Meadows and Chamberlain
inferior to hand-sewn closure in regards to burst pressure. Since no endoscopic instrumentation was used to close the defects in this study, this data does not necessarily reflect the quality of the seal and burst pressures that may be achiev- able during in vivo NOTES procedures. In vivo studies and additional ex vivo analysis are vital to more fully understand the advantages and disadvantages of each device.
A major concern facing transgastric NOTES develop- ment and transrectal approaches centers on the issue of peritoneal contamination and the potential development of intra-abdominal infection. Lomanto et al compared the risk of peritoneal contamination after a transvaginal versus a transgastric NOTES approach.12 These authors adminis- tered preoperative intravenous antibiotics (cephazolin, 1 g) followed by povidone-iodine/saline lavage to either the stom- ach or vagina in a porcine animal model. A transgastric left tubal ligation or a transvaginal cholecystectomy was then performed. Peritoneal cultures were obtained immediately after entry into the abdomen, at the end of the procedure, and at euthanasia. Three of six (50%) animals in the transgastric group developed signs of postoperative peritonitis with evidence of peritoneal abscesses and isolation of E. coli at autopsy; whereas no infections were noted in the transvaginal cholecystectomy group.
In a study designed to assess the need for decontamination of the stomach prior to gastrotomy, Narula et al performed diagnostic transgastric peritoneoscopy on 10 patients.17 Thirty minutes prior to the procedure, patients received a preoperative dose of prophylactic antibiotics (cephazolin, 1 g). A gastric lavage with povidone-iodine/saline solution was not per- formed. Intragastric and peritoneal samplings were obtained before and after creation of the gastrotomy including qualita- tive and quantitative microbiological cultures. No infectious complications were reported in any patient. The authors con- cluded that although transgastric instrumentation may result in contamination of the abdominal cavity (642.1 CFU/mL post-gastrotomy versus 132.1 CFU/mL pre-gastrotomy), quan- titatively the number of pathogens was below the threshold necessary to result in a clinically significant infection and no cross-contamination between the intragastric bacterial species and peritoneal species was noted.
It should be noted that transvesical NOTES approach to the peritoneal cavity has had an initial enthusiastic phase.18 In 2007, Rolanda et al performed an exclusively “pure” natural orifice cholecystectomy on 7 porcine models through a combined transgastric and transvesical approach.19 The transvesical port allowed for visualization of the gastrotomy and the utilization of rigid instrumentation for retraction of
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the gallbladder. The dissection, clipping and sectioning of the cystic duct and artery and removal of the gallbladder were done entirely through the gastrotomy port. Although 5 of the 7 (71.4%) porcine cholecystectomies were com- pleted without complication, no further investigations of this approach for cholecystectomies have been published. Cindolo and his urologist team summarized that transvesical NOTES seem likely to flourish only in specific urological conditions, if at all.18
Technological limitations: exposure, flexibility, and retroflexion
Flexible endoscopy is the only platform currently available to obtain peroral transgastric access to the peritoneum.20 In general, flexible endoscopes are designed for diagnostic and therapeutic procedures inside the gastrointestinal tract lumen rather than the open space of the peritoneal cavity. Spatial orientation, retroflexion instability of the instrument, and small instrument channels pose major challenges yet to be overcome.21–24 Specifically, visualization of the gallbladder in the right upper quadrant requires the scope to be retroflexed, which significantly limits the rigidity of instruments that can be used and developed for transgastric surgery.25 This lack of rigidity severely limits the counter forces down the shaft which can be applied to adequately retract tissue and apply strong sutures or clips.2,26 Several attempts to develop rigid or semirigid platforms to overcome this limitation are currently being explored. Swanstrom and described a novel shape-locking overtube that stabilizes the endoscope while in a retroflexed position.27 This 18-mm overtube (USGI Medical, San Clemente, CA, USA) has multiple channels which allow a camera and two instruments with up to 5.5-mm diameter to be used. Additional smaller channels are also present to per- mit insufflation and irrigation.As expected, results with these early devices were not ideal, and only one of three (33.3%) attempted porcine model NOTES cholecystectomies were completed successfully.26 Sumiyama and Gostout described a submucosal endoscopy with mucosal flap (SEMF) tech- nique for peritoneal access.28 This is carried out by creating a submucosal bleb formed by the injection of CO2 into this layer. A needle knife incision is made at the margin of this bleb. On the opposite side of this incision and within the submucosal space, an endoscope with an attached endoscopic mucosal resection cap is inserted to resect the muscular layer to gain access to the peritoneal cavity. This flap-creating technique has advantages of safer access by avoiding injury to surrounding structures, and allows for easy maintenance of gastric distension throughout the procedure. By creating
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