Once in a few decades in science or medicine, an idea emerges that is so powerful that it changes forever how we think about that field. Natural Orifices Translumenal Endoscopic Surgery (NOTES) has the potential to break the physical barrier between bodily trauma and surgery.
At the dawn of surgery, excellence was associated with big incisions: “big scar – big surgeon”.
In the 80s, minimally invasive surgery was born representing one of the greatest surgical evolutions of the 20th century. After Kalloo’s first report in 2004 on transgastric peritoneoscopy in a porcine model, the interest in natural orifice transluminal endoscopic surgery (NOTES) has blossomed. Theoretically the same operation performed laparoscopically could be carried out through natural orifices without any abdominal incision avoiding pain and scarring. The lesson learned from the advent of laparoscopic surgery, thought us that we could be witnessing the birth of another surgical revolution.
Since 2004 many abdominal procedures that use a NOTES approach have been successfully performed in animal models. However, the initial excitement for NOTES has been somewhat tempered by the reality that a NOTES procedure in human without laparoscopic assistance has not been performed by most groups. Indeed, a major issue is the lack of stable operative platform and flexible instruments that allow retraction and exposure of the organs, such as appendix or gallbladder. Will this issue change the future of NOTES?
Originally created as a diagnostic tool, flexible endoscopy has evolved over the past decade to become more therapeutic in nature. Several advanced therapeutic techniques have been reported, with many being incorporated into routine clinical practice over time, including endoscopic mucosal and submucosal dissection, endoscopic suturing for GERD, and, more recently, natural orifice transluminal endoscopic surgery (NOTES). This complex technique involves breaching the wall of the stomach, colon, or vagina by endoscopic means to gain access into the peritoneum to perform the desired therapy. There are a number of potential benefits to using NOTES over traditional surgical techniques that are associated with the lack of surface incision, including the elimination of surgical site infections and any visible scarring, a reduction in pain and the need for anesthesia and analgesia, recovery time, hernia formation and adhesions, and the ability to perform procedures in patients where an abdominal incision is difficult such as in the morbidly obese.
Few endoscopists in the past would have dared to breach the GI lumen on purpose. Percutaneous endoscopic gastrostomy was the first surgical endoscopic technique that intentionally perforated a hollow organ(1). Following this, transluminal drainage of post-pancreatitis collections progressively accustomed some endoscopists to an extra-luminal approach(2). The first to have used a surgical endoscopic technique for the resection of an organ’s segment, and as such an opening to the peritoneal cavity, is G. Buess, who described in 1984 transanal endoscopic surgery(3). Complete resections of low sigmoid or rectal tumours with parietal defect suturing are performed through an adapted rectoscope using specific instrumentation.
After Kalloo’s first report in 2004(1) on transgastric peritoneoscopy in a porcine model, the interest in NOTES has blossomed. This article sparked enthusiasm in the medical community but also in the surgical community. Theoretically the same operation performed laparoscopically could be carried out through natural orifices without any abdominal incision. The lesson learned from the advent of laparoscopic surgery, thought us that we could be witnessing the birth of another surgical revolution.
Although most believe after Kalloo’s report(1) that the peroral route will be the one to dominate NOTES in the future, today there are still several difficulties performing transgastric NOTES techniques with the instruments currently available, A factor limiting the transgastric route is the lack of a secure and reliable method for creating and closing the gastrotomy required by the procedure. Indeed, creating a gastrotomy from within the stomach requires a blind entry to the peritoneal cavity making it hard to both avoid damage to neighbouring structures(2) and ensure the gastrotomy is sited in the best possible position. The value of endoscopic ultrasonography to overcome these issues is under evaluation(3).
Several gastrotomy techniques have now been described. The most used technique is based on the established safety of percutaneous endoscopic gastrotomy (PEG) placement with ballon dilatation(4). A flexible wire passed through the anterior abdominal wall guides the stomach incision and dilatation of the gastrotomy. Another seductive approach is the submucosal flap technique. An incision is first made in the gastric mucosa. The submucosal space is developed and a tunnel of at least 5 cm length is created using a dissecting balloon(5) or EMR-cap(6). After tunneling away from the mucosal defect, the muscularis and serosa are punctured, and the abdomen is entered. At the end of the procedure, the scope is withdrawn, the myotomy site is sealed with the overlying mucosal flap, and only the mucosa is closed.
Closure of the gastrotomy is indeed crucial. Although in some early studies, the gastrotomy performed with baloon technique was left open, there is now general agreement that there must be near-zero tolerance for leaks. The ideal closure should be rapid, reproducible, and safe, ideally performed under vision to avoid any injury to the adjacent organs and should grant a full thickness bite. In addition a method that is easily reproducible and inexpensive is highly desirable. Different methods have been reported in the literature mainly presented from the endoscopist’s side with endoclips representing the most commonly used method of closure(7,8). However, the simple application of mucosal clips enables only a single-layer tissue approximation and is best suited for small defects and could be used in emergency situation to close an accidental minute endoscopic perforation.
Different techniques have been reported in the literature with variable results and success rates but majority of these at present remain experimental and are not widely available. Original techniques using a cardiac septal occluder(9), surgical stapler(10), transparietal tags(11), bioabsorbable plugs(12) were described. Using two endoscopes to provide layer-by-layer endoscopic clip closure is another alternative that uses current endoscopic instruments(13).
While secure closure of the gastric access site is critical and difficult, transvaginal access, a route well known to gynaecologists, de facto overcomes these problems. The experience by gynecologists performing transvaginal procedures has demonstrated safety also in regards to rarity of pelvic infection or injury of adjacent organs. In addition closure of the colpotomy is performed under vision using standard surgical techniques. Additional advantages are a straight shot when targeting organs in the upper abdominal quadrants and, the fact that the colpotomy allows the use of rigid laparoscopic instruments at the side of the scope that could assist in different steps of the procedure. The removal of surgical specimens through an incision of the posterior fornix is frequently performed after different laparoscopic procedures instead of using more morbid large incisions of the abdomen or flank as required previously.
Direct access to the access site is also an advantage of the transanal route. Transcolonic NOTES has been the least explored approach to the peritoneal cavity because of concerns related to faecal contamination and intra-abdominal infectious complications. The benefits of transcolonic access include in-line endoscopic visualization, the ability to create and close the colotomy with existing transanal endoscopic microsurgery (TEM) equipment, and suitability of both male and female patients.
The next question to be addressed is whether natural orifice access can be extended into other body cavities and, in particular, whether there is a significant role for NOTES above the diaphragm using the esophagus as a direct carrier to access the mediastinum and the pleural cavity. Transesophageal endoscopic mediastinoscopy, lymph node resection, thoracoscopy, and pleural biopsy have been reported feasible and providing excellent visualization of mediastinal and intrathoracic structures in the experimental setting.
A wide range of NOTES procedures of varying complexity have been described in the experimental setting: peritoneoscopy(1,14–16) liver biopsy, lymphadenectomy(17), tubal ligation(18), oophorectomy(7,19), partial hysterectomy, cholecystectomy and cholecystogastrostomy(20,21), gastrojejunostomy(22), coelctomy, distal pancreatectomy(23) splenectomy(24), pleural biopsy, esophageal myotomy, pericardial window, sentinel node detection performed through the different natural orifices. Cholecystectomy has been extensively evaluated and it has been performed through all possible natural orifices. Ex vivo, in vivo, survival and non-survival studies have demonstrated good initial results in the animal model.
It is difficult today to speculate about the clinical outcome of most of these studies.
They served as a basis for the clinical implemention by providing training and pertinent information on the most sensible issues of NOTES, such as access and closure techniques, manipulation of the endoscope in the peritoneal cavity, spatial orientation, techniques of dissection, exposure, retraction and tissue approximation.
The major highlight of this experimental work is the inadequacy of the flexible endoscope as a platform for performing NOTES procedures. Mixed technologies using transabdominal technologies were evaluated to facilitate the NOTES procedures and the translation to human. These techniques are called “hybrid” in opposition to “pure” NOTES procedures in which only flexible tools are used without any transparietal assistance.
Initial excitement for NOTES has been somewhat tempered by the reality that a NOTES procedure without laparoscopic or needleoscopic-assistance has not been performed by most groups. Indeed, a major issue is the lack of stable operative platform and flexible instruments that allow retraction and exposure of the organs, such as appendix or gallbladder.
Initial pure NOTES transgastric procedures were gastric “PEG” rescue for a patient whose PEG tube was dislodged(25) and peritoneoscopy performed at the time of operative staging of pancreatic tumors(26) or gastric by-pass(27). Rao et al reported transgastric appendectomy, tubal ligation and liver biopsy(28).
Hybrid transgastric cholecystectomy was first performed by Swanstrom in USA and a comparable technique was presented by Auyang et al. (29). The authors utilized a new endoscopic platform, the Transport™ (USGI, USA) that admits large flexible instruments and a suturing device, the G-Prox (USGI, USA), to close the gastrotomy. An initial series of cholecystectomies performed with current endoscopic instrumentation was reported by Dallemagne et al. (30). Peritoneal access is gained using a needle-knife cautery and balloon dilation under laparoscopic visualization Figure 1. Tansparietal assistance for exposure and application of laparoscopic clips is provided by one or two laparoscopic trocars. Dissection of the critical view of safety is performed endoscopically Figure 2. The cystic duct and artery are clipped laparoscopically. The gastrotomy is closed laparoscopically. The gallbladder is extracted out the mouth. All the authors concluded that in order to perform a pure NOTES transgastric cholecystectomy, a safe blind access method, improved retraction, endoscopic hemostatic clips, and reliable closure methods need to be developed.
Currently, transvaginal access is the preferred approach in humans because this route obviates the risk of intestinal content leakage via an imperfectly closed access site. Almost all reported procedures performed through natural orifices use some form of transparietal assistance. Anecdoctical hybrid NOTES appendectomies and cholecystectomies series have been reported by several surgical groups with good outcomes. Transparietal assistance for exposure of the gallbladder, application of laparoscopic clips to seal the cystic duct and assistance in visualization and dissection, is provided by needleport, laparoscopic trocars or transvaginal long grasping forceps(31–42) Figure 3. The time required to complete the procedure showed great variation (range, 35–210 min). The postoperative outcome is favourable in most of studies. Biliary leaks were reported in two studies, treated succesfully by endoscopic drainage and stenting(38,43). Few gynecological complications were reported. Clipping of the elements of the cystic pedicle is still an issue as there is no approved flexible endoscopic clip applier. However, to perform pure NOTES, some surgeons used endoclips or endoloops, or special long clip applier introduced trhough the vagina. No clinical randomized trial comparing NOTES and laparoscopic cholecystectomy has ever been published.
NOTES transgastric appendectomy was intially reported by Rao et al. (28) and was at the origin of the enthousiasm for this new surgical technique. Four other centers reported appendectomy performed through the vagina(35,44–46) or through the stomach(35). These are anecdodictal reports and no conclusion can be drawn. NOTES is apllied in its pure(28,44) or hybrid form (45–47). Transgastric drainage of a perigastric abcess and extraction of an infected gastric band was reported and demonstrated the promising convergence of intra and transluminal therapeutic endoscopy(48).
Reports of NOTES sleeve gastrectomy(49,50), splenectomy(51) and sigmoidectomy(52) must be considered as laparoscopic procedures assisted by transluminal endoscopy. Vision is provided by the flexible endoscope while the majority of the operative steps are performed with laparoscopic trocars and instruments.
- Top of page
- Current status of NOTES
- Technological development
- The Future of NOTES
The current flexible endoscope and flexible instrumentation poses several problems when used outside the confined environment of the lumen of organs. Endoscopes are too floppy, offering small instrument channels, small suction channel, insufflation noncontinuous and not pressure regulated.
Flexibility is necessary to introduce the endoscope through the natural orifices and navigate in the lumen of the organs. Flexibility becomes a problem when the endoscope is pushed outside the lumen of the organs into the peritoneal cavity. Orientation and stability are the preliminary requirements that will enable achievement of surgical procedures. When the target tissue is reached, retraction and dissection are virtually impossible because there is no current instrumentation that provides efficient grabbing and dissection capabilities and the instruments cannot offer triangulation at the tip of the endoscope. The efficacy of maintaining and monitoring pneumoperitoneum is a significant issue. On-demand insufflation with a standard endoscopic insufflator resulted in a marked increase and wide variation in intra-abdominal pressure throughout transgastric peritoneoscopy in an animal model(53).
Therefore, in addition to safe access and closure, it is necessary to develop a new platform for navigation and instrumentation. The general path is to transform an endoscopic concept, where the surgeon is driving simultaneously the optical system and the instruments, into a system where there the surgeon drive independently the instruments while another person guides the optical system. Larger, stronger, eventually articulated, instruments passed through large working channels are necessary. The concept has also to take into consideration the maximum size of the endoscope that will be accepted by the hollow viscus chosen to get access to the peritoneal cavity. The upper limit was fixed, without consultation between research and development teams, at 20 mm for a transgastric access. There are currently various operative platforms and instruments under investigation. The Endosurgical Operating System (EOS, USGI Medical, San Clemente, CA, USA) provides support to large instruments, without possibility of triangulation(54) The direct drive endoscopic system (DDES, Boston Scientific, Natick, MA, USA) is an ergonomic, table-mounted, operative platform providing 5 degrees of freedom to the tip of the instruments(55). Another prototype of operating endoscope is known as the “Anubiscope” (Karl Storz Endoskope, Tuttlingen, Germany) Figure 4 This unique four-way articulating flexible endoscope, with a built-in light and video source, has a 16 mm diameter insertion shaft with an 18mm diameter distal articulating vertebrae section and distal head. The distal head incorporates two opposing, movable arms with 4.2 mm working channels. External to these arms are jaws that function similar to a blunt tip trocar when in the closed position. In the open position, the jaws create triangulation of the working channels. A series of specialized hand instruments offer two-way articulation. The “Endo Samurai” (Olympus Medical, Tokyo, Japan) aims also at providing triangulation of the instruments, using a different operating mode.
A promising solution is the development of robotic endoscopic technology. Single robotisation of the driving wheels on a current endoscope is not helpful(56). An endoscopic robotic platform requires the development of a fully articulated device that can offer forward propulsion to the target tissue, with adequate triangulation of instruments at the tip.
A original robotic system was used with success in transgastric hepatic resections(57). The original feature of this system is the master control that uses movement sensors on the operator’s wrists and fingers and allows triangulation of instruments.
A more futuristic path of development is the use of a cluster of collaborative microrobots introduced in the peritoneal cavity through natural orifices. When they are positioned, the robots provide vision, retraction, and the adequate instrumentation to achieve surgical tasks. Experimentally, such a cluster of microrobots has been successfully used to perform a minimally invasive cholecystectomy.
Although of interest to gastroenterologists and GI surgeons, the future of NOTES lies not only in the development of adequate technologies but also in the patient’s perception of the potential advantages and risks of such an innovative approach. Both parameters are strongly linked, as there is no future for a technique that would be used in a minority of patients.
Cholecystecomy has become the most common NOTES procedure. Although NOTES is still evolving, studies demonstrate that a majority of patients perceive NOTES favorably as a potential technique for a cholecystectomy. This preference for NOTES diminished remarkably if the complication rates were greater than that for a laparoscopic cholecystectomy(60,61). Procedure-related risks, pain, and recovery time were more important than cosmesis, cost, length of hospital stay, and anesthesia type in the choice.
Cholecystectomy provides a model with which to evaluate NOTES. The excellent results of laparoscopic cholecystectomies have created the optimal benchmark. It is difficult to improve on laparoscopic procedures that deserve minimal morbidity despite several small incisions. The ideal application is yet to be found. Common procedures will be targeted for their potential high-volume application which appeals support of the industry. Addition of new diagnostic and therapeutic tools, such as virtual biopsy using confocall microscopy(62), lymph node mapping(63,64), may pave the way to further reduction in invasiveness of surgery.
source: Asian journal of endoscopic surgery