Complicated Polypectomy

Abstract

One of the major advances in medicine during the last 50 years has been the colonoscopic removal of colon polyps, which has decreased the incidence, morbidity, and mortality of colorectal cancer. Most polyps in the large bowel are less than 1 cm in diameter, a size that has enabled successful treatment of polyps and has permitted the relatively easy removal of polyps throughout the world. Only 20% of polyps are over 1 cm in size, with most large polyps (over 20 mm) being adenomas.The removal of colon polyps requires the ability to transect a polyp, while simultaneously preventing bleeding and maintaining the integrity of the colon wall during use of electrothermal current. The successful removal of colon polyps by the snare and cautery technique involves a balance between the act of transection and the hemostasis that is required. During removal of large polyps, the two forces that must be balanced are the shearing force from closing the wire loop and the thermal energy, which results in cauterization of blood vessels providing hemostasis. Both the shearing force and hemostasis must be achieved simultaneously to permit removal of polyps without bleeding and with the safe application of thermal energy to the thin colon wall without a deep zone of thermal destruction. The closure of the snare can result in cutting through a polyp but guillotine of a polyp can often be associated with bleeding; the application of thermal energy alone through the wire loop without a shearing force will cause deep thermal injury without the ability to sever a polyp. It is important that both forces, shearing and application of heat, must be used simultaneously. Small polyps, up to 5 mm in diameter, have small nutrient blood vessels and are often successfully removed by "cold" snare transection (without the application of thermal energy) with no significant bleeding. 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 to occlude the vascular channel prior to heat sealing it 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 intestinal tract. In a bleeding gastric ulcer, for example, hemostasis is usually achieved by pushing on a vessel with a probe (BICAP or heater probe) and then applying heat which obliterates the vascular channel. During polypectomy, once the blood vessel walls have been coapted by squeezing the snare, permanent hemostasis is achieved by employing thermal energy, which seals the coapted blood vessel through which blood is no longer flowing. This is effective for pedunculated polyps that have a single arterial supply as well as for sessile polyps where several smaller vascular channels exist. The electrosurgical unitIt is important for the succ...