40
Polypectomy

George Gershman, Mike Thomson, and Gabor Veres

Principles of electrosurgery

The cornerstone of electric cutting and coagulation of living tissue is the heating of the restricted area by radiofrequency (RF) alternating current without stimulation of nerves and muscles. When current alternates up to a million times per second, it does not stimulate muscle and nerve membranes long enough to induce depolarization before the next alternation occurs. Cutting is produced by rapid and strong heating, which creates evaporation of intra‐ and extracellular fluids.

Coagulation is initiated when the speed and degree of tissue heating are slower and less intense, leading to cellular desiccation. Specific effects of different types of RF currents and heat‐related tissue destruction are illustrated in Figures 40.1 and 40.2.

Several factors regulate the degree of tissue heating.

Voltage (V) is the force required to push current through the tissue. The higher the voltage, the deeper the thermal tissue destruction.
Tissue resistance (R) or impedance (for alternating current) is the force generated by tissue to resist electrical flow. It is directly proportional to the amount of tissue electrolytes. Resistance increases dramatically during tissue heating and desiccation. Normal tissue resistance is not uniform; it is lowest along blood vessels and highest at the level of the skin.
Time (T) is an essential factor of energy (E) regulation, which can be expressed as:

Schematic illustration of different types of alternating RF currents and specific tissue response. — **Figure 40.1** Different types of alternating RF currents and specific tissue response.

Tissue heating increases with time, although the process is quite complex.

Heating produces water loss and increases resistance.
Increasing resistance shifts the distribution of current from the lowest resistance pathway.
Fluctuation of resistance affects the power output produced by the generator.
Some of the released heat is removed from high‐temperature areas by blood flow. The cooling effect of blood flow explains why the same energy applied to the tissue generates less destruction if delivered slowly.

Current density is a measure of RF current (I) which flows through a specific cross‐section area:

The amount of heat generated in tissue is directly proportional to the power density (P) expressed as a square value of current density multiplied by resistance:

This important equation implies that power density has an inverted relationship with the square of the cross‐sectional area (πr²). It means that even a small tightening of the loop produces a profound effect on tissue heating. This can be illustrated by the polypectomy of a 1 cm polyp.

If a snare decreases the diameter of a polyp by half, the cross‐sectional area at the level of the loop will be only 0.2 cm². It is four times less than a cross‐sectional area at the base of the polyp and about 500 times less than a cross‐sectional area of skin under a 10 × 10 cm plate of the return electrode.

Schematic illustration of temperature-related tissue destruction always induced by RF current. — **Figure 40.2** Temperature‐related tissue destruction always induced by RF current.

If 0.2 A electric current is applied through the snare, it produces a current density of 1 A/cm², 0.25 A/cm² and 0.002 A/cm² at the level of the loop, polyp base, and skin respectively.

The fall of the power density (i.e., power actually delivered to the tissue and generating heat) is even more dramatic: from 1 A/cm² × R at the level of the loop, to 0.06 A/cm² × R and 0.000004 A/cm² × R at the base of the polyp and skin under the return electrode respectively. Narrowing of a cross‐sectional area by a closing snare produces the most significant effect on heat production compared with increasing the power setting and time of electric current application. It also allows one to perform a polypectomy at a lower power using a coagulating mode safely.

The law of current density is vital for polypectomy. Narrowing of a cross‐sectional area is the most important safety technique, which produces coagulation of the core vessels of the polyps before cutting, restricts the area of maximal tissue heating around the loop, and limits tissue destruction of the deep bowel wall layers.

Snare loops

Commercially available snares vary by size, configuration of loop, design, mechanical characteristics of handles, and wire thickness. Reusable snares often lose their mechanical properties and can peel and break at the tip. Disposable snares are more durable and predictable. The thickness of the wire loop and handle “attitude” can significantly affect the results of polypectomy. Snares with thick wire loops have two important advantages.

A decreased risk of snapping a polyp without adequate coagulation.
A large surface contact with tissue resulting in better coagulation.

A standard snare with an opening diameter of 2.5 cm can be used for different size polyps. A special small or “mini” snare (1 cm loop) has been designed for polyps less than 1 cm. It is important for endoscopists to find an “optimal” snare for routine practice in order to avoid any unexpected “surprises” during cutting or coagulation.

The chosen snare should be fully open and then closed to the point when just the tip of the wire loop is outside the outer sheath. Marking of the so‐called closing point on the handle of the snare (Figure 40.3) serves two important safety features.

Protection from premature cutting of a small sessile or pedunculated polyp without adequate coagulation.
Alerting the endoscopist of a partial polyp’s head entrapment or underestimation of the stalk size.

It is very important to check how far the tip of the wire loop is retracted into the outer plastic sheath when the snare is fully closed. A distance of 15 mm provides adequate squeezing pressure (Figure 40.4). If the stalk of a large polyp is not squeezed adequately, this compromises the coagulation of core vessels for two reasons.

Photo depicts snare preparation before polypectomy describes the marking of the so-called closing point on the handle of the snare. — **Figure 40.3** Snare preparation before polypectomy: marking of the so‐called closing point on the handle of the snare.

Photo depicts squeezing pressure described by a 15 mm retraction of the wire into the plastic sheath provides an optimal narrowing of the polyp base or the stalk for adequate constriction of the blood vessels and generation of an appropriate power density. — **Figure 40.4** Squeezing pressure. A 15 mm retraction of the wire into the plastic sheath provides an optimal narrowing of the polyp base or the stalk for adequate constriction of the blood vessels and generation of an appropriate power density.

Blood vessels remain open and blood flow continues, producing a cooling effect;
More importantly, the cross‐sectional area is not narrow enough to concentrate the current flow to an appropriate power density to coagulate core vessels.

Closure of a snare loop with excessive pressure can induce premature cutting before coagulation. Both conditions could lead to significant bleeding.

Routine polypectomy

Polypectomy is the most common therapeutic procedure in pediatric GI endoscopy. It can be simple or more complex, depending on the size or location of the polyp and personal experience. No matter how comfortable the endoscopist is with the polypectomy technique, it is always wise to follow a simple rule: safety before action.

Safety routine

A proper assembly and settings check of the electrosurgical unit before each polypectomy should be routine to avoid accidental delivery of excessive power to the tissue. The foot pedal should be conveniently positioned in front of the endoscopist. The polypectomy snare should be checked for smooth openingchecked for smooth opening, thickness of the wire, adequate squeezing pressure, and closing point. It is useful to create a kit of hemostatic accessories such as endo‐loops, metal clips, and needle for epinephrine injection.

Preparation and techniques

Good bowel preparation is essential not only for optimal positioning of the snare loop around a polyp stalk or sessile or flat lesion, but also to avoid accidental burning or coagulation of normal mucosa. A large amount of liquid or solid stool increases the chance of missing a small or even a good‐sized polyp. An obscure view often leads to excessive use of air and bowel stretching, making it thinner.

Unexpected patient awakening or movements complicate polypectomy, especially during a snare closure, and are avoidable by adequate sedation.

The technique of polypectomy consists of three important elements.

Optimal scope navigation.
Placement of a wire loop around the polyp.
Cold or hot snare polypectomy.

A 6 o’clock position is ideal for polypectomy. The location of a polyp between 4 and 5 or 7 and 8 o’clock is suboptimal. Polypectomy is very difficult and somewhat unsafe if a polyp is located on the upper aspect of a lumen between 9 and 3 o’clock.

An ideal 6 o’clock approach can be established by clockwise or counterclockwise rotation of the shaft and downward deflection of the tip. Careful assessment of the stalk size and location of the polyp is mandatory before polypectomy. Once an optimal position and clear view of the polyp are achieved, the scope is advanced toward the polyp base. An ideal distance from the tip of the scope to the polyp is 1–2 cm unless the polyp is hiding beyond a fold. To reveal the polyp, press the mucosal fold down with the tip of the endoscope or a closed snare.

All manipulations with a snare should be performed gradually.

It is good practice to open a snare just enough to embrace the polyp. Full opening of a snare makes the wire loop floppy and less controllable.

An adequately opened and horizontally oriented wire loop above a sessile polyp at 6 o’clock accomplishes snaring just by downward tip deflection. If an opened wire loop creates an angle at the base of the polyp, rotate the shaft of the scope toward the polyp until it is captured. Steer the shaft slightly away from the sessile polyp if it is located between 4 and 5 o’clock or 7 and 8 o’clock and attempts to establish an ideal 6 o’clock position have failed. Advance the snare toward the polyp and open the loop. Once the polyp is inside the loop (Figure 40.5), rotate the scope slowly toward the polyp to align the plane of the snare with the axis of the bowel lumen. Close the snare slowly and move it forward until it reaches the base of the polyp. At this moment, the snare should be completely closed (Figure 40.6).

Occasionally, backward snaring is more effective, especially if the polyp is more than 1.5 cm in length. Point a slightly open wire loop down towards the area where a polyp head touches the bowel wall. While the loop is slowly pushing forward, tissue resistance creates a bowing effect and facilitates loop opening. As a result, the loop slides between the mucosa and the polyp head. An additional clockwise rotation of the tip using both knobs swings a wire loop under the polyp head. Once a snare is positioned properly, it can be closed to complete polypectomy.

Photo depicts the polyp is within the wire loop. — **Figure 40.5** The polyp is within the wire loop.

Photo depicts the snare is fully closed. Avoid excessive force to prevent amputation of the polyp. — **Figure 40.6** The snare is fully closed. Avoid excessive force to prevent amputation of the polyp.

If the polyp is facing away from the tip of the scope, advance the snare and open it slowly until the tip of the wire is beyond the polyp’s head. Deflect the tip of the scope slightly down to move the wire loop below the polyp. Pull the snare back until the head of the polyp is inside the loop and the wire is just under the polyp head. Close the snare gradually and advance it toward the polyp to prevent sliding of the wire along the stalk.

Advancement of the snare towards the polyp during wire loop closure is a key element in polyp snaring. It secures the polyp within the loop and allows precise navigation of the snare. Capturing a small polyp with a standard snare may be challenging. A slight decompression of the bowel may elevate the polyp above the wire loop and facilitate its capture.

The technique of polypectomy is different when applied to small polyps less than 5 mm, broad‐based polyps more than 15 mm, pedunculated polyps more than 20 mm or polyps with a stalk ≥10 mm.

European Society of Gastrointestinal Endoscopy (ESGE) guidelines recommend cold snare polypectomy as the preferred technique for removal of diminutive polyps less than 5 mm. Diminutive colon polyps can also be removed safely by cold biopsy forceps (avoid hot biopsy forceps due to the potential risk of perforation).

Two helpful hints:

If a polyp is on the edge of a fold, position the tip of the colonoscope within a short distance (˂2 cm) from the target, open the forceps cup and orient it perpendicular to the fold, advance the forceps toward the polyp and close it when the polyp is within the cup. Avoid forcefully pushing the forceps up against the mucosa as it will stretch the tissue and result in suboptimal sampling.
If a small polyp is in between folds, place the forceps with opened cup horizontally to the folds and advance the forceps forward to the point when the polyp is within reach to grasp it.

An alternative technique consists of vertical orientation of the biopsy forceps and positioning the lower biopsy jaw just below the polyp to avoid grasping adjacent mucosa before closing the forceps.

Large sessile polyps are rare in children except patients with Peutz–Jeghers syndrome. Such polyps are usually located in the small intestine, primarily in the jejunum.

Broad‐based polyps >15 mm require a piecemeal polypectomy technique. A submucosal injection of epinephrine (1:10 000) solution before polypectomy decreases the risk of deep tissue injury. Injection at the proximal site of the polyp is performed first, followed by injection at the distal edge and lateral sides of the polyp base. Injection of 3–10 cc of the chosen solution in 3–4 sites is usually adequate to create a liquid “cushion” under the polyp. The needle should be oriented tangentially to minimize the risk of transmural injection.

The piecemeal technique consists of removal of the polyp in multiple tangential cuts. This significantly diminishes the risk of full‐thickness thermal injury of the intestinal wall and bleeding. Excessive closing pressure should be avoided because it may compromise initiation of cutting, due to lack of electrical arc from the active electrode to the tissue. In addition, decreased wire–tissue contact area increases current density, which may induce excessive desiccation and stop current flow.

En bloc polypectomy of sessile polyps ≤15 mm and pedunculated polyps ≤20 mm with a short stalk is safe if gentle wiggling of the snare with the captured polyp does not produce synchronous movements of the underlying bowel wall (the sign that submucosa and muscularis propria is not trapped within the wire loop).

Polypectomy of pedunculated polyps more than 2 cm is challenging. Attention should be paid to proper positioning of the wire loop at the narrowest portion of the stalk right below the polyp head. Thick blood vessels in the middle of the stalk require slow desiccation for complete coagulation and hemostasis before the final cut. For prevention of bleeding in pedunculated polyps with a head ≥2 cm or stalk ≥1.0 cm, ESGE guidelines recommend injection of dilute adrenaline and/or mechanical hemostasis. It has been shown that the use of endo‐loops or endo‐clips (Figure 40.7) can be superior to adrenaline injection, and a combination of mechanical prophylaxis with adrenaline injection significantly decreases postpolypectomy bleeding in comparison with injection alone.

Photo depicts mechanical prophylaxis of bleeding with endo-clips. — **Figure 40.7** Mechanical prophylaxis of bleeding with endo‐clips.

It is difficult to avoid direct contact of a large pedunculated polyp with normal mucosa during polypectomy. However, attempts should be made to keep the snared polyp close to the center of the bowel lumen to minimize thermal destruction of adjacent tissue. Careful inspection of a long stalk should precede any manipulations with the snare. The location of the polyp base and position of the long stalk are crucial for an optimal approach to the polyp. To capture the polyp, advance the snare toward the base of the polyp head and open the wire loop slowly until it becomes big enough to embrace the polyp.

Any additional manipulation with the snare should be coordinated with either right or left torque of the shaft toward the 6 o’clock direction. A backward snaring method may be useful. Reserve reduction of polyp size by piecemeal technique for the challenging cases.

A polypectomy can be performed during colonic intubation or the withdrawal phase of a colonoscopy. The decision is made based on polyp size. It is wise to remove a small sessile or pedunculated polyp as soon as it is discovered to eliminate the chance of missing it at a future time. Removal of a large polyp is more convenient after the entire colon has been inspected, except in cases when the position of a polyp is ideal for polypectomy. Careful examination of the colon, especially behind the folds, can be accomplished by circumferential rotation of the tip and the shaft, aspiration of excessive fluid and repeated insertion of the scope for a few segments if the bowel quickly slips away from the tip.

After polypectomy, polyps less than 10 mm can be easily sucked into the biopsy channel and eventually into a filtered polyp suction trap. Water irrigation and proper orientation of a suction nostril at the tip of a scope facilitate the recovery process.

A tripod forceps or Roth net is useful for retrieval of larger polyps (Figure 40.8).

Photos depict (a) tripod forceps. (b) Roth net. — **Figure 40.8** (a) Tripod forceps. (b) Roth net.

Nylon polyp retrieval nets or metal baskets can be used for removal of multiple polyps. Grasping of a large polyp using the snare is the most reliable way to bring it to the rectum. Manual assistance to recover a large polyp from the rectum after polypectomy may be necessary.

It is useful to pay attention to the direction in which the polyp falls after polypectomy. The first place to look for a “lost” polyp is in a pool of fluid. If the polyp is not there, flush some water and watch where it flows: backflow indicates that the polyp is distal to the tip of the scope.

Photo depicts hemostasis with argon plasma coagulation. — **Figure 40.9** Hemostasis with argon plasma coagulation.

Complications

Three types of complications can occur after polypectomy. The most common is bleeding. In contrast to adults, delayed bleeding within two weeks after the procedure is quite rare in children.

Immediate onset of bleeding is more common, although the incidence of this complication is less than 1% in children. This may reflect a smaller size, the number of polyps and the absence of co‐morbid conditions such as hypertension, atherosclerosis, etc. A slow oozing from the polypectomy site is easy to control by injection of epinephrine solution (1:10 000) or bipolar or argon plasma coagulation (Figure 40.9) or application of an endo‐clip.