

 

The Large Sessile Polyp

Video Clip 4:
A large sessile polyp involving about 50% of the rectum is removed. (See caption on larger versions for additional information.)

The usual guidelines for endoscopic resectability of a large sessile polyp are that the lesion should occupy no more than 30% of the circumference of the colon and not extend across two haustral folds. These are only guidelines and experts often remove larger polyps if they appear to be readily accessible. The most important determinate of accessibility is usually the section of the colon that the polyp is in. Thus, in the large caliber right colon, transverse, or rectum, polyps that occupy 50% or even more of the circumference may be resectable. The main difficulty with polyps extending across two haustral folds is the section that dips down between the haustral folds. This area can be very difficult to access.

For submucosal saline injection, it can be useful to add a few drops of methylene blue to about 60cc of normal saline or D50. D50 stays in place and maintains the submucosal cushion longer than saline (10). The goal should be to resect all of the polyp on the first attempt, regardless of size, and to ablate any residual flat disease that cannot be resected, all in the first attempt (Video 4). Resection is preferable to ablation, though most large sessile polyps have at least some small section of extremely flat disease that must be ablated or removed using the EMR cap. No randomized trials have compared ablation tools but most experts currently favor the argon plasma coagulator (Video Clip 4) (11). It allows a controlled cautery burn in a non-contact fashion. Power settings should be 40 watts in the cecum, up to 45 watts in the right and transverse colon, and can increase progressively in the distal colon, and as much as 60 to 65 watts in the distal rectum.



Correct Pathological Interpretation

Sometimes serious mistakes are made in the management of endoscopically resected polyps based on their pathologic interpretation. The most serious errors follow the use of the terms, "carcinoma in-situ" or "intramucosal adenocarcinoma" (12) (Figures 2A- 2D). Neither of these pathologic entities constitutes colorectal cancer and both are associated with a zero risk of metastasis. Therefore, if a polyp has been endoscopically resected in patients with such pathologic readings, the patient should be considered cured. In order to avoid confusion, it is best for the pathologist not use these terms but rather refer to both entities as "high grade dysplasia." If invasive cancer is present, the pathologist must designate the proximity of the cancer to the endoscopic resection line, the degree of differentiation, and whether the lymphatic (vascular) invasion is present. Various studies have used different minimum margins (1, 2, or 3 mm) as acceptable. At a minimum, the cancer should not abut the resection line or surgical resection should be recommended.

Figure 2A
Figure 2B
Figure 2C
Figure 2D

 


Follow-Up of Large Polyps

Large pedunculated polyps with high-grade dysplasia, provided the endoscopist is sure there has been complete resection, can undergo their first follow-up in three years. If adenocarcinoma is detected in the polyp and histologic criteria are favorable and a decision is made to not perform surgery, some have advised a re-inspection of the polypectomy site and biopsy in three months. Although the value of this practice is questionable, there is no clear data to prove that it has no value.

Large sessile polyps removed in piecemeal fashion should be followed closely to ensure complete resection, regardless if the dysplasia is low-grade or high-grade. I typically recheck the site in three months, though some people wait as long as six months. If the polypectomy site appears free of polyp, there is a rationale to perform yet another reexamination in one year. This is because of so-called "late recurrences," which may account for up to half of all recurrences after removal of large sessile polyps (13). In my own anecdotal experience, biopsy of the polypectomy scar at three months effectively predicts which patients will subsequently develop a recurrence of overt polyp. If dysplastic tissue is present in the polypectomy base, this predicts the subsequent recurrence of an overt polyp.

 

REFERENCES

1. Winawer SJ, Zauber AG, Ho MN, et al. Prevention of colorectal cancer by colonoscopic polypectomy. The National Polyp Study Workgroup. N Engl J Med 1993;329:1977-81.

2. Jorgensen OD, Kronborg O, Fenger C. The Funen adenoma follow-up study: Incidence and death from colorectal carcinoma in an adenoma surveillance program. Scand J Gastroenterol 1993;28:869-74.

3. Citarda F, Tomaselli G, Capocaccia R, et al. Efficacy in standard clinical practice of colonoscopic polypectomy in reducing colorectal cancer incidence. Gut 2001;48:812-5.

4. Tappero G, Gaia E, DeGiuli P, et al. Cold snare excision of small colorectal polyps. Gastrointest Endosc 1992;38:310-3.

5. Peluso F, Goldner R. Follow-up of hot biopsy forceps treatment of diminutive colon polyps. Gastrointest Endosc 1991;37:604-6.

6. ASGE. Guideline on the management of anticoagulation and antiplatelet therapy for endoscopic procedures. Gastrointest Endosc 1998;48:672-5.

7. Iishi H, Tatsuta M, Narahara H, et al. Endoscopic resection of large pedunculated colorectal polyps using a detachable snare. Gastrointest Endosc 1996;44:594-7.

8. Rex DK. Accessing proximal aspects of folds and flexures during colonoscopy: impact of a pediatric colonoscope with a short bending section. Am J Gastroenterol (in press).

9. Tada M, inoue H, Yabata E, et al. Colonic mucosal resection using a transparent cap-fitted endoscope. Gastrointest Endosc 1996;44:63-5.

10. Conio M, Rajan E, Sorbi D, et al. Comparative performance in the porcine esophagus of different solutions used for submucosal injection. Gastrointest Endosc 2002;56:513-6.

11. Zlatanic J, Waye JD, Kim PS, Baiocco PJ, Gleim GW. Large sessile colonic adenomas: use of argon plasma coagulator to supplement piecemeal snare polypectomy. Gastrointest Endosc 1999;49:731-5.

12. Rex DK, Bond JH, Winawer S, et al. Quality in the technical performance of colonoscopy and the continuous quality improvement process for colonoscopy: recommendations of the U.S. Multi-Society Task Force on colorectal cancer. Am J Gastroenterol 2002;97:1296-1308.

13. Walsh RM, Ackroyd FW, Shellito PC. Endoscopic resection of large sessile colorectal polyps. Gastrointest Endosc 1992;38:303-9.

 




Editorial Board:
Manoop S. Bhutani, M.D.
Galveston, TX
William R. Brugge, M.D.
Boston, MA
Peter R. McNally, D.O.
Denver, CO
Iqbal S. Sandhu, M.D.
Salt Lake City, UT
Thomas J. Savides, M.D.
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