In the past few years, natural orifice translumenal endoscopic surgery (NOTES) made the transition from the laboratory to human clinical trials. Approximately 30 studies are under way, some of which have been completed with results due next year. According to Juliane Bingener-Casey, M.D., and Christopher J. Gostout, M.D., both of Mayo Clinic in Minnesota, these trials are already providing a clearer picture of the advantages, limitations and possible future role of NOTES in clinical practice.
One notable example is a prospective multicenter trial undertaken by the Natural Orifice Surgery Consortium for Assessment and Research (NOSCAR) comparing laparoscopic cholecystectomy with transvaginal and transgastric NOTES cholecystectomy.
The NOSCAR trial is of particular interest because thousands of NOTES cholecystectomies have been performed worldwide, most using transvaginal access points. Anecdotally, NOTES leads to less postoperative pain and may even eliminate the need for analgesics. But Dr. Bingener-Casey says surveys from other countries — and her own experience — reveal that a surprising number of women are uncomfortable with the transvaginal approach.
"We were having a hard time enrolling patients for a feasibility trial using transvaginal NOTES for gallbladder removal," she says. "So we surveyed women, asking if they preferred a transvaginal or transabdominal procedure. Many said transvaginal access was fine for gynecological procedures but not for appendectomy or cholecystectomy."
Patient acceptance is only one of the clinical challenges NOTES faces. Physician skill level and background training are another.
Dr. Gostout explains, "Surgeons find it difficult to use a flexible platform, which is very natural for gastroenterologists. But gastroenterologists have a hard time finding their way in the peritoneal cavity. If gastroenterologists are going to perform NOTES operations, they will need to know surgical landmark anatomy. Dr. Bingener-Casey and I live and work in both areas, so we've been able to collaborate successfully. In our developmental endoscopy unit we're working on specific targeted NOTES applications that we think would be ideal for both gastroenterologists and surgeons to perform."
One such application is cancer staging, once routinely performed laparoscopically by gastroenterologists.
"I am convinced there can be a significant rebirth of staging peritoneoscopy using NOTES-style approaches," Dr. Gostout says. "Researchers in Ohio are exploring the use of transgastric endoscopic peritoneoscopy for the diagnosis of metastases in pancreatic cancer. It's an easy technique that I believe will eventually catch on because intuitively it makes sense."
Most NOTES procedures are hybrids that combine elements of laparoscopy and flexible endoscopy. A lack of next-generation instruments and platforms, the advanced skills required to perform many NOTES procedures, and the rising popularity of single-port laparoscopy have limited the adoption of pure NOTES operations. But according to Dr. Gostout, NOTES "opened the door to be much more aggressive in performing minimally invasive surgery inside the gut lumen."
Reflecting this increased comfort level, Mayo researchers have proposed esophageal myotomy using submucosal endoscopy with mucosal flap (SEMF) as a new treatment for achalasia. The technique creates a working space or tunnel between the inner lining of the gut and the muscular layer, allowing insertion of the endoscope and access to the muscle of the lower esophageal sphincter. The procedure, shown to be feasible in pig models, is currently being performed clinically.
Another NOTES-like procedure is endoscopic resection of benign gastroesophageal junction tumors. Lodged in the difficult space between the esophagus and stomach, the tumors are challenging to treat using standard surgical techniques. At Mayo Clinic, surgeons used dual endoscopies to remove tumors in one piece from the deep layers of the gut wall, with "startlingly good" results, Dr. Gostout says.
Mayo doctors have also successfully performed translumenal endoscopic repair for perforated ulcer disease, a condition with notoriously high mortality and morbidity rates.
Dr. Bingener-Casey explains, "We used the omentum to close the stomach hole, similar to the open operative approach, and we found that the translumenal approach worked at least as well as laparoscopy."
The transgastric route also has been used for incision and drainage of pancreatic necrosis in the septic fluid stage. "Essentially, we poke a hole in the back wall of the stomach and pass the endoscope into the lesser sac," Dr. Gostout says. "It's a safe, predictable route to clean out fluid and debris, and it avoids the large open abdomen of surgical necrosectomy. It's like going from a land line to wireless." He adds that continued treatment of pancreatic necrosis includes repeat endoscopy, nasojejunal feeding, nasotransgastric drainage and lavage, and percutaneous drainage and irrigation.
Other NOTES spinoffs used at Mayo include revisions of gastric bypass anastomoses using a suturing device initially developed for NOTES and vertical gastrectomy. "Neither is strictly a NOTES procedure," Dr. Gostout says, "but they are highly sophisticated interventions that rival anything we've ever dreamed of."
Both doctors acknowledge that replacing successful existing procedures with NOTES applications isn't the point.
"What drives us is what will benefit the patient most, rather than pure NOTES procedures," Dr. Gostout says. "But I do think the intralumenal spinoffs will continue to evolve. There will be new ones because of our greater comfort level working inside the gut lumen. And if we accidentally go outside the lumen, then we know what to do."