Colonoscopic Polypectomy
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Diagnostic and Therapeutic Endoscopy, Vol. 6, pp. 111-124 (C) 2000 OPA (Overseas Publishers Association) N.V. Reprints available directly from the publisher Published by license under Photocopying permitted by license only the Harwood Academic Publishers imprint, part of The Gordon and Breach Publishing Group. Printed in Malaysia. Colonoscopic Polypectomy JEROME D. WAYE* Mount Sinai Medical Center," GI Endoscopy Unit, Mount Sinai Hospital, GI Endoscopy Unit, Lenox Hill Hospital (Received 4 October 1999," Revised 7 December 1999," In final form 21 December 1999) Colonoscopic polypectomy is a major advance in the therapy of colon neoplasms. The techniques for safe and efficient polyp removal are described. The uses of a variety of ancillary devices are discussed, including clips, loops, submucosal injection of fluid, and several thermal probes, including the argon plasma coagulator. The location of a lesion may be difficult to ascertain by intracolonic landmarks, but can be more precisely determined by X-ray, magnetic imaging, or intraoperative colonoscopy. Alternatively, it is possible to permanently mark the site of polyp removal with a carbon particle submucosal injection to facilitate subsequent localization either by surgery or interval colonoscopy. Keywords." Marking, Problems, Safety, Submucosal injection, Technique INTRODUCTION tends to separate a polyp more rapidly than does coagulation alone. Once adjusted to the optimal The removal of colonic polyps is a major advance in setting, there is no need to change the power output medicine. Polypectomy was first introduced thirty during polyp removal, regardless of whether the years ago, and it has markedly changed the way base is large or small or when switching between the polyps and cancer are treated. Polypectomy is safe polypectomy snare and the hot biopsy forceps. and is currently the only (but not the absolute) method for prevention of colon cancer by interrupt- Endoscopes ing the polyp-cancer sequence. A single-channel 168 cm-long colonoscope with a channel EQUIPMENT large accessory is the instrument most pre- ferred for colonoscopy by all experts and most colonoscopists. The double-channel scopes are Electrosurgical Unit somewhat less flexible, can be difficult to pass Most experts use pure coagulation current during through the entire colon, and are associated with polypectomy, and eschew blended current, which more patient discomfort than the one-channel type. Address for Correspondence. 650 Park Avenue, New York, NY 10021, USA. Tel." +1-212-439-7779. Fax: +1-212-249-5349. E-mail: [email protected]. lll 112 J.D. WAYE There are only limited occasions when it is desired to of tissue can be varied from to 3 mm. In the pass two accessory devices simultaneously through colon, the power output setting should usually be at a colonoscope, such as grasping a polyp and lifting it 40W, with a relatively low gas flow (0.8 L/rain). while placing a snare [1-3]. This maneuver would Uses in the large bowel include treatment of post- appear to be relatively easy, but in practice can be polypectomy bleeding and ablation of residual ade- quite difficult, since the two accessories are obli- nomas following their piecemeal resection [4-6]. gated to move together rather than separately; it is The delivery system for flexible endoscopy was desirable to lift up the portion grasped by the forceps developed in Germany (ERBE, Inc., Tubingen, while seating the snare downward over the polyp, Germany) [7,8]. but such manipulation is not possible. Loops and Clips Hot Biopsy Forceps Two additional devices are available for polypect- The hot biopsy forceps is an electrically insulated omy. These are the detachable snare loop and clips. forceps through which electrical current flows to The loop, used for hemostasis during or after direct electrical energy around the tissue held within polypectomy, is a nylon ligature that can be placed the jaws, enabling simultaneous cautery of a polyp over a lesion (such as a pedunculated polyp) and base while obtaining a biopsy specimen. tightened with a one-way silicone-rubber stopper, which prevents opening of the loop after it has been closed [7]. The fully assembled mechanism, with an Thermal Devices accompanying over-sheath (to permit the soft nylon Two contact thermal devices, the heater probe and loop to pass through the instrument channel), is Bicap electrode, can control post-polypectomy arte- the same caliber as a snare. Once extruded from the rial spurting as well as lesser degrees of hemorrhage. end of the delivery system, the loop is maneuvered When used for control of colonic hemorrhage, the around the head of a polyp under direct vision and, current should be decreased by approximately 50% after tightening, is separated from the insertion tube from the power used for treatment of upper intes- [9]. When attempting to encircle large polyps, the tinal hemorrhage. Multiple applications at a low floppy nylon loop not having the same tensile power setting appear to be safe in the colon. There strength of a wire snare may become caught in the should not be a great deal of force as is recom- polyp head, resulting in the inability to pass the loop mended in the upper intestinal tract. The water jet completely over the polyp. If the loop becomes from these probes is extremely useful for precise enmeshed in the polyp head, closure of the loop will localization of the bleeding site to permit precise result in tangential placement interfering with snare probe application. positioning. If the head is encircled successfully, it is The argon plasma coagulator is a device for the necessary that the loop be placed on the pedicle far delivery of high-frequency current in a monopolar enough toward the colon wall to allow transection mode that does not require direct contact between of the stalk above the loop with sufficient margin to the probe and tissue. When the distance from probe ensure safety if the polyp contains invasive cancer. to tissue is optimal, the monopolar circuit is com- After placement close to the bowel wall, polypect- pleted by the flow of electrons through the activated omy is performed above the loop-ligature. Transec- and ionized argon gas which transmits the electrical tion of the pedicle close to the loop may cause ions from the probe electrode to the tissue. The the loop to slip off with immediate bleeding as a ionized argon gas is called the argon plasma. Uti- complication. Placement prior to polyp removal lizing a combination of voltage adjustment and may result in difficulty with snare placement motion of the probe tip, the thermal penetration because of the long "tail." Because immediate COLONOSCOPIC POLYPECTOMY 113 post-polypectomy bleeding only occurs in about 1% The clips may also be used for hemostasis [13] ofcases [10], an alternate use of this device is to place (Fig. 1). The ability to rotate the clip permits more it on the resected stalk to ensure hemostasis post- precise placement [14]. The clips are especially useful polypectomy, although tissue retraction may flatten for bleeding from flat polypectomy sites [15]. They the residual pedicle to the extent that the loop have also been used successfully to stop arterial cannot be properly seated [11]. The loops sponta- bleeding from the severed stalk of pedunculated neously slough in 4-7 days, and endoscopy follow- polyps. It is theoretically possible to apply a clip ing detachment of the loops shows residual shallow onto the base of a pedunculated polyp close to the ulcers. The loop and carrier device (HX-20) are bowel wall and snare the polyp above the clip using manufactured by Olympus Inc.; the loop is available standard snare techniques [16]. It is important that in two sizes, 2.5 and 4.0 cm. the wire snare does not touch the metal clip, which Mucosal clips have been available for several may result in a burn ofthe colon wall. The clips spon- years. These small clips are useful for temporary taneously dislodge within several days, although marking of lesions, to identify the distance reached some may remain for long periods. Both loops by the colonoscope [12], and to mark the edges of and clips may be used prophylactically in patients tumors prior to expandable metal stent placement. with disorders of coagulation either spontaneous FIGURE Clips placed on a bleeding site to control immediate post-polypectomy bleeding. 114 J.D. WAYE or iatrogenic (Coumadin) when there is a risk of Patients with polyps of any size that can be subsequent bleeding. removed endoscopically do not require hospitaliza- tion. Even the largest polyps may be removed totally, with or without submucosal injection poly- Snares pectomy techniques, on an outpatient basis or in an The standard large snare is about 6 cm in length by ambulatory office setting. 3 cm wide, and the small snare is 3 cm long by cm wide. The technique of application is the same in Polyp Size all instances, whether the snare is oval, crescent- The majority of polyps (about 80%) are relatively shaped, or hexagonal. The diameter of the wire is an small, being less than cm in diameter. All large important consideration, since thin snare wires will polyps (greater than 35 mm) are adenomas and cut through a polyp faster than a thick wire [17]. are usually located in the rectum or right colon. A bipolar snare [18] is available but does not have Most small (less than 5 mm) polyps in the rectum any benefit over the standard monopolar electro- and distal sigmoid colon are non-neoplastic, but cautery snare. Rotatable snares are considered throughout the remainder of the colon, approxi- unnecessary by most endoscopists. mately 60-70% of small polyps are adenomas [19]. Fifty percent of patients with one adenoma will have another, and it is important to perform total PROCEDURE colonoscopy to seek synchronous adenomas.