Training in removal of colorectal polyps requires the achievement of proficiency in handling of the colonoscope and knowledge of all the various techniques associated with polypectomy including when and how to use electrocautery, types of snares, hemostasis, and injection methods. The endoscopic removal of colorectal polyps has decreased the incidence, morbidity, and mortality of colorectal cancer.

Patient assessment and consent

Methodical preparation prior to a complicated polypectomy is crucial; unfortunately, it is commonly overlooked. As with all procedures, the endoscopist must know the patient in detail including: (1) comorbid diseases which may influence sedation administration; (2) medications, specifically anti‐thrombotic agents; and (3) lesion characteristics which may influence the equipment required, technical approach, and procedure duration.

It is mandatory to obtain informed consent. Such discussions should include the risks and benefits of polypectomy as well as its alternatives, including leaving the lesion in situ. It is inappropriate to perform a complicated polypectomy when a lesion is incidentally identified during colonoscopy and only standard colonoscopy consent has been obtained.

Timing

When possible, complicated polypectomy should be performed in the morning. This allows for adequate post‐procedure monitoring prior to discharge.

Endoscopy Team

Complicated polypectomy, as with training in complicated polypectomy, requires a team mentality; this includes the endoscopist, the nursing staff, and the anesthetist, where appropriate, appreciating and adapting to the various stages and dynamics of the procedure. Both the endoscopist and nursing staff must be aware of, and be familiar with, the available endoscopes, electrosurgical generator, snares, and auxiliary equipment.

General principles

The removal of colorectal polyps requires the ability to safely transect a polyp with minimal bleeding while maintaining the integrity of the colorectal wall. Most colorectal polyps are successfully transected using the snare technique. Small polyps, up to 9 mm in diameter, have small nutrient blood vessels and are successfully removed by “cold” snare transection (without the application of thermal energy) with no significant bleeding. Recent medical literature has reported the safe transection of large polyps using the cold snare method. This technique is being studied to learn if it can be added to the main stream polypectomy armamentarium.

The majority of polyps less than 1 cm in diameter are benign, and can easily be removed by standard polypectomy techniques [1–3]. Sessile polyps over 1 cm in size are called lateral spreading lesions (LSLs) that spread along the epithelium [4]. These lesions are of importance as they are more likely to harbor cancer [4].

Most polypectomies are performed without any blood loss because hemostasis during polypectomy is very similar to hemostasis in any type of bleeding: pressure on a blood vessel to stop the flow of blood. In polypectomy, that principle is achieved by squeezing a blood vessel with the snare in order to occlude the vascular channel prior to applying a shearing force with a cold snare or heat sealing these occluded vessels with thermal energy. By tightly closing the snare around a polyp, the blood vessel walls are coapted in a similar fashion to that employed for cessation of hemorrhage from an ulcer in the upper gastrointestinal tract. In a bleeding gastric ulcer, for example, hemostasis is usually achieved by pushing on a vessel with a probe (BICAP) to occlude the vascular supply and then applying heat, which obliterates the vascular channel.

The electrosurgical unit

It is important for the successful achievement of polypectomy to be aware of the electrosurgical unit that is employed for polypectomy. There are no generally accepted criteria for the type of current that is used for polypectomy, nor for the amount of energy delivered during polypectomy. The type of electrocoagulation current for snare polypectomy varies from none to pure coagulation to a blended current, while others employ endocut capability, whereby short millisecond bursts of cutting current are followed by coagulation current on an alternate basis. Pure cutting current is not used for polypectomy since this type of energy explodes cells, including vascular structures, and delivers no hemostasis.

Coagulation current tends to heat tissue and will seal a coapted blood vessel if squeezed tightly by the snare. Experience has shown that there is no need to strangulate a polyp and see it turn purple before current application: once closed tightly around a polyp, a burst of coagulation current may be given and then current application maintained along with slide bar retraction until severance is achieved. Blended current, a combination of cutting current and coagulation current, is used by some, but does have the propensity to explode cells (cutting current property may result in immediate post‐polypectomy bleeding). Microprocessor‐controlled electrosurgical generators are becoming the standard of care for performing polyp resection. They provide a range of current settings including endocut mode with impedance‐dependent power output regulation. This provides relatively rapid tissue resection while minimizing the risk of undesirable deep mural injury. In general, a low setting on the electrocautery unit can be successfully used for polypectomy in the colorectum, without the need to vary the current setting for polypectomy on the left or right side.

The heat produced by snare activation is localized to the area around the wire loop, but the thermal effect may also spread toward the muscularis propria and the serosa. With prolonged application of pure coagulation current, it is possible for the thermal effect to damage the full thickness of the colorectal wall, resulting in symptoms that mimic a perforation. The distended wall is quite thin, measuring about 1.4–2.3 mm on endoscopic ultrasound (EUS) reports [5, 6]. These studies have demonstrated that there is no “thick area” in the sigmoid colon where the endoscopist can feel complacent in snare application because of the perceived notion that the sigmoid is much thicker than the right colon.

An adenoma actually replaces the mucosal surface and removal of the polyp leaves only a portion of the submucosa along with the muscularis propria and serosa, having a total thickness of less than 1.5 mm of tissue. The larger the polyp, the greater will be the volume of tissue within the snare loop and more thermal energy will be required to sever the polyp. The increase in energy required to sever a large polyp or a large portion of a polyp using coagulation current may result in a full thickness burn, which can ultimately result in a perforation.

Carbon dioxide

Complex polypectomy is safer with the utilization of carbon dioxide (CO₂) insufflation. The rapid absorption of intraluminal CO₂ mitigates post‐procedural pain. Moreover, in the uncommon event of luminal perforation, tension pneumoperitoneum is avoided and precise mural closure can be carefully executed. In a large single‐center prospective observational cohort of LSLs ≥ 20 mm, CO₂ insufflation compared to air insufflation was associated with a significant decrease in post‐procedure admissions [7].

Snares for polypectomy

Any type of snare may be used whether round, oval, or hex shaped, but the size should correspond to the diameter of the polyp. Stiff snares are preferred to facilitate precise tissue capture, particularly in flat and challenging lesions. However, it is important to appreciate the potential need for several different snares to successfully perform endoscopic mucosal resection. This is especially true for complex lesions. After several applications of a snare, the wire loop can become distorted, primarily because of the pulling force on the snare wire exerted during snare closure. As the slide bar on the snare handle is retracted during polypectomy, there is considerable pressure on the pointed tip of the snare as the polyp is squeezed between the tip of the wire and the tip of the snare sheath. As the loop is being retracted into the sheath during polypectomy, the wires at the tip are squeezed tightly together so that the next opening of the wire loop may not result in as wide a diameter as exists in a virgin snare. This happens with repeated use of a snare or during resection of multiple polyps in the same patient. The distortion of the wire loop may be reversed by withdrawal of the snare from the colonoscope, and with the wire loop opened, manually spreading the wires apart, reconstituting the normal shape of the loop. This stretching can also make a loop wider to fit around a larger polyp if necessary. One aspect of wire distortion that is difficult to overcome is twisting of the loop that distorts it from opening in a flat plane. When the wire loop can no longer be applied in a flat manner, the snare should be discarded.

During snare application of any polyp, it is important to place the tip of the snare sheath at the point at which closure is desired. With a pedunculated polyp, the desired location is usually considered to be at the midpoint of the stalk. The end of the snare sheath is the fixed point in the snare closure system, and the tip of the wire always retracts toward the tip of the sheath. In the case of a pedunculated polyp, once the wire loop is placed around the stalk, closure of the snare wire will be toward the tip of the sheath, which should be placed on the pedicle where transection is to occur, either at the midpoint of the stalk or close to the colon wall if there is a concern about malignancy. If, however, the wire loop catches on the interstices of the frond‐like head of a polyp, it is possible to inadvertently draw a portion of the polyp head into the closing loop and have part of the polyp head caught into the loop along with capture of the pedicle. The application of electrocurrent to the closed snare will therefore cut across part of the head of the polyp as well as the stalk.

Sessile polyps larger than 2 cm in diameter should be resected in piecemeal fashion. Because the colon wall is thin [5, 6] and the muscularis propria is not a strong or thick muscle, it is possible that closing the snare around a large sessile polyp may capture not only the submucosa, but also the muscularis propria and serosa so transection may completely cut through the entire thickness of the colon wall, resulting in a perforation when the polyp is severed. In order to prevent this complication, fluid is injected into the submucosa to elevate the polyp away from the deeper tissues, greatly expanding the submucosal layer. This fluid injection will separate the mucosa from the muscularis propria and serosa, resulting in the ability to close the snare around an adenoma and minimizing the possibility of catching deeper tissue in the snare loop during closure.

The snare handle as an information center

Safety in snare polypectomy can be enhanced by using the snare handle as an information system [8].

All snares are made with a thumbhole on the end of the handle and a two‐ring slide bar that moves along the handle shaft. The slide bar opens and closes the snare in a direct 1 : 1 ratio. A mark can be made on the handle shaft that will transmit information to the person who closes the snare. This mark is made by the assistant prior to polypectomy. The technique: partially close the slide bar; watch the tip of the wire loop as it retracts into the sheath and stop slide bar movement when the tip of the wire meets the tip of the sheath. Any further closure of the slide bar will move the tip of the wire into the sheath. At the closure point where both tips are at the same location (the tip of the wire is at the tip of the sheath), a mark should be made on the handle shaft where the slide bar has been stopped. This is called the “closure point” or “the line.” This mark should be made toward the thumbhole side of the slide bar. With a marked handle, the assistant will never inadvertently guillotine a polyp because he/she will look at the handle shaft and stop slide bar motion at the line that has been inscribed on the handle shaft (the closure point). This is an extremely useful tool when dealing with small polyps, since the trained assistant always stops at “the line,” which will prevent slicing off small polyps or soft polyps which do not have any “closure sensation” as the slide bar is retracted. Oftentimes, it will be desired to “cold cut” or “cheese wire” a small polyp to guillotine it without electrocautery current; however, this should be at the discretion of the endoscopist and not inadvertently severed by the gastrointestinal assistant as the snare is closed. The mark (line) on the handle shaft will always signal the assistant to use that as a stop mark before further slide bar closure.

This same mark can very effectively be used during removal of larger polyps in order to promote safety during polypectomy. There is a 1 : 1 correlation with the amount of wire loop that extends beyond the tip of the snare sheath and the slide bar. Often, as the slide bar is retracted around a large polyp, there is a “closure sensation” to the assistant as the volume of the polyp resists further slide bar movement. This resistance to further closure is usually felt as a “spongy” or “rubbery” sensation. For relatively small polyps or very soft polyps, the “closure sensation” may not be felt until the slide bar has reached “the line” and indeed, there may be no “closure sensation.” However, the assistant should stop at the line to prevent slicing the polyp off the wall. If the closure sensation is reached when the slide bar is at the “line,” it means that the polyp base has been compressed to a small size. Although the diameter of the base may be 1–2 cm, it frequently is compressed during snare closure so that the “closure sensation” is perceived when the slide bar is at or just a few millimeters from “the line.” On the other hand, if a polyp whose base is 2 cm in diameter is captured, and the assistant perceives the closure sensation when the slide bar is several centimeters from the line, that information should be transmitted to the endoscopist, since that is an indication that a significant amount of snare wire is outside the sheath, and the wire loop may have engaged a large portion of mucosa, submucosa, and perhaps serosa within the tightened loop. An attempt at cutting through the polyp at this point may cause deep injury to the wall of the bowel. Given the information that closure sensation is felt when the slide bar is several centimeters from the line, the endoscopist must consider various scenarios: that the polyp is large and the distance from the line to the slide bar is consistent with the size of the polyp and the application of current should commence; the wire loop is tangentially placed across the polyp, has closed around a large section of the polyp, and was not applied parallel to the colon wall or the snare has caught a large piece of tissue behind the polyp that has been drawn into the closed loop. If this has occurred, the loop should be repositioned in order to avoid transecting a portion of the normal colon wall.

Safety in snare handling

Once the tip of the sheath has been advanced into view and before the assistant is requested to open the snare, the tip of the sheath should be pointed toward the lumen and not directly toward the colon wall. The extruded pointed tip of the wire loop can easily penetrate the colon wall if opened rapidly when it is close to the mucosal surface. Conversely, the fully opened wire is quite flexible and can be pushed against the wall either to anchor its tip during entrapment of a polyp or can be pushed on the wall to widen the loop to place it over a large polyp. A safety measure to permit the endoscopist to have full control over the snare is as the assistant opens the loop, the endoscopist simultaneously withdraws the sheath into the instrument channel while the snare wire is being extended. The assistant should open the loop fully as the sheath is being withdrawn by the endoscopist. In this manner, the opened wire loop is almost completely within the instrument channel. When positioning of the snare over the polyp is desired, the sheath can be pushed out and the wire loop will open as it exits from the tip of the scope. The operator then has complete control over the length and width of the loop as it opens by pushing or pulling on the sheath and no longer requires the assistant to open and close the snare because it has been fully opened and is lying within the instrument channel.

Techniques for successful removal of sessile polyps

In order to successfully perform polypectomy, the endoscopist must have excellent control of the instrument at all times during the procedure, especially during the snare capture of a polyp and when applying electrical current. The skill and knowledge of colonoscopy techniques can only be acquired through performance of multiple diagnostic examinations prior to attempting polypectomy. The endoscopist should start polypectomy with small polyps. Once familiar with the technique of placing the snare over a polyp, closing the snare, and application of electrocautery current while keeping the polyp properly in view with the instrument in a stable position, the endoscopist can move on to larger polyps. There is limited literature on the learning curve concerning removal of large polyps, but since the same techniques required for colonoscopic polypectomy of small‐ and medium‐sized polyps are used in removing large polyps, once high‐quality resection technique is learned, it is recommended to watch several being performed and then to achieve competency under expert supervision before embarking on the task of removing large sessile polyps.

It is important to fully assess a polyp before beginning polypectomy. High‐definition colonoscopes equipped with enhanced imaging technology (e.g., narrow‐band imaging (NBI) (Video 21.1) and dual‐focus technology; Olympus; Tokyo, Japan) have allowed endoscopists to predict a lesion’s histology prior to resection (Figure 21.1). In cases of well‐differentiated cancer with superficial invasion (<1,000 μm) into the submucosa, termed superficial submucosal invasive cancer (S‐SMIC), en bloc endoscopic mucosal resection (EMR) with R0 resection is considered curative [9]. There is a size limitation of en bloc resection; LSLs < 20 mm with features suggestive of S‐SMIC should undergo en bloc EMR, whereas LSLs ≥ 20 mm should be considered for endoscopic submucosal dissection (ESD). If features of deep SMIC (>1,000 μm) are identified, surgical referral is most appropriate.

A lesion’s risk of SMIC is dependent on: (1) location; (2) size; (3) morphology as defined by the Paris classification [10, 11]; (4) surface topography (granular (Figure 21.2), non‐granular, mixed); (5) surface pit pattern [12]; and (6) surface vascular pattern [13]. Pit pattern and vascular pattern evaluation is commonly viewed as a daunting endeavor given the multitude of published classification systems. This includes the Kudo Pit Pattern [12], the Sano Vascular Pattern [14], and more recently the NBI International Colorectal Endoscopic (NICE) classification [13] and the Japan NBI Expert Team (JNET) classification [15]. Practically, a key feature underpinning all lesion assessment and the application of classification systems is that benign neoplasia has a relatively homogenous surface pattern and is devoid of a demarcation line, whereas invasive features are characterized by a demarcated area, which contains a disrupted surface evident in either the pit pattern or vascular pattern (Video 21.2), but usually both [16].

Despite these advances in optical evaluation, there is a risk of invisible or “covert” SMIC. This concept was recently evaluated in a prospective multicenter observational cohort of 2,277 LSLs ≥ 20 mm [17]. After excluding lesions with visible or “overt” SMIC, rectosigmoid location, size, non‐granularity, and 0‐Is or 0‐IIa+Is Paris morphology [10] were significantly associated with SMIC on multivariable analysis. Importantly, combining Paris classification, surface topography, and lesion location stratified certain LSLs into a high (>10%) covert SMIC risk grouping, thereby identifying potential candidates for ESD. This concept of covert SMIC is especially important in the rectum, where minimization of unnecessary surgery is paramount due to a heightened risk of surgical morbidity and stoma formation [18].

Another benefit of image‐enhanced endoscopy is the edges of the lesion can be more clearly defined by the use of chromoendoscopy or virtual chromoendoscopy (Video 21.3).

The techniques that must be learned for polypectomy [19] are as follows:

1. Use an appropriate size snare that is optimal for the polyp size. Most polyps are 1 cm or less, and it is easier to capture these with a small snare (10 mm). It is often difficult to capture a small polyp with a larger snare (15–20 mm), which must be almost fully extended before the arms of the wire loop expand sufficiently to capture a polyp. Having to extend the wire to its full extent to capture a polyp can often be problematic because the folds and bends of the colorectum may prevent the ability to fully open the snare.
   
2. Prior to beginning EMR, patient position and lesion orientation should be optimized. This is to maximize procedure efficiency and success. If required, transition the patient to either supine position or right lateral decubitus position to shift the fluid pool to the opposing colonic wall. Subsequently, rotate the endoscope to position the lesion at 6 o’clock (Figure 21.2). This is to align the lesion with the working channel of the colonoscope (Video 21.4). It is extremely difficult to have the snare encircle a polyp located in the 12 o’clock or 9 o’clock position in the visual field. Lastly, a retroflexed position, facilitated by using a pediatric colonoscope or a gastroscope, can optimize lesion visualization and access.
   
3. Place the snare over the polyp with the wire in the plane of the surrounding mucosa so that it lies flat on the mucosal surface. This maneuver ensures that the snare will close at the junction of the polyp and mucosal surface. Be mindful that the tip of the sheath is the stationary portion of the snare complex, and the open wire always retracts to the tip of the sheath. A stiff snare is useful since it can be pushed against the mucosal surface around the polyp and it will remain flat to encircle the lesion. A flexible wire often will bend at the junction with the sheath and when the sheath is pushed against the colon wall, the wire loop will rise up and no longer remain flat on the colon wall. If closure occurs with the snare in this position, the snare will capture a tangential part of the polyp, leaving a portion on the proximal edge, which then has to be further resected. One of the important aspects of polypectomy is to keep the snare wire flat on the wall during closure.

   

   

   
   
4. Aspirate gas once the snare is in place. The aspiration of gas causes the entire circumference of the colon to become smaller and its diameter to decrease. The decrease in circumference causes the polyp to actually rise up within the snare that has been placed over the polyp. This occurs because as the circumference decreases, the footprint of the polyp also decreases. Since the polyp volume does not change in size as its base gets smaller, the polyp actually elevates into the snare. Frequently, aspiration results in loss of visual contact with the closing snare since folds may collapse over the polyp. Even if the snare capturing the polyp cannot be readily seen, the assistant is asked to close the snare to the mark or until there is a closure sensation. Before polyp transection, gas is then re‐insufflated and an assessment is made with full visualization as to the relationship of the snare to the polyp. If only part of the polyp has been captured, the snare can be opened and repositioned.
   
5. The completely closed snare should feel “spongy.” If the closed snare feels hard to the operator, muscularis propria may have been inadvertently captured by the snare. There may also be “puckering” of the surrounding mucosa. To address this, gently elevate the captured tissue toward the center of the lumen. While simultaneously insufflating, open the snare slightly to release the muscularis propria, then close the snare. The closed snare should be jiggled back and forth by holding the sheath near the biopsy port and moving it in and out. This maneuver will provide visual confirmation that a large piece of the colon wall has not been captured within the snare loop behind the polyp (and out of sight). Entrapped proximal mucosa will result in the colon wall behind the polyp, also moving back and forth as the snare is jiggled.
   
6. Once the snare is closed snugly onto the polyp, some endoscopists acquire the snare handle from the assistant to complete the resection, as this can provide critical tactile information. Most endoscopists ask the knowledgeable assistant to close the snare for polyp transection while the operator uses the foot switch to supply electrocautery current. The assistant (or the person who closes the snare) should not begin snare closure until requested by the endoscopist. In training circumstances, it is not unusual for the trainee, deeply involved in snare position, gas aspiration, and then re‐insufflation, maintaining the polyp in sight, and application of electrocautery current with the foot switch, to forget to ask the endoscopy assistant to close the snare. Often the nurse/assistant will have considerably more experience in polyp removal than the trainee and the result is that the nurse/assistant will close the snare without waiting for the request from the trainee endoscopist. However, once becoming familiar with the techniques of polypectomy, it is better to have the assistant wait until requested by the endoscopist to begin snare closure. This request for snare closure should be made after having briefly activated electrosurgical energy. With small polyps, snare closure will be relatively rapid and as soon as the foot switch is pressed, the request may be given to close the snare. However, if a polyp has a thick pedicle, usually a few seconds of electrosurgical current should be given prior to snare closure.

Once foot switch application has started the flow of current, the foot switch should be pressed continuously until the polyp has been severed. However, some endoscopists in control of the snare prefer to tap the electrocautery pedal. For all sessile polyps over 1 cm in diameter, the technique is the same. These include placing the open loop directly over the polyp, keeping the snare flat on the wall, aspiration of gas, and then snare closure. Tissue resection is relatively rapid when using fractionated current (alternating cutting/coagulation sequentially in milliseconds) but a longer resection time should raise concern for desmoplasia or captured muscularis propria. After each resection, the defect should be irrigated. This expands the defect and allows for evaluation of incompletely resected tissue and deep mucosal injury. Perform subsequent resections by aligning the snare with the edge of the mucosal defect. If submucosal injection was used, repeat injection (after every 2–4 resections) and subsequent resection should be performed until the entire lesion is successfully removed (Figure 21.3) [20]. Even diminutive residual adenoma at the edge of the defect must be excised and thermal ablation of visible residual adenoma should not be relied upon to complete the polypectomy, although many use current to ablate this tissue.

Special techniques for sessile polyps

Underwater mucosal resection is possible using electrosurgical current [21, 22]. Reducing tension from gaseous distention results in a more protuberant lesion which can be more readily resected [23]. Few studies have been reported.

Small colon polyps may be removed without electrosurgical current [24]. Studies are underway [25–27] to resect large sessile lesions using cold snare techniques. Resection without the use of cautery appears to cause less post‐polypectomy bleeding.

Pedunculated polyps

Pedunculated polyps are relatively easy to remove, since the snare wire only needs to be placed on the pedicle and tightened prior to the application of electrocautery current. If the pedunculated polyp is large, the pedicle is often thick and may be of variable length. When a large pedunculated polyp is seen, it should be moved around with the closed snare sheath in an attempt to ascertain the location, width, and length of the stalk and its relationship to the colon wall. Once this has been established, the colonoscope should be passed proximal to the polyp into an open area of the lumen. The scope is then rotated so that the polyp attachment is at the 5 o’clock position. With the standard snare fully opened, and the sheath tip near the tip of the colonoscope, the colonoscope, and snare should be withdrawn slowly until the leading edge of the polyp is visualized or the attachment of the polyp is seen if the head is pointed toward the anus.

Upon withdrawal of the colonoscope, the open wire loop is dragged along the colon wall over the polyp when the head is in a proximal position. As the scope with wire loop extended is withdrawn while holding the shaft with the right hand, the scope can be torqued to the right or to the left in order to place the loop over the polyp. If the snare cannot fully capture the polyp, left/right rotation of the shaft can help to engage other portions of the polyp as withdrawal continues. After the shaft of the colonoscope with its wire has been withdrawn to the point where the pedicle is identified, slow closure of the snare handle should be accomplished as the endoscopist steadies the scope and moves the right hand from the shaft of the instrument to the snare sheath advancing it as closure is accomplished.

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