Submucosal tunneling using endoscopic submucosal dissection for peritoneal access and closure in natural orifice transluminal endoscopic surgery: a porcine survival study

• Introduction
• Materials and methods
• Preparation of the pigs
• Transgastric peritoneoscopy using the submucosal tunnel technique
• Follow-up and necropsy
• Outcome measurements
• Results
• Transgastric peritoneoscopy using the submucosal tunnel technique
• Follow-up results
• Discussion
• Acknowledgment
• References

Background and study aims: Safe peritoneal access and gastric closure are the most important concerns in the clinical application of natural orifice transluminal endoscopic surgery (NOTES). We aimed to clarify the feasibility of a submucosal tunnel technique using endoscopic submucosal dissection (ESD) for transgastric peritoneal access and subsequent closure for NOTES.

Methods: Seven female pigs, each weighing about 40 kg were included in the study. The following procedures were performed: (i) after injection of normal saline into the submucosa, the mucosa was cut with a flex knife; (ii) the submucosal layer was dissected using an insulation-tipped electrosurgical knife to make a narrow longitudinal 50-mm submucosal tunnel; (iii) a small incision was made at the end of the tunnel and enlarged with a dilation balloon. After transgastric peritoneoscopy, the mucosal incision site was closed with clips. The following outcome measures were used: (a) evaluation of the technical feasibility of making a submucosal tunnel; (b) clinical monitoring for 7 days; (c) follow-up endoscopy and necropsy; and (d) peritoneal fluid culture.

Results: Natural orifice transluminal endoscopic peritoneoscopy with a submucosal tunnel was successfully carried out in all pigs. The pigs recovered well, without signs of peritonitis. Follow-up endoscopy showed healing of mucosal incision sites without open defects. Necropsy revealed no findings of peritonitis, confirming completeness of gastric closure; there was a thin scar in one pig and adhesion of the omentum in six pigs. Peritoneal fluid culture demonstrated no bacterial growth.

Conclusions: The submucosal tunnel technique is feasible and effective for transgastric peritoneal access and closure.

Introduction

Natural orifice transluminal endoscopic surgery (NOTES) is a new and rapidly evolving concept in the field of gastroenterological surgery that may offer benefits in postoperative patient care by eliminating abdominal wounds altogether [1] [2] [3] [4] [5] [6]. A number of experimental studies have shown the technical feasibility of a variety of NOTES procedures [7] [8] [9] [10] [11], and these have been recently applied in humans [12] [13]. However, safe peritoneal access and secure closure of the access site continue to be the most important concerns with regard to NOTES [4] [5]. The method of endoscopic submucosal dissection (ESD) for early-stage gastric cancer was developed in Japan and allows en bloc resection of large mucosal cancer with a reduced rate of local recurrence [14] [15]. The aim of this study was to determine the feasibility of using ESD to create a submucosal tunnel for transgastric peritoneal access and subsequent gastric closure in a NOTES porcine model.

Materials and methods

The study protocol was approved by the animal care and use committee at the Oita University Faculty of Medicine.

Preparation of the pigs

Seven female domestic pigs weighing 40 – 45 kg were included in the study. The animals were fasted for 48 hours prior to the procedure. All procedures were performed with the pigs under 1 – 2 % sevoflurane general anesthesia with endotracheal intubation. Antibiotics (cefazoline 1g) were intravenously administered to all pigs at the start and end of the procedure. The surgical field, including the oral cavity, was prepared with 10 % povidone iodine solution, and covered with sterile drapes. The endoscope and all accessories were subjected to high level disinfection and gas sterilization.

Transgastric peritoneoscopy using the submucosal tunnel technique

A standard gastroscope (GIF-XQ200; Olympus Medical Systems, Tokyo, Japan), with a transparent hood (D-201-10-704; Olympus), was advanced into the stomach, and the gastric lumen was lavaged with 200 – 300 ml of normal saline solution. First, the gastric wall incision site was selected using the bulge from the pressure of the operator’s finger on the abdominal wall as a marker to prevent injury to adjacent organs. The submucosal tunnel was created as follows, using the ESD technique ([Fig. 1]).

A 23-gauge injection needle was used to inject 5 ml of normal saline solution into the submucosal layer. An initial small incision through the mucosa was then made over this submucosal cushion, with a flex knife (KD-630L; Olympus). The initial incision allowed insertion of an insulation-tipped electrosurgical knife (KD-610L; Olympus) and the incision was extended to 2 cm in length ([Fig. 2] a). Submucosal dissection was performed using an insulation-tipped knife to create a submucosal tunnel of approximately 5 cm in length ([Fig. 2] b, c).

A small incision of the seromuscular layer at the distal end of the submucosal tunnel was made using a flex knife, and a 15-mm dilation balloon (CRE5842; Boston Scientific, Natick, Massachusetts, USA) was inserted into the peritoneal cavity to enlarge the opening.

The gastroscope was then advanced into the peritoneal cavity. Soon after the recognition of abdominal distension, a 14-gauge needle was inserted into the abdominal cavity for decompression of pneumoperitoneum. Intraperitoneal exploration was done for 20 – 30 minutes by advancement, withdrawal, turning, and retroflexion of the endoscope. After this transgastric endoscopic peritoneoscopy, the mucosal incision site was closed using endoclips ([Fig. 2] d).

Follow-up and necropsy

The pigs were fed a liquid diet immediately after recovery from general anesthesia; regular diet was resumed on postoperative day 2.

The physical activity and eating habits of the animals were carefully monitored every day for signs of peritonitis. Follow-up endoscopic examination and necropsy were performed 7 days after the procedure in the first 6 pigs. In the seventh pig, necropsy was done on day 14 to assess the healing process of the submucosal tunnel.

Outcome measurements

The peritoneal cavity was examined for signs of organ injury and evidence of peritonitis. The gastric wall incision site and adjacent structures were carefully inspected, including endoscopic examination of the mucosal incision site. Sections of the submucosal tunnel site were taken for histopathologic examination. The peritoneal cavity around the serosal incision site was irrigated with 100 ml of normal saline solution and the fluid was submitted for microbiologic cultures.

Results

Transgastric peritoneoscopy using the submucosal tunnel technique

In all seven pigs, transgastric peritoneal access and peritoneoscopy were accomplished without complication ([Table 1]). The gastric wall incision site was located in the anterior wall in three pigs and in the posterior wall in four. The mean length of the submucosal tunnel was 54 mm (range 50 – 60), and the mean time required to make a submucosal tunnel by ESD was 16 min (range 6 – 25). After transgastric endoscopic peritoneoscopy had been accomplished, there was no rupture of the submucosal tunnel in spite of the vigorous movement of the endoscope, and closure of the mucosal incision with endoclips was successful in all pigs. The mean time required to close the mucosal incision site was 17 minutes (range 5 – 50) and 4 – 6 clips were used. In the first two pigs closure required 20 minutes or more. However, with this experience having been gained, in the following five pigs the mean closure time was 10 minutes. Gastric distension was maintained without obvious pneumoperitoneum during the endoscopic closure of the mucosal incision site.

Follow-up results

All pigs recovered fully following transgastric endoscopic peritoneoscopy and resumed normal activity on the day of the procedure. They tolerated a liquid diet within a few hours of recovering from anesthesia and ate a regular diet on day 2. All pigs ate well during the survival period. During the postoperative period, there were no clinical signs of peritonitis.

Follow-up endoscopy at 7 days in the first six pigs demonstrated that the mucosal incision sites had healed with small mucosal defects. At necropsy, there was no evidence of organ injury or peritonitis, such as ascites or abscess formation. No fibrous material or tissue adhesion was identified in the peritoneal cavity. Serosal examination of the incision site revealed a thin scar in one pig ([Fig. 3] a) and adhesion of the omentum in five ([Fig. 3] b).

Histopathologic examination of the site of the submucosal tunnel in the first 6 pigs, euthanized on day 7 after transgastric peritoneoscopy, demonstrated healing of the wound with focal transmural fibrosis ([Fig. 4]). There was also a small submucosal abscess with a background of acute inflammation in the fibrous tissue ([Fig. 4]). In the seventh pig, which was euthanized on postoperative day 14, the histologic findings showed excellent healing of the submucosal tunnel with re-epithelialization of the mucosal incision site and fibrous and granulation tissue along the submucosal tract ([Fig. 5]).

None of the peritoneal fluid cultures showed evidence of bacterial growth.

Discussion

Our experimental study in a porcine model demonstrated that natural orifice transgastric endoscopic peritoneoscopy with a submucosal tunnel can be performed successfully without any complications. The submucosal tunnel technique provided safe peritoneal access, secure gastric closure, and aided the excellent healing of the gastric incision site seen by 7 days post-procedure. The ESD technique was useful for making the narrow longitudinal submucosal tunnel.

Safe peritoneal access and secure closure are the most important concerns in NOTES [4] [5]. In previous studies, the usual technique for transgastric peritoneal access has involved a small incision of the gastric wall with a needle-knife, dilation of the small opening using an endoscopic dilation balloon or a sphincterotome, and advancement of the endoscope through the gastric wall into the peritoneal cavity [4] [5] [7]. This technique carries the risk of inadvertent injury to the adjacent intraperitoneal structures. In the present study, the muscular layer could clearly be seen through the use of the submucosal tunnel technique. The seromuscular layer was cut by gently pressing a flex knife fixed at a length of 1 – 2 mm, thus allowing the risk of inadvertent injury to be minimized.

A variety of methods for closure of the gastric incision site have been reported, including the use of endoscopic clips, tissue anchors (T-fasteners) [16], and prototype endoscopic suturing devices [17] [18]. Although several studies have demonstrated successful closure of small transmural gastric wall incisions with endoclips, full-thickness closure is technically difficult because the bite of the clips is superficial [19]. Tissue anchors are simple and useful devices for the closure of transmural gastric wall incisions [16] [20]. However, there is a potential for damage to adjacent organs because the deployment of tissue anchors requires blind transmural puncture of the gastric wall with a hollow needle. In our experimental study, mucosal closure of the entry site with endoclips was sufficient to prevent peritoneal leakage.

There are only a few previous studies on the submucosal tunnel technique for NOTES [20] [21] [22] [23] [24]. Sumiyama et al. developed the “submucosal endoscopy with mucosal flap” (SEMF) safety valve technique, creating a submucosal working space with high-pressure carbon dioxide injection [20] [21]. Their experimental study showed the safety of the SEMF technique in accessing the peritoneal cavity. However, rapid injection of CO₂ created a large submucosal working space, and ulceration due to partial necrosis of the overlying free mucosa occurred in three of four pigs. Our method using ESD allowed creation of an adequate longitudinal narrow submucosal tunnel. Moyer, Pauli, and colleagues also reported on the technical feasibility of the submucosal tunnel in an ex vivo and a live porcine model, where they created a long narrow submucosal tunnel using a combination of sharp and blunt dissection with a grasping forceps [22] [24]. Delius et al. evaluated the effectiveness of various methods of transgastric access with regard to leak pressures, in an ex vivo model. An extended submucosal tunnel of 5 cm showed the best leak resistance compared with standard transgastric access methods such as linear incision and balloon dilation [23]. The present study has demonstrated, in a porcine survival model, the feasibility and effectiveness of the submucosal tunnel technique using ESD.

The submucosal tunnel technique, applied using commercially available equipment, appears to have several advantages. First, the offset seromuscular exit site is distant from the mucosal entry site and the long and narrow submucosal tract can minimize intraperitoneal leakage of gastric content during the NOTES procedure [20] [21]: no bacterial growth was exhibited in the peritoneal fluid cultures from all of the animals in our study. Second, after the endoscope has been withdrawn into the stomach, gastric distension can be maintained without obvious pneumoperitoneum; this provides a better endoscopic view and working space, thereby allowing the easy placement of clips. Finally, the two approximated surfaces of the narrow longitudinal tunnel bond and heal rapidly [20] [22].

In conclusion, our study has shown that the submucosal tunnel technique using ESD is useful for transgastric peritoneal access and subsequent closure, as creation of a narrow longitudinal tunnel is followed by rapid tissue approximation and healing of the gastric wall incision site.

Acknowledgment

We thank Ms. E. Ichimaru for her technical assistance.

Competing interests: None

References

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F. YoshizumiMD 

Department of Gastroenterological Surgery
Oita University Faculty of Medicine

11 Idaigaoka, Yufu, Oita 879-5593, Japan

Fax: +81-97-5496039

Email: Fumitaka@med.oita-u.ac.jp

References

• 1 Baron T H. Natural orifice transluminal endoscopic surgery.  Br J Surg. 2007;  94 1-2
  PubMedSearch in Google Scholar
• 2 Pearl J P, Ponsky J L. Natural orifice translumenal endoscopic surgery: a critical review.  J Gastrointest Surg. 2008;  12 1293-1300
  CrossrefPubMedSearch in Google Scholar
• 3 Swain C P. A justification for NOTES – natural orifice translumenal endoscopic surgery [editorial].  Gastrointest Endosc. 2007;  65 514
  CrossrefPubMedSearch in Google Scholar
• 4 Hawes R H. ASGE/SAGES Working Group on natural orifice translumenal endoscopic surgery.  Gastrointest Endosc. 2006;  63 199-203
  CrossrefPubMedSearch in Google Scholar
• 5 Rattner D, Kalloo A N. ASGE/SAGES Working Group on natural orifice translumenal endoscopic surgery.  Surg Endosc. 2006;  20 329-333
  CrossrefPubMedSearch in Google Scholar
• 6 Voermans R P, Van Berge Henegouwen M I, Fockens P. Natural orifice transluminal endoscopic surgery (NOTES).  Endoscopy. 2007;  39 1013-1017
  Thieme ConnectPubMedSearch in Google Scholar
• 7 Kalloo A N, Singh V K, Jagannath S B. et al . Flexible transgastric peritoneoscopy: a novel approach to diagnostic and therapeutic intervention in the peritoneal cavity.  Gastrointest Endosc. 2004;  60 114-117
  CrossrefPubMedSearch in Google Scholar
• 8 Park P O, Bergstrome M, Ikeda K. et al . Experimental studies of transgastric gallbladder surgery: cholecystectomy and cholecystogastric anastomosis.  Gastrointest Endosc. 2005;  61 601-606
  CrossrefPubMedSearch in Google Scholar
• 9 Jagannath S B, Kantsevoy S V, Vaughn C A. et al . Peroral transgastric endoscopic ligation of fallopian tubes with long term survival in a porcine model.  Gastrointest Endosc. 2005;  61 449-453
  CrossrefPubMedSearch in Google Scholar
• 10 Feretis C, Kalantzopoulos D, Koulouris P. et al . Endoscopic transgastric procedures in anesthetized pigs: technical challenges, complications, and survival.  Endoscopy. 2007;  39 394-400
  Thieme ConnectPubMedSearch in Google Scholar
• 11 Kantsevoy S V, Jagannath S B, Niiyama H. et al . Endoscopic gastrojejunostomy with survival in a porcine model.  Gastrointest Endosc. 2005;  62 287-292
  CrossrefPubMedSearch in Google Scholar
• 12 Marescaux J, Dallemagne B, Perretta S. et al . Surgery without scars.  Arch Surg. 2007;  142 823-826
  CrossrefPubMedSearch in Google Scholar
• 13 Bessler M, Stevens P D, Milone L. et al . Transvaginal laparoscopically assisted endoscopic cholecystectomy: a hybrid approach to natural orifice surgery.  Gastrointest Endosc. 2007;  66 1243-1245
  CrossrefPubMedSearch in Google Scholar
• 14 Ono H, Kondo H, Gotoda T. et al . Endoscopic mucosal resection for treatment of early gastric cancer.  Gut. 2001;  48 225-229
  CrossrefPubMedSearch in Google Scholar
• 15 Gotoda T, Yamamoto H, Soetikno R M. Endoscopic submucosal dissection of early gastric cancer.  J Gastroenterol. 2006;  41 929-942
  CrossrefPubMedSearch in Google Scholar
• 16 Ikeda K, Fritscher-Ravens A, Mosse C A. et al . Endoscopic full-thickness resection with sutured closure in a porcine model.  Gastrointest Endosc. 2005;  62 122-129
  CrossrefPubMedSearch in Google Scholar
• 17 Meireles O R, Kantsevoy S V, Assumpcao L R. et al . Reliable gastric closure after natural orifice translumenal endoscopic surgery (NOTES) using a novel automated flexible stapling device.  Surg Endosc. 2008;  22 1609-1613
  CrossrefPubMedSearch in Google Scholar
• 18 Hu B, Chung S C, Sun L C. et al . Eagle Claw II: A novel endosuture device that uses a curved needle for major arterial bleeding: a bench study.  Gastrointest Endosc. 2005;  62 266-270
  CrossrefPubMedSearch in Google Scholar
• 19 Merrifield B F, Wagh M S, Thompson C C. Peroral transgastric organ resection: a feasibility study in pigs.  Gastrointest Endosc. 2006;  63 693-697
  CrossrefPubMedSearch in Google Scholar
• 20 Sumiyama K, Gostout C J, Rajan E. et al . Submucosal endoscopy with mucosal flap safety valve.  Gastrointest Endosc. 2007;  65 688-694
  CrossrefPubMedSearch in Google Scholar
• 21 Sumiyama K, Gostout C J, Rajan E. et al . Transgastric cholecystectomy: transgastric accessibility to the gallbladder improved with the SEMF method and a novel multibending therapeutic endoscope.  Gastrointest Endosc. 2007;  65 1028-1034
  CrossrefPubMedSearch in Google Scholar
• 22 Moyer M T, Pauli E M, Haluck R S. et al . A self-approximating transluminal access technique for potential use in NOTES: an ex vivo porcine model.  Gastrointest Endosc. 2007;  66 974-978
  CrossrefPubMedSearch in Google Scholar
• 23 Delius S V, Gillen S, Doundoulakis E. et al . Comparison of transgastric access techniques for natural orifice transluminal endoscopic surgery.  Gastrointest Endosc. 2008;  68 940-947
  CrossrefPubMedSearch in Google Scholar
• 24 Pauli E M, Moyer M T, Haluck R S. et al . Self-approximating transluminal access technique for natural orifice transluminal endoscopic surgery: a porcine survival study.  Gastrointest Endosc. 2008;  67 690-697
  CrossrefPubMedSearch in Google Scholar

F. YoshizumiMD 

Department of Gastroenterological Surgery
Oita University Faculty of Medicine

11 Idaigaoka, Yufu, Oita 879-5593, Japan

Fax: +81-97-5496039

Email: Fumitaka@med.oita-u.ac.jp