“ER” is the general term for the different resection techniques used to treat neoplastic and uncertain lesions in the gastrointestinal tract. The term “endoscopic mucosal resection” is widely used; however, it is misleading because significant proportions of the submucosal layer are also resected, which is important in the case of submucosal infiltration of the tumor.
Endoscopic Resection with a Ligation Device
A common method is ER with a ligation device, also used for ligation of esophageal varices. With this method, the target lesion (Fig. 173-1A) is sucked into the cylinder of the ligation device (Fig. 173-1B) and a rubber band is then released to create a pseudopolyp that has the rubber band at its base (Fig. 173-1C). After this, the pseudopolyp is resected with a reusable snare underneath the rubber band to achieve larger resection specimens (Fig. 173-1D).
Endoscopic resection with a ligation device.
Several ligation devices are available: single-use devices, multiple usable ligators or ligation devices with multiple rubber bands. Another useful development is a ligation cylinder that has six rubber bands and a facility for advancing a snare through the working channel of a regular endoscope. This enables the endoscopist to perform up to six resections without the necessity of withdrawing and reintroducing the endoscope. This device is widely used for piecemeal resection of larger neoplastic lesions.
Endoscopic Resection with a Transparent Cap
The cap technique was introduced by Inoue and Endo12 almost 20 years ago. When ER is performed with the cap technique, a specially developed transparent plastic cap is attached to the end of the endoscope. After submucosal injection under the target lesion, usually with a saline-epinephrine solution, the lesion is sucked into the cap and resected with a diathermy snare that has previously been loaded onto a specially designed groove on the lower edge of the cap. Marking the borders of the lesion either with electrocautery using the tip of the snare or an APC probe is recommended before performing the resection, because injecting underneath a discrete neoplastic lesion often makes it difficult to identify the borders of the target lesion afterward.
Ulcerated lesions often have fibrosis, which attaches the submucosa to the lamina muscularis propria, resulting in failure of the lesion to lift as is frequently found in tumors with submucosal infiltration. In these cases, ER is not advisable, or should only be performed with caution. Larger lesions can usually be resected completely with the piecemeal technique, but this method seems to be associated with a higher recurrence rate.
Endoscopic Submucosal Dissection
The endoscopic submucosal dissection (ESD) procedure in the treatment of early gastric cancer was first described by Hosokawa and Yoshida13 and Ono et al.14 They used an insulated-tip knife to obtain a large resection specimen with the neoplasm resected en bloc (Fig. 173-2E). Once the borders of the neoplastic lesion have been adequately visualized, the borders are marked with electrocautery at a distance of 5 to 10 mm from the margin of the carcinoma (Fig. 173-2A). Then submucosal injection of fluid is performed to elevate the lesion from the muscular layer, and the mucosa surrounding the lesion is circumferentially cut outside the markings. Finally, the submucosal connective tissue is dissected with a dedicated knife (Fig. 173-2B). Visible vessels can be coagulated with the top of the knife or a coagulation forceps to prevent bleeding (Fig. 173-2C and D). The fluid used for submucosal injection could be isotonic saline solution or a solution of hyaluronic acid with additives including a dye, such as indigocarmine; a composition defined by the individual endoscopist. A wide variety of different knives are used for ESD, including the insulated-tip knife, Hook knife, flex knife, needle knife, triangle-tip knife, flush knife, and hybrid knife. With the flush and hybrid knife, submucosal injection and dissection can be performed at the same time without changing the instruments. The size of the resected specimen obtained with ESD can extend up to more than 10 cm in diameter. Because of the high complication rate in inexperienced endoscopists, practice with ESD models is highly recommended to become familiar with this technique. Afterward, ESD procedures should be carried out in the stomach, then in the rectum, before this method is used for esophageal lesions. ESD is a demanding, time-consuming technique with a flat learning curve.
Endoscopic submucosal dissection.