Closing the gap: progress for NOTES

“Healing is a matter of time, but it is sometimes also a matter of opportunity.”

Hippocrates, ca. 460 BC – ca. 370 BC

Some practitioners believe that the final boundary for the flexible gastrointestinal endoscope exists beyond the gastrointestinal lumen and into the cavities of the peritoneum and thorax, which is the premise for natural orifice transluminal endoscopic surgery (NOTES) [1]. In order for NOTES to gain widespread clinical use, secure closure of the gastrointestinal incision is critical, as mandated by the Natural Orifice Surgery Consortium for Assessment and Research (NOSCAR) [2].

Two papers in this issue of Endoscopy evaluate the use of an over-the-scope clip (OTSC) system (Ovesco Endoscopy AG, Tübingen, Germany) for NOTES gastrotomy closure. This device is a superelastic nitinol clip that is placed over the tipp of the endoscope. Using the OTSC twin grasping forceps with two independently functioning jaws, tissue is grasped on either side of the incision and withdrawn into the clip. The clip is then deployed in a fashion similar to standard band ligation.

Voermans et al. evaluated the OTSC system in ex vivo pig stomachs that had gastrotomy created by a needle puncture followed by 18-mm balloon dilation [4]. Leak tests were then performed with a previously validated leak test system and the results compared with those for previously performed hand-sutured closures. Closure with the OTSC system was quick (a median time of 3 minutes) and was as durable as hand-suturing (leak pressure 233 mm Hg [SD 47] in the OTSC group versus 206 mm Hg [SD 59] in the hand-suturing group). One incision was not successfully closed because of slippage of the clip on the serosal side and therefore was not subjected to leak testing. This is surprising since an ex vivo study is not subjected to the challenges of an in vivo study, namely having to deal with intestinal motility or challenging anatomic locations. Although well-performed, this study like all ex vivo studies may have conclusions that are not applicable to real-life clinical situations.

What did we learn from this study? First, that when properly placed the OTSC provides secure closure, comparable to that from hand-suturing, for gastrotomies created by balloon dilation. Secondly, even in the most nearly ideal situation, slippage of the clip may occur. There remain several unanswered questions. Is it difficult to remove the clip if it is not correctly placed? Is it challenging to place a second clip? What about gastrotomies that are not created by balloon dilations but rather made by an incision? A balloon-created gastrotomy may be inadequate for organ removal.

The answers to some of but not all these questions were addressed in the study by von Renteln and colleagues who performed a randomized controlled survival study of OTSC versus endoscopic clips in a porcine model [4]. In this study the gastrotomies were created in an identical fashion to those in the study of Voermans et al.. The Ovesco twin grasping forceps were used for both the OTSC and the standard endoscopic clips. Intraoperative leak tests were used to assess the integrity of the closure and additional clips were placed as necessary. As in the study of Voermans et al., OTSC placement was quick (8.5 minutes versus 31.5 minutes for standard clips). None of the pigs with OTSCs had a positive leak test after closure as compared to 40 % of those with standard clips. What was surprising was that only 30 % of the OTSC group had closures that were found at necropsy to incorporate the mucosa, submucosa, and muscularis. None of the OTSC group had peritonitis compared with 30 % of the standard clip group, and 20 % of the OTSC group had perigastric abscess compared with 30 % of the standard clip group. It would be interesting to know if the pigs who had perigastric abscesses were the ones with superficial closures. The von Renteln study confirms the finding of Voermans et al. that OTSC placement is quick and secure. The high infectious complication rate of the OTSC group is concerning and raises questions about the method of antibiotic administration (intramuscular, not intravenous) and the solution used for gastric sterility. Some concerns could have been addressed by having a third arm of the study that used conventional suturing as a means of closure. Could performance of the leak test itself have contributed to leakage and infectious complications? Another unanswered question that remains is whether OTSC is effective for closure of gastrotomies created by an incision. The fact that no leakage occurred in the OTSC group although 30 % of pigs did not have full-thickness wall approximation challenges the notion that full-thickness closure is the Holy Grail for secure closure.

These are exciting times for gastroenterologists and surgeons. The race to find solutions for the challenges of NOTES will have many winners including standard endoscopic practice and ultimately and most importantly, our patients.

Competing interests: A. Kalloo is a consultant for and founding member and equity holder of Apollo Endosurgery.

References

• 1 Giday S A, Kantsevoy S V, Kalloo A N. Current status of natural orifice translumenal surgery.  Gastrointest Endosc Clin N Am. 2007;  17 595-604
• 2 Rattner D, Kalloo A. ASGE/SAGES Working Group on Natural Orifice Translumenal Endoscopic Surgery. October 2005.  Surg Endosc. 2006;  20 329-333. Gastrointest Endosc 2006; 63; 199 – 203. Available at: http://www.noscar.org/documents/NOTES_White_Paper_Feb06.pdf
• 3 Voermans R P, van Berge Henegouwen M I, Bemelman W A, Fockens P. Novel over-the-scope clip system for gastrotomy closure in natural orifice transluminal endoscopic surgery (NOTES): an ex vivo comparison study.  Endoscopy. 2009;  41 1052-1055
• 4 Renteln D von. et al . Randomized controlled trial comparing endoscopic clips and over-the-scope clips for closure of natural orifice transluminal endoscopic surgery gastrotomies.  Endoscopy. 2009;  41 1056-1061