General Considerations

Many epithelial tumors of the gastrointestinal tract develop as benign polyps before becoming malignant, as discussed in detail in earlier chapters of this book. These may be symptomatic or asymptomatic, pedunculated or sessile, and range in size from millimeters to many centimeters in diameter. If confined to the mucosa or superficial submucosa, they are nearly all amenable to endoscopic removal by one of a variety of polypectomy techniques, endoscopic mucosal resection (EMR), or endoscopic submucosal dissection (ESD).

The principles of endoscopic polypectomy have evolved to a standardized set of techniques since their introduction almost 40 years ago. EMR and ESD techniques continue to be developed as more recent innovations. Endoscopic resection aims to remove a tumor in its entirety for cure, for complete pathologic assessment, and to reduce or eradicate the risk of recurrence while maintaining the integrity of the wall of the gastrointestinal tract and avoiding procedure-related morbidity. Bleeding is the most common complication of polypectomy, occurring in 0.3–6.0% of cases. Postpolypectomy hemorrhage can occur immediately (within 12 hours) or can be delayed (up to 30 days) and is more likely to occur with larger polyps, sessile polyps, and polyps with thick stalks. Perforation, the most feared complication of polypectomy, remains rare but relatively unchanged in incidence since the introduction of these techniques. Perforation occurs in 1–2 per 1000 cases and is more likely to occur with piecemeal polypectomy of sessile polyps, cecal polyps, and with ESD.

Polypectomy, EMR, and ESD can all be accomplished in the sedated patient as there are no pain receptors in the mucosa and submucosa. The muscularis propria and serosa together with the mesentery are capable of generating pain sensation caused by mechanical forces (eg, stretching) and the thermal effects of electrosurgery. A wide range of accessories is now available for endoscopic polypectomy and the last decade has also seen improvements in electrosurgical generators with respect to ease of use, safety, and efficacy. All endoscopists should be equipped to remove small- to medium-sized sessile polyps and nearly all pedunculated polyps in the colon. Larger sessile polyps (>2 cm in diameter), very large pedunculated polyps in the colon, and polyps of all types in the esophagus, stomach, duodenum, and small bowel require additional expertise and technology and are usually referred to centers with experience in these areas. Such tertiary referral has been demonstrated to be safe and effective and to avoid the risk of unnecessary surgery. It is also cost-effective.

Removal of polyps throughout the gastrointestinal tract requires appropriate access with an endoscope bearing an instrumentation channel diameter adequate to take standard accessories. Most of these will pass through a 2.8-mm channel but some may require 3.2 mm or greater. Accessories include biopsy forceps, snares, injection needles, combination devices marrying more than one function in a single instrument, hemostatic clips and loops, bipolar and multipolar probes, and EMR sets providing a spray catheter, injector needle, special snare, and transparent cap, which comes in many shapes and diameters. Accessories for ESD are not yet generally available in the United States. Most accessories designed for colonoscopy will also be long enough for some enteroscopes when therapy in the small bowel is being planned.

Special stains for surface chromoendoscopy (eg, indigo carmine, Lugol iodine, methylene blue, and cresyl violet) may be needed prior to resection in order to optimize visualization of a polyp and its margins. Normal saline is the most common fluid used for submucosal injection during EMR or ESD. Epinephrine can be added to augment immediate hemostasis and methylene blue can be added to enhance visualization. Some experts prefer to inject a fluid of higher viscosity (eg, hyaluronic acid or glycerol), which dissipates less rapidly during resection allowing for a more sustained submucosal cushion during difficult polypectomy. Many endoscopes are capable of imaging with restricted wavelengths of light (eg, narrow-band imaging or multiband imaging), which allows visualization of morphology and vasculature in the submucosa, enhancing the endoscopist’s ability to recognize the edges of polyps and any malignant features. Marking agents, which are prefilled vials of a sterile suspension of very fine carbon particles (Spot; GI Supply, Camp Hill, PA); can be used for permanent documentation of a tumor resection site for future endoscopic or surgical reference. With the increasing use of laparoscopic colorectal surgery and the fact that up to 14% of endoscopically identified tumors can be incorrectly localized, endoscopic tattoo marking is essential for subsequent identification.

Many electrosurgical generators are manufactured specifically for endoscopic applications. Most incorporate computer-controlled outputs modified by feedback through the accessory to achieve the desired tissue effect with the least power necessary. They also incorporate menus for specific endoscopic procedures with defaults set by the manufacturer. All endoscopists and assistants performing electrosurgery should have a thorough knowledge of monopolar high-frequency circuits and their properties in order to understand the safe principles of cutting and coagulation, and to troubleshoot any problems that occur during polypectomy. The concept of current density (power per unit area) is essential to comprehend because this is how snare polypectomy cuts and coagulates tissue as it is being mechanically cut by the closing snare. It is our practice to retain a module for argon plasma coagulation whenever large polyps are being removed as an adjunct for tissue ablation and superficial coagulation. Bowel preparation must be good to excellent both for visibility and to reduce the risk of ignition of bowel gases such as hydrogen and methane. All fluid must be removed from around the polyp to be resected in order to maximize the current density where it is desired at the point of resection.