Introduction

Through opposite trends of invasiveness, gastrointestinal (GI) endoscopy and laparoscopic surgery have converged to produce an intriguing but still largely experimental field termed natural orifice transluminal endoscopic surgery (NOTES). Since the publication in 2004 by Kalloo and colleagues¹ on transgastric peritoneoscopy in the porcine model, NOTES continues to develop as a minimally invasive, “scar-less” technique for intraperitoneal and more recently intrathoracic surgeries. The theoretical advantages of NOTES include cosmesis; decreased anesthesia time; shortened postoperative recovery; and elimination of postsurgical complications associated with transabdominal and transthoracic incisions, such as skin infections, wound dehiscence, and hernias. Early questionnaire studies indicated that patients would prefer a NOTES approach over a traditional laparoscopic approach primarily because of issues surrounding pain and visible scars.²

The definition of the NOTES concept is in flux and currently spans a continuum. Initially, the concept referred to surgeries performed purely via a natural orifice; and these procedures are referred to in this chapter as pure NOTES. More recently, the concept of hybrid NOTES has evolved to allow for concomitant assistance provided by laparoscopy as a bridge to pure NOTES. In addition, the concept of NOTES now also encompasses single-incision laparoscopic surgery (SILS) (i.e., single-port laparoscopy or transumbilical laparoscopy), which technically is not surgery via an orifice but rather the coalescing of several laparoscopic ports into a single multilumen transabdominal trocar accommodating rigid laparoscopic instruments.

Moving forward, how might gastroenterologists fit within the broad and shifting NOTES landscape? Which NOTES procedures might become realistic procedures for GI endoscopists? An analysis of the published literature provides clues to factors that may influence the answer.

Current State of Natural Orifice Transluminal Endoscopic Surgery (NOTES) Research

Since the first NOTES publication by Kalloo and colleagues in 2004,¹ there has been progress toward human NOTES in numerous international centers but only a handful of U.S. centers. As of July 2009, the Natural Orifice Surgery Consortium for Assessment and Research NOTES registry had 166 human cases from eight U.S. sites and two international sites, 162 of which were approved by an institutional review board.³ SILS cases were not included in this registry. Most of these natural orifice cases were performed via the transvaginal route because of the historical precedent of culdoscopy performed by gynecologists, a reduced concern regarding sterility, and a decreased need for “secure” closure of the posterior fornix access point compared with enteral closure. Most of these cases also required laparoscopic assistance and would be more accurately categorized as hybrid NOTES procedures. Of the few pure NOTES procedures, Swanstrom and coworkers⁴ succeeded in performing transgastric cholecystectomy. Other pure NOTES procedures on closer examination have been hybrid transgastric procedures. There have been two small published case series of transgastric cholecystectomies assisted by the use of one to three transabdominal trocars.^5,6 There has also been a series of 10 diagnostic transgastric peritoneoscopies performed after laparoscopic exploration before Whipple’s surgery,⁷ but the challenge of access closure was not directly addressed. Generally, most pure NOTES publications to date have been animal and human cadaveric studies.

Of the eight fundamental obstacles to NOTES identified in the original 2005 White Paper (Box 54.1),⁸ the most challenging obstacles to pure NOTES human studies have been the ones heavily dependent on device development.⁹ Two specific areas of technical need are highlighted here. First, current closure devices remain in various stages of development with none emerging as the clear favorite. Viscerotomy closure must be 100% secure and ideally be easy to perform and reproducible for any chance of clinical adoption of NOTES. No device has yet fulfilled all of these requirements. The second and probably the most rate-limiting step in the clinical adoption of NOTES is the commercial development of a robust, flexible, versatile multitasking platform. Complex surgical maneuvers, even in surgeries as commonplace as cholecystectomies, have technical requirements that cannot be met by a double-channel endoscope, such as triangulation of instruments, aggressive traction and countertraction of tissue, position fixation, and reliable force transmission over instruments. The NOTES platform should be versatile enough to manage iatrogenic intraperitoneal complications, such as hemorrhage, perforation, or organ injury. It is not surprising that there has been such a preponderance of hybrid NOTES studies and a general tendency to retain the laparoscopic paradigm insofar as SILS is concerned.

Future Indications for the Gastroenterologist

Despite the many limitations on the translation of NOTES from animal and cadaveric studies to actual human trials, endoluminal GI endoscopy has steadily grown bolder in procedures involving and sometimes traversing the gut wall in ways not heretofore considered as NOTES per se. Endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) have naturally evolved to attempts at endoscopic full-thickness resection (EFTR) for early GI cancers. Endoscopic treatment of pancreatic disease has expanded from endoluminal treatment of the pancreatic duct (endoscopic retrograde pancreaticocholangiography [ERPC]) to transgastric or transduodenal needle puncture for sampling of pancreatic lesions (endoscopic ultrasound [EUS]–guided fine-needle aspiration) and for endoscopic pseudocyst drainage. Transgastric retroperitoneal necrosectomies have also been increasingly performed.

This chapter elaborates on five areas we believe are potential NOTES procedures that will be performed by gastroenterologists in the future (Box 54.2). These procedures share one or more of the following characteristics: (1) surgical sites more easily reached using a flexible endoscope or flexible NOTES platform compared with a laparoscope or via open access, (2) surgical procedures of low to medium complexity, and (3) probable improved outcomes from adjunct use of EUS for access or directed biopsies or resections.

Endoscopic Full-Thickness Resection

EFTR represents the next step in the natural evolution of endoscopic procedures aimed at removing GI cancers and cancerous precursor lesions. EFTR follows in the line of polypectomy, EMR, and ESD. For early stage gastric cancers, ESD cures certain T1, N0 adenocarcinomas. EFTR may find a role in the treatment of T2, N0 adenocarcinoma and small GI stromal tumors.¹⁰ In 2006, Kaehler and associates¹¹ reported EFTR in two patients (one with early gastric cancer and the other with carcinoid tumor) using a flexible stapler. There have been other case reports of gastric and duodenal EFTR but with laparoscopic assistance.^12,13 In these cases, resection was performed endoscopically, but closure was performed laparoscopically. A full-thickness suturing device has been used to close comparably smaller gastric defects during or after EMR of gastric tumors¹⁴ and a perforation resulting from GI stromal tumor resection using ESD.¹⁵

Although experience of EFTR in other organs has been reported mostly in animal studies, human studies are likely to be performed in the near future. Successful EFTR has been reported in an animal survival study.¹⁶ Colonic full-thickness resection has also been successfully shown in the animal model using various closure strategies, including but not limited to T-tags,¹⁷ clips,¹⁸ nitinol compression clamps,¹⁹ and staplers.²⁰

Diagnostic Peritoneoscopy and Lymph Node Harvesting

NOTES peritoneoscopy with lymph node harvesting has potential as a minimally invasive and accurate means of intraabdominal cancer staging. In patients in whom operability is uncertain, NOTES peritoneoscopy and lymph node mapping may be preferable to staging laparoscopy. In pancreatic, biliary, or gynecologic cancers, transgastric peritoneoscopy could be used to assess quickly for peritoneal and liver implants.²¹