Natural Orifice Transluminal Endoscopic Surgery (NOTES): A Review

Michael Parker, MD, Ravi Alapati, MD and Ashutosh Kaul, MD


March 21, 2007

NOTES: Where it Stands

Flexible endoscopy is expanding its role from diagnostics and simple therapeutics to advanced surgical techniques applicable to disease of the gastrointestinal tract and peritoneal structures. In what looks more like science fiction, surgeons have utilized body openings to get access to abdominal cavity. Advancing technologies, especially fibre-optic instrumentation, has aided physicians. Natural orifice transluminal endoscopic surgery (NOTES) is an emerging experimental alternative to conventional surgery that eliminates abdominal incisions and incision-related complications by combining endoscopic and laparoscopic techniques to diagnose and treat abdominal pathology.[1] NOTES thus combines laparoscopic and endoscopic techniques in order to access the peritoneal cavity by means of mouth, anus, or possibly vagina. Current research in the United States has been confined to animal models, but human experience has been gained by Drs. G.V. Rao and Nageshwar Reddy at the Asian Institute of Gastroenterology, Hyderabad, India, where transoral, transgastric appendectomies have been performed.[2]

Potential advantages of NOTES in comparison with laparotomy and laparoscopy include absence of incisional complications including pain, hernias and external wound infections. Hopefully there would be fewer adhesions, a decreased need for anesthesia, and eventually a shorter hospital stay. However, novel advanced technologies and instruments must be developed specifically for NOTES. The endoscopes must have adequate resolution, channel size, and the ability to lock into position inside the peritoneum, as the instruments must parallel the capabilities of laparoscopic instruments.[3]The need for tissue triangulation has to be accomplished from a single instrument and so devices with multiple heads have to be developed.

NOTES procedures performed in animals have included cholecystectomy, appendectomy, salpingectomy, oophorectomy, and adrenalectomy. Kalloo and colleagues reported success with NOTES for the purpose of liver biopsy, gastro-jejunostomy and tubal ligation.[4,5,6] More recently, they published their results from six porcine transgastric endoscopic splenectomies. In these procedures, the peritoneal cavity was entered in a trans-gastric fashion using a 4-mm needle knife followed by enlargement with a 1.5 cm pull-type sphincterotome. Using retroflexion endoscopy, grasping forceps, electrocautery, polypectomy snare, endoloops and clips, the omentum was cauterized and divided, while both sets of splenic vessels were ligated with endoloops.[7]

The application of NOTES in the intensive care setting has been studied by Onders group with regard to diaphragmatic pacing used to facilitate the weaning of ICU patients from mechanical ventilation. In four pigs studied, the diaphragm was mapped using an endoscopic electro-stimulator catheter to locate the motor point--a point where stimulation induces complete contraction of the diaphragm. In one animal, a percutaneous electrode was placed into the motor point under transgastric endoscopic visualization with subsequent diaphragmatic pacing in conjunction with mechanical ventilation.[8]

The transcolonic approach has also been investigated for its potential feasibility in performing NOTES. Pai and colleagues have reported success in performing porcine transcolonic cholecystectomies. By means of an anterior, transcolonic incision made 15-20 cm from the anus, the authors ligated the cystic duct and artery in standard fashion, removed the gallbladder and closed the colonic incision using endoloops and/or endoclips. Despite the incomplete colonic closure of one animal resulting in suspected peritonitis and subsequent euthanasia at 48 hours, the remaining 4 subjects flourished postoperatively and were euthanized at 2 weeks for necropsy.[9]

The same group from Boston reported success in another animal study. They used bowel preparation with tap-water enemas, cefazolin, and povidone-iodine lavage and reported success in visualization of the porcine stomach, liver, gallbladder, spleen, small bowel, colon and peritoneal surfaces in six animals. At 14 days, necropsy showed well-healed and completely closed colonic incision sites, though microscopic inflammatory changes were visualized, including micro-abscesses. Incision-related adhesions were identified in 4 of the 6 animals. In comparison with the trans-gastric approach, a trans-colonic approach may provide more consistent identification of structures in the upper abdomen and provides better en face orientation and scope stability.[10]

One technical challenge regarding NOTES involves the need for adequate closure of the visceral surface being crossed when entering the peritoneum. Seaman's group investigated porcine gastric tissue apposition by evaluating T bar, T bar with mesh bolster, star and basket. Using interval endoscopy for intraluminal assessment and subsequent necropsy and histology following euthanasia, the authors report more promising results with the basket tissue anchors, which demonstrated the tallest plications and contained apposed muscularis propria with evidence of serosal fusion not seen with the other plicators. The basket tissue anchors had a 78% retention rate in comparison with T bar (67%), T bar with mesh (67%) and star anchors (22%). The authors noted no gastric adhesions and no evidence of peri-gastric inflammatory changes.[11]

The future promise relies on the analysis of the deficiencies of current endoscopes and the review of future endoscopes, as well as the development and investigation of current tissue approximation systems. Specifically, Bardaro has evaluated the "R" scope (Olympus, Tokyo, Japan) and the Transport and Cobra scopes (USGI Medical, San Capistrano, CA) as "endoscopes of the future"[12] In addition, Swanstrom has discussed the Eagle Claw (Olympus), the Swain system (Ethicon, Cincinnati, OH), and the G-prox (USGI Medical) as tissue approximation systems being presently investigated in clinical trials.[3] Finally, Oleynikov and Lehman commented on the constraints on visual feedback and dexterity in NOTES and have developed telerobotics and in vivo robotics to address these limitations.[13] They have utilized small mini-robots which are inserted via a small gastrotomy into the peritoneal cavity, controlled wirelessly and have been clinically used to do liver biopsy.

Surgeon involvement is paramount to the success of NOTES. Postgraduate courses organized by groups including the American Society for Gastrointestinal Endoscopy (ASGE), the American College of Surgeons (ACS), and SAGES will allow surgeons and surgeons-in-training to improve their skills and allow collaboration to help develop new technologies and direct future research in luminal access surgery.[14]. SAGES has taken a leadership role in promoting research and training in these developing technologies. The future looks promising though it will be some time before they will be used routinely.


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