Laying the foundation for NOTES: another brick in the wall
Article Outline
Abbreviation: NOTES, natural orifice transluminal endoscopic surgery
Few topics in GI therapy in the past decade have engendered as much excitement and controversy as natural orifice transluminal endoscopic surgery (NOTES). This term was coined in 2005 by leaders from the American Society for Gastrointestinal Endoscopy (ASGE) and the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES), who realized that the potential existed to expand the capabilities of therapeutic endoscopy to perform intraperitoneal surgery. The group was acutely aware of the damage that had occurred during the introduction of laparoscopic cholecystectomy and sought to get ahead of the curve for NOTES. This group, the SAGES/ASGE Joint Committee, attempted to prospectively manage the introduction of what was viewed at the time as a potentially disruptive technology. A white paper was written that outlined the fundamental challenges that needed to be addressed before NOTES would be ready for prime time1 and also insisted that human studies be done under appropriate institutional review board supervision.
Today, much of the excitement surrounding the report by Rao et al2 of the first transgastric appendectomy has dissipated. I am often told by my colleagues that NOTES is dead because, although the idea of surgery without scars was sexy, it was an empty promise all along, based on a nonphysiologic approach and unethical principles. However nothing could be further from the truth. Through the SAGES/ASGE Joint Committee and the Natural Orifice Surgery Consortium for Assessment and Research, a community of like-minded interventional gastroenterologists and surgeons has coalesced to investigate the fundamental questions of feasibility and utility of transluminal intracavitary surgery. Natural Orifice Surgery Consortium for Assessment and Research has raised and distributed nearly $4 million to fund research, had held 4 annual meetings, and is about to launch a U.S. multicenter prospective, randomized trial to evaluate NOTES cholecystectomy. When one actually looks back to the white paper and what its authors were thinking in 2005, it seems that things are actually going according to plan. In 2005, the concept of NOTES seemed revolutionary, but as we follow the road map, the actual implementation of these ideas in clinical practice is clearly going to be evolutionary.
One of the fundamental challenges in the white paper was to manage intraperitoneal complications. Certainly bleeding, even if minor, occurs in most surgical procedures, so the ability to achieve and maintain hemostasis is a critical capability for NOTES to develop beyond diagnostic use. In this month's issue of Gastrointestinal Endoscopy, Park et al3 conclusively demonstrate the effectiveness of a flexible bipolar forceps to control hemorrhage. Surgeons have relied increasingly on energy devices that bloodlessly seal and divide tissue, but to date, these devices have not been adapted for delivery via a flexible endoscope. In the Park et al study, the flexible bipolar forceps device sealed vessels up to 6 mm rapidly and reliably. This capability may enable clinicians to divide mesenteric vessels as well as the vast majority of human intraperitoneal visceral vessels.
For the past 5 years, investigators in the NOTES arena have approached device makers with wish lists for instruments that at a minimum have presented complex engineering challenges and occasionally would have required defying the laws of physics. Furthermore, the deliberate pace of the development of NOTES as well as scrutiny by regulatory agencies has led many companies initially interested in NOTES to focus their research and development efforts on single-port access surgery where a market can be developed more rapidly and commercial success is more immediate. Perhaps devices developed for this type of surgery will be useful for NOTES, but thus far most single-port-access surgery and the devices used to perform it are remarkably similar to traditional laparoscopic surgery. Therefore, the significance of the Park et al report should not be overlooked. Suddenly the possibility of performing lymphadenectomies, bowel resections, and resection of solid organs by using a flexible operative platform is a major step closer to reality. So what else do we need before we have a toolkit or platform that we are comfortable with to perform NOTES?
First and foremost, we must open our minds and acknowledge that transgastric access to the peritoneal cavity, as originally described by Kalloo et al,4 is but one of many access routes for NOTES. Although a flexible endoscope is ideal for transgastric access, particularly if working in the pelvis, it may not be optimal for transvaginal surgery. In Germany, the vast majority of transvaginal cholecystectomies have been performed with a rigid laparoscope, and the results seem to be excellent.5 Although purists might claim that this is not NOTES, it is hard to deny that these patients had procedures that were fundamentally the same as what many North American and Latin American groups call a hybrid NOTES cholecystectomy. Recently, the first NOTES transanal rectosigmoid resection for cancer in a human was performed by using a rigid platform (transanal endoscopic microsurgery). In addition to these traditionally based methods of providing visualization and access, there is growing consensus among investigators that separating visualization from instruments that dissect, retract, and repair tissues is beneficial. It is very likely that in the near future, miniature cameras will be deployed through the transvisceral access route and then controlled wirelessly. This will free up real estate in the access site as well as facilitate visualization and hence improve triangulation.
Early on in the NOTES experience, investigators realized the need for a stable operative platform once access had been achieved. There still will be many situations in which a flexible endoscope remains the cornerstone of a NOTES platform. Flexibility is a key asset in traversing the body's natural orifices but becomes a liability when trying to retract tissue or work against the pull of gravity. Therefore, flexible devices that can be stiffened or locked in place to provide stability (as well as easy exchange of instruments) are likely to be another key component of NOTES platforms. A variety of these types of devices will soon be available.
To perform delicate dissection as well as precise reconstruction of tissues, clinicians will need to have better dexterity. Flexible suturing devices are close to market, whereas flexible staplers seem a bit farther away. We still need integrated platforms that add dexterity to enable suturing and careful tissue dissection. Some of the early prototypes have been complex marvels of modern engineering that are too expensive and complex for large-scale production at a sensible cost. Many assume that robotics will be an integral part of the solution, but, at present, cost constraints are also likely to make current systems unattractive. Nevertheless, in the field of microrobotics, exciting work is ongoing. Lehman et al6 developed microrobots that can be introduced through a single-access port and controlled remotely to perform porcine cholecystectomies. Efforts are also under way to develop self-assembling robots in Europe that would be more robust and larger than a remotely controlled robot whose size was limited by the diameter of the access route. Several innovative and relatively simple mechanical systems designed for single-port access surgery will be introduced next year and may ultimately be adaptable for NOTES. Until one of these enabling technologies matures, NOTES will probably not be able to match similar laparoscopic procedures for cases requiring a lot of suturing or dissection.
As currently practiced, nearly all NOTES procedures require some type of percutaneous assistance. This is most commonly because of the need to provide robust tissue retraction. Some novel mechanical solutions now exist using hooks to attach tissue and organs to the parietal peritoneum, and in the future, it seems likely that magnets may be useful as well. This type of “out-of-the-box” thinking will be essential if NOTES is to develop beyond a laparoscopy-based paradigm. Venturing into new territory like this or like remotely controlled mini-cameras that are decoupled from scopes is exciting. However, it is often a long journey from proof of concept to clinical success.
Since the white paper was published, NOTES has come a long way. More than 1000 cholecystectomies and a variety of other hybrid procedures have been performed. Ongoing device development is necessary but not sufficient for the field to progress. The work by Park et al is an important step along the way, but creativity and imaginative solutions will be essential if NOTES is to be more than just a passing fancy. Surgery without scars is indeed possible. NOTES will eventually become mainstream, but we must be patient and allow the evolutionary process to continue.
Disclosure
The author disclosed the following financial relationship relevant to this publication: Honorarium from Olympus.
References
- . The ASGE/SAGES Working Group on Natural Orifice Trans-lumenal Endoscopic Surgery (October 2005). Surg Endosc. 2006;20:329–333
- . NOTES: human experience. Gastrointest Endosc Clin N Am. 2008;18:361–370
- A randomized comparison of a new flexible bipolar hemostasis forceps designed principally for NOTES versus a conventional surgical laparoscopic bipolar forceps for intra-abdominal vessel sealing in a porcine model. Gastrointest Endosc. 2010;71:835–841
- Flexible transgastric peritoneoscopy: a novel approach to diagnostic and therapeutic interventions in the peritoneal cavity. Gastrointest Endosc. 2004;60:114–117
- Scarless cholecystectomy with combined transvaginal and transumbilical approach in a series of 20 patients. Surg Endosc. 2008;22:1427–1429
- Natural orifice cholecystectomy using a miniature robot. Surg Endosc. 2009;23:260–266
PII: S0016-5107(09)02938-1
doi:10.1016/j.gie.2009.12.034
© 2010 American Society for Gastrointestinal Endoscopy. Published by Elsevier Inc. All rights reserved.
