Polypectomy, Endoscopic Mucosal Resection, and Tattooing in the Colon
Polypectomy, Endoscopic Mucosal Resection, and Tattooing in the Colon
Sarah K. McGill, MD
Theodore W. James, MD
Ian S. Grimm, MD
Colonoscopy and removal of neoplasms prevents colorectal cancer. Techniques employed for resection include (1) cold snare polypectomy, (2) hot snare polypectomy, and (3) endoscopic mucosal resection. Recent research has provided a sound basis for choosing one method of polyp resection over another, based on polyp size and morphology. Endoscopic tattooing indelibly marks a lesion, facilitating localization for surgical resection or endoscopic surveillance.
Carefully assess the size, shape, and probable histology of a polyp prior to resection. Estimate the polyp’s size by comparing it to a device placed adjacent to the lesion, such as a standard snare catheter (2 mm), an open biopsy forceps (7 mm), or an opened snare of known diameter.
Polyp morphology can be described using the Paris classification: sessile polyps have a broad base (Paris 1s), pedunculated polyps have a narrow stalk consisting of normal tissue (Paris 1p), and nonpolypoid neoplasms are either slightly elevated but <2.5 mm in height (0-IIa), completely flat (0-IIb), or slightly depressed (0-IIc).
Study the color, surface pit pattern, and vascular pattern of a polyp to predict its most likely histology and the likelihood that it contains an invasive cancer. Advanced imaging techniques such as narrow band imaging (NBI) or i-Scan may help. The NBI International Colorectal Endoscopic (NICE) Classification is a simple and effective tool for visual prediction of polyp histology (Table 22.1).
TABLE 22.1 NICE Classification of Polyps
Same or lighter than background
Browner relative to background (verify that color arises from vessels)
Brown to dark brown relative to background; sometimes patchy whiter areas
None, or isolated lacy vessels may be present coursing across the lesion
Brown vessels surrounding white structures
Has area(s) of disrupted or missing vessels
Dark or white spots of uniform size, or homogeneous absence of pattern
Oval, tubular, or branched white structures surrounded by brown vessels
Amorphous or absent surface pattern
Most likely pathology
Hyperplastic or sessile serrated polyp
Deep submucosal invasive cancer
1. Cold snare polypectomy: most polyps <10 mm in diameter.
2. Hot snare polypectomy: pedunculated polyps; sessile polyps 6 to 19 mm.
3. Endoscopic mucosal resection (EMR): en bloc resection of polyps 6 to 19 mm; piecemeal resection of lesions > 20 mm (see Video 22.1).
a. Remove polyps encountered during screening colonoscopy at the time of their discovery, except for diminutive and small lesions with clear NICE 1 features that are located in the rectosigmoid colon. These hyperplastic polyps have no risk of progression to cancer.
b. Polyps that have a high probability of deeply invasive cancer should NOT be removed endoscopically. Instead, the most concerning areas of the polyp (e.g., NICE 3 surface pattern, depressed areas, ulceration) should be biopsied. If invasive cancer is confirmed, refer the patient for surgical resection.
c. Benign-appearing polyps too difficult to remove at the index colonoscopy should be photographed, with their location carefully documented, and in most cases, referred to an expert in advanced endoscopic mucosal resection. Partial colectomy for benign polyps is associated with greater risks and costs than endoscopic management, and is rarely necessary.
d. Nongranular laterally spreading tumor lesions with central depression that do NOT have NICE 3 features are considered ideal candidates for endoscopic submucosal dissection (ESD), an advanced technique performed at selected referral centers. Lesions with a high suspicion of superficial cancer invasion should be removed en bloc, either using EMR, ESD, or surgery.
1. The lesion has features suggestive of invasive carcinoma including ulceration, fixation, hard consistency, NICE 3 features. A nonlifting sign following submucosal injection is a relative contraindication; polyps that have been previously subjected to endoscopic therapy will often not lift well, but this should not be taken as a sign of invasive cancer.
2. Inability to complete the resection at the initial colonoscopy. Partial resection of a polyp should not be performed; the resulting submucosal fibrosis can complicate subsequent attempts at resection. Patients found to have large polyps during a screening examination may need to be rescheduled for a repeat procedure when adequate time and an experienced team are available to complete the resection in a single session.
3. Complete resection is not likely to be achieved. Polyps over 4 cm and those involving the ileocecal valve, appendiceal orifice, or anorectal junction are often very challenging, and may require referral to an expert in endoscopic resection techniques.
4. Unaddressed coagulation disorder.
5. Poor bowel preparation.
6. Poor general medical condition of the patient; excessive anesthetic risk.
7. Lack of the necessary staffing, training, and equipment needed to manage potential adverse events.
Colonoscopic polypectomy is routinely performed on an outpatient basis following standard bowel preparation. Include polypectomy as part of the typical consent for colonoscopy. Consider asking patients to discontinue aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), and anticoagulants, especially when they are known in advance to have a large polyp requiring resection.
4. Grounding pad, applied to the patient’s flank. Avoid placing the pad over large bones such as the femur or pelvis.
5. Polypectomy snares in a range of sizes.
6. Retrieval apparatus (e.g., specimen container in circuit with suction line for small polyps that are aspirated through the accessory channel; grasping devices and nets for retrieval of larger lesions).
7. Hemostasis devices for postpolypectomy bleeding, such as clips and bipolar electrocautery probes.
Adjuncts for EMR
1. Standard sclerotherapy injection needle.
2. Submucosal injectate. Options include normal saline solution, hydroxyethyl starch, sodium hyaluronate, glycerol, or succinylated gelatin. Availability of these agents varies by region. Mix the fluid with methylene blue or indigo carmine to obtain a sky blue color. Commercial products specifically designed for submucosal injection are available in preloaded syringes (Orise, Boston Scientific; Eleview, Olympus). Dilute epinephrine may be added to reduce intraprocedural bleeding, at a final concentration of 1:100,000 or 1:200,000.
1. Injection needle.
2. Tattooing agent: sterile carbon particle suspension (Spot, GI Supply, Camp Hill, PA).
Principles of Performing Effective Polypectomy, Regardless of the Modality Employed
1. Prior to beginning a resection, take the time to find a straight, relaxed scope position. Remove any loops using scope withdrawal and torque. This will greatly improve maneuverability.
2. Rotate the colonoscope until the polyp is located at the 5-o’clock position. Working on a polyp located in the upper half of the visual field is often inefficient or ineffective, because therapeutic devices exit the working channel of the scope at the bottom of the visual field.
3. Examine the full extent of the lesion. This will sometimes require retroflexion proximal to the lesion. For serrated polyps, electronic chromoendoscopy is often helpful in demarcating the edges of the lesion.
4. Stabilize the scope by anchoring it against the gurney with your hip, or by grasping the shaft of the scope between the fourth and fifth digits of your left hand.
5. Work close to the lesion. Place the snare accurately, to include a 1 to 2 mm margin of normal tissue beyond the edge of the polyp.
6. Following the polypectomy, carefully examine the base and perimeter of the resection defect for possible remnants.
Cold Snare Polypectomy
Cold snare polypectomy (CSP) is the preferred technique for resecting diminutive polyps (1 to 5 mm) and is also effective for removing small polyps (6 to 9 mm), most of which are also benign on histopathology. Cold snare polypectomy should be the dominant technique in screening examinations because thermal adverse events such as postpolypectomy bleeding and perforation are largely eliminated. Self-limited bleeding is commonly observed following cold snare polypectomy, but this is of no clinical consequence.
A key to successful cold snare polypectomy is to include a 2 to 3 mm margin of normal tissue surrounding the polyp, to avoid leaving any residual (Video 22.2). This requires use of a small, stiff snare, with a thin monofilament wire—ideally a device designed specifically for CSP. An en bloc cold polypectomy can be envisioned as a “fried egg”—the white portion representing normal tissue, and the yolk the polyp itself.