© Springer International Publishing AG 2017Kevin M. Reavis (ed.)Per Oral Endoscopic Myotomy (POEM)10.1007/978-3-319-50051-5_1
1. Introduction: Endoscopic Submucosal Dissection to Per Oral Endoscopic Myotomy (POEM)
Department of Surgery, MetroHealth Medical Center, 2500 MetroHealth Drive, Cleveland, OH 44109-1998, USA
Digestive Disease Center, Showa University Koto-Toyosu Hospital, Toyosu 5-1-38, Koto-ku, Tokyo 135-8577, Japan
The development of Per Oral Endoscopic Myotomy (POEM) for esophageal achalasia is, in large part, the result of large-population screening for GI malignancy. While screening for colorectal cancer in average-risk patients over the age of 50 is well-accepted in America, there is no equivalent screening protocol to address esophageal or gastric cancer. In Japan, on the other hand, the rates of both gastric adenocarcinoma and squamous carcinoma of the esophagus are much higher than those observed in Western countries. As a result, screening upper endoscopy is not only more widespread, but also more sophisticated, involving adjuncts such as chromoendoscopy, narrow band imaging, magnification endoscopy, and more recently endocytoscopy. A large number of lesions are detected (the National Cancer Center in Tokyo alone treats more than 10,000 gastric lesions per year) and some form of resection is recommended for the vast majority. This is partly the result of differences in the pathologic interpretation between Japanese and Western pathologists (a lesion with “high grade dysplasia” or “carcinoma in situ” in the West may be considered “cancer” in Japan). Based on the observation that early lesions have a very low rate of lymph node metastasis, local resection is often preferable to surgery and a number of endoscopic techniques have evolved for this purpose.
This chapter will trace the development of the POEM procedure from its roots in the endoscopic resection of esophageal and gastric lesions. We will follow the progression of the technical components, from simple colorectal polypectomy to en bloc resection of “strips” of tissue, and finally to dissection of the submucosal space and submucosal tunneling. We will also examine the evolution of the equipment necessary for the procedure, including the creation of distal caps and the development of specialized knives.
Endoscopic Mucosal Resection (EMR)
In 1955, two years before the development of the fiberoptic endoscope, Rosenberg reported the “saline lift” technique, in which he injected saline into the submucosal space to increase the distance between the mucosa and the muscle layer, thereby reducing the risk of perforation during polypectomy in the rectum and distal colon [1, 2]. In Germany, Deyhle et al. developed a similar technique for the resection of sessile colon polyps in 1973, and they reported the first true en bloc EMR of a small gastric lesion using a wire snare in 1974 [3–5]. In Japan, Tada et al. also applied the saline lift to the resection of early gastric lesions. They utilized submucosal saline injection followed by resection of the mucosal bleb with a wire snare. Their technique was initially published in Japanese in 1984, and ultimately they published a large series in English in 1993 .
An alternate technique, dubbed the “lift and cut biopsy,” was originally described by Martin et al. in 1976 . Rather than pushing the mucosa away from the muscle layer with saline, they utilized a double-snare technique, using one snare to grasp and elevate the mucosa, and the other snare to resect the specimen. Takekoshi et al. applied this to early gastric cancer in Japan beginning in 1978 . They used a grasper to elevate the mucosa and an electrocautery wire snare to resect the lesion. In their series of 308 lesions over 15 years, they noted that the size, depth, location, and differentiation of the lesion affected their ability to completely excise lesions. The rates of incomplete resection were as high as 57% for undifferentiated carcinomas, lesions larger than 1–2 cm, and lesions on the anterior or posterior wall. The technique was most useful for small, well-differentiated lesions on the lesser curve.
The original “strip biopsy” merged the “saline lift” with the “lift and cut biopsy,” beginning with a submucosal saline injection, then elevating the mucosa with a grasper, and finally resecting the specimen with a wire snare.
Publications in Japanese by Masuda et al. in 1993 and in English by Chaves et al. in 1994 reported use of a variceal ligating device, similar to the technique of Van Stiegmann, in which flat lesions were converted into “polyps” by grasping tissue and strangulating it at the base with a ligating band [11, 12]. The “polyp” could then be resected in the usual fashion with a wire electrocautery snare. The technique eventually became known as the “EMR-L.” While beginning in the colon, EMR-L was applied to lesions of the esophagus by Fleischer et al. who published their series in 1996 .
Evolution of the Distal Cap
Inoue and Endo modified the “lift and cut biopsy,” adding a transparent overtube to improve their ability to control and resect esophageal mucosa by grasping and snaring. In 1990, they reported a series of 11 cases, including resection of a small focus of adenocarcinoma in a short segment of Barrett’s esophagus, and they found that it was possible to resect both large and near-circumferential segments of mucosa in piecemeal fashion, leaving the underlying muscle layer intact .
Makuuchi developed a special overtube, which he combined with submucosal saline injection, suction (rather than grasping), and snaring to resect larger fragments of esophageal mucosa than had previously been possible . Kawano et al. modified the so-called “Makuuchi tube” to include a lateral window, which served as a mucosal trap . The main limitation of the tube technique, however, was that it could only be applied to lesions of the esophagus.
To address the shortcomings of the transparent overtube, Inoue et al. developed a transparent plastic cap that attached to the distal tip of the endoscope in 1992 and published their initial series in 1993, calling their technique the “EMR-C” . A refinement published by Inoue et al. in 1994 added a small ridge to allow for easy seating of the snare at the distal end of the cap . The basic idea of grasping, strangulating, and resecting tissue was the same as with EMR-L, but the EMR-C procedure combined strangulation and resection into a single step. The technique was applied to a series of colonic lesions published by Tada et al. in 1996 and to resection of the duodenal ampulla by Izumi et al. in 1998 [19, 20]. In effect, the EMR cap served as a portable tube that traveled with the endoscope and allowed for the injection, suction, and snare technique to be applied to lesions anywhere in the gastrointestinal tract that could be reached with the endoscope.
The main complication associated with both the EMR-L and EMR-C techniques is involvement of the muscle layer within the resected specimen, causing full-thickness perforation. Anticipating this, early ex vivo pilot studies conducted in Japan involved resected surgical specimens, including human esophagus, stomach, and colon. EMR-C was performed at various locations and with various volumes of injected saline (ranging from 0 to 20 mL), while simultaneously examining the bowel wall under ultrasound guidance. The purpose at the time was to determine safety parameters regarding the size of the distal cap, volume of submucosal saline injection, strength of the suction, and ideal location within the bleb for placement of the wire snare; however, of particular interest is the finding that large-volume saline injection in the esophagus caused semi-circumferential submucosal dissection, creating a space of approximately 1 cm (the diameter of a standard gastroscope) between the mucosa and the muscle layer without any apparent disruption of the mucosa itself.
Endoscopic Submucosal Dissection (ESD)
From EMR to ESD
Beginning in 1982, Hirao et al. added a “pre-cutting” step to the original “strip biopsy.” They began with submucosal injection with a solution of hypertonic saline and epinephrine, and followed this by cutting the mucosa circumferentially around the lesion using a needle knife. In doing this, the intended specimen retracts, effectively increasing the size of the lesion that can safely be resected with the cutting snare. They utilized the technique in 106 patients with lesions of the stomach (n = 101) and esophagus (n = 5) and published their series in 1988 . The step of pre-cutting anticipated what would later become a critical step in ESD.
Hosokawa and Yoshida added a triangular plate protected by a ceramic tip to the end of a needle knife in 1995, developing the first insulated tip (IT) knife, which they published in Japanese in 1998. The following year, Gotoda et al. modified the “pre-cutting” technique of Hirao et al. using the IT knife rather than the needle knife to resect two rectosigmoid lesions . They felt that the IT knife was easy to use and that the insulated tip minimized the risk of perforation. The upper limit of lesions that could be resected with pre-cutting and snaring, however, remained approximately 3 cm.
The group of Yamamoto et al. developed a technique that utilized submucosal injection and pre-cutting, but did not require use of a snare. They used an insulated, single-tooth forceps attached to electrocautery that could both grasp and cut tissue, along with a modified transparent cap that was flat at the distal end to maintain the orientation of the forceps. An added benefit of the cap was to maintain visualization during retraction and dissection of the tissue. In 1998, they resected a 4 cm flat lesion in the rectum by injecting, pre-cutting circumferentially, and dividing the submucosal fibers under direct vision; and in 2000, they presented the en bloc resection of a 6 cm gastric lesion at the ASGE meeting in San Diego, CA [23, 24]. Further modifications included use of a tapered cylindrical (rather than flat) hood and a needle knife to more precisely control the location and depth of the electrocautery. In 2002, the group published a series of 70 cases using this refined technique .
Evolution of Knives
In 2004, Rösch et al. reported their initial experience using the IT knife (rather than the needle knife) in 37 patients with admittedly poor results, but as this modified en bloc form of EMR (eventually renamed ESD) became more popular, the equipment and procedural techniques evolved quickly .
Oyama et al. published a series in 2005 with improved rates of en bloc resection using a “hook knife” (initially reported in Japanese in 2002), which consisted of a right-angle modification of the needle knife . The knife could be rotated to the optimal direction and then used to hook and retract the tissue prior to cutting, resulting in improved precision and safety.
In 2004, Yahagi et al. reported (in Japanese) the use of a “flex knife.” Created from a twisted snare and a flexible sheath, the knife was soft and flexible with a bumper on the end to easily control the depth of incision, reducing the risk of disruption of the muscle layer. In the same year, Inoue et al. reported (also in Japanese) an ESD using the triangle-tipped (TT) knife, which essentially removed the ceramic tip from the IT knife, exposing the multidirectional triangular tip.