Natural orifice translumenal endoscopic surgery (NOTES) embodies the traits of promising and disruptive technology with growing interest around the globe [1]. The NOTES procedure has the potential to eliminate abdominal wall incisions and to decrease postoperative pain. The peritoneal access-site closure continues to be one of the main challenges facing NOTES [2].

This study aimed to evaluate the use of an automated flexible stapling device (SurgASSIST; Power Medical Interventions, Langhorne, PA, USA) for closure of the gastrotomy incision in a porcine model.

Methods

This study was approved by the Johns Hopkins University School of Medicine Animal Care Institutional Review Board. We performed four acute experiments using 50-kg pigs (Sus scrofus domesticus). All procedures were performed with the animals under 1.5% to 2% isoflurane general anesthesia using 7-mm endotracheal intubation (Mallinckrodt Co, C. D. Juarez, Chih, Mexico). The preanesthesia medications were composed of an intramuscular injection of Telazol 100 mg/ml (tiletamine HCl C zolazepam HCl; Lederle Parenterals, Inc, Carolina, Puerto Rico) reconstituted with 100 mg/ml of ketamine HCl and 100 mg/ml of xylazine at a total dose approximating 0.05 ml/kg. The marginal ear vein was injected with 1 g of thiopental sodium at a dose of 6.6 to 8.8 mg/kg.

The procedure started with insertion of a 12-cm-long 14-gauge Veress needle infraumbilically through the abdominal wall. This was followed by insufflation of carbon dioxide (CO2) using a standard autoregulated laparoscopic insufflator equipped with a built-in manometer (Electronic Endoflator 264305 20; Karl Storz, Tuttlingen, Germany) to accomplish pneumoperitoneum and ensure stable and well-controlled intraabdominal pressures, with a 12 mmHg setting point pressure and a 10 l/min of CO2 flow rate [3].

A 60-cm-long automated flexible stapler was introduced per-orally and advanced into the stomach to determine the future gastrotomy site (between the stapler’s arms). Once that area was visually identified and the distance from the front teeth recorded, the device was removed from the stomach.

A forward-viewing double-channel upper endoscope (GIF- 2T160; Olympus Optical Co. Ltd., Tokyo, Japan) was advanced into the stomach. The gastric wall was punctured with a triple-lumen needleknife (Wilson-Cook Medical Inc., Winston-Salem, NC, USA) using pure cautery at 20 J followed by pure cut at 30 J (Valleylab SSE2L; Tyco Healthcare Group LP, Boulder, CO, USA). The CRE dilating balloon (Boston Scientific Microvasive, Natick, MA, USA) was inserted into the gastric wall puncture site, then distended to 20 mm to gain access to the peritoneal cavity. The endoscope was advanced into the peritoneal cavity.

After peritoneoscopy, the endoscope was withdrawn into the stomach, and the stapler loaded with “Blue Load” staples (with a leg length of 3.3 mm and a median closed staple height of 1.2 mm) was reintroduced into the stomach. The arms of the stapler were opened. Two forceps were advanced through the working channels of the endoscope to grasp both edges of the gastric wall incision and to position them between the opened stapler arms. The arms of the stapler were closed, encompassing the gastrotomy site. Using the automated firing system, the stapler was fired, performing complete closure of the gastrotomy site.

In the first experiments, a load with the cutting blade was used, which made a transection between the lines of staples. Alternatively, in the subsequent experiments (pigs 2–4), a stapler’s loads without the cutting blade were used.

After closure of the gastric wall incision, the stomach was fully distended, then filled with iohexol contrast (350 mgI/ml Ominipaque; GE Healthcare Inc, Princeton, NJ, USA) under fluoroscopic observation to assess the water tightness of the gastric incision closure. Then the animals were killed, and postmortem examination was performed to study adequacy of the closure and to check the intraperitoneal organs for possible transgastric access and closure-related complications.

Results

Four acute animal experiments were performed. In all the experiments, transgastric access to the peritoneal cavity and peritoneoscopy were accomplished without complications.

The delivery and positioning of the stapler required 14.5 ± 4.7 min and were achieved with technical difficulties mostly due to a short working length (60 cm) of the device. The distance between the incisors and gastroesophageal junction in 50-kg pigs was approximately 55 cm. With the current working length of the flexible stapler, we had to make the gastric wall incision in the cardiac region of the stomach within 5 cm from the gastroesophageal junction.

The use of the double-channel endoscope facilitated positioning of both edges of the gastric wall incision (with two endoscopic grasping forceps) between the opened arms of the stapler. Automated control allowed proper alignment of the stapler arms, their adequate approximation, and prevention of misfiring. The firing sequence of the staple lasted only 15 s and created four linear rows of staples, completely closing the gastric wall incision and creating 60-mm-long staple line.

The postmortem examination of pig 1 (when a cutting blade was used) demonstrated a full-thickness closure of the gastric wall incision. However, the cutting blade caused a transmural linear cut right at the end of the line of staples. For this reason, we stopped using the stapler loads with a cutting blade. In the three remaining animals (pigs 2–4), we were able to achieve a full-thickness closure of the gastric wall incision with good serosa-to-serosa approximation and without any complications. The x-ray with iohexol contrast did not show any leaks of the contrast through the line of staples.

Discussion

The concept of NOTES as a less invasive alternative to laparoscopic and open surgery is gaining popularity among gastroenterologists and surgeons [2]. Multiple NOTES procedures in animal models have been reported by researchers in the United States and abroad [4–17]. Nevertheless, many technical aspects of translumenal interventions remain unsolved including optimal access site, prevention of intraperitoneal infection, spatial orientation inside the peritoneal cavity, and development of new instruments [2, 18–21]. Among the unanswered questions, dependable closure of the peritoneal access site continues to be one of the main challenges facing NOTES [22].

Currently available methods that could potentially be used for closure of the transluminal access site include tissue anchors [23, 24], endoscopic clips [25–27], suction-based prototype suturing devices [28, 29], and other instruments [30–32]. Several studies have evaluated the use of different tissue anchors (T-bars) for closure of the transmural gastric wall incisions [23, 24]. Publications of these studies have demonstrated successful closure of small and large transmural defects of the gastric wall with tissue anchors. But deployment of the tissue anchors requires transmural puncture of the gastric wall with a hollow needle, which carries the T-bars [23] Although in published reports, the authors did not describe any complications related to the use of this delivery mechanism, there is a potential of damage to the adjacent organ or introduction of infection into the peritoneal cavity when the tissue anchors are deployed [33]. In addition, none of the published studies was designed to evaluate the use of tissue anchors specifically for closure of gastric wall incisions after NOTES procedures.

Currently, a variety of endoscopic clips are commercially available, easy to use, and gaining in popularity among gastroenterologists and surgeons for various endoluminal interventions [34, 35]. Several reports describe the clinical use of endoclips for mucosal closure of pathologic or iatrogenic gastrointestinal tract perforations [34–39], but dedicated use of endoscopic clips for NOTES access closure has yielded suboptimal results [28]. Thompson et al. [28] compared several methods of gastric closure including endoclips, surgical suturing, and a suction-based suturing device. Their study demonstrated that mucosal closure with endoclips results in significant air and fluid leakage via the line of endoclips.

Surprisingly, the full-thickness closure with a suction-based suturing device was more reliable than surgically made sutures [28]. The obvious weakness of this approach is the need to place the sutures before access to the peritoneal cavity, which may complicate subsequent translumenal intervention. In addition, with suction-based suturing devices, the depth of the sutures (too shallow or too deep) is difficult to control. This problem even has led to unintended capture of the small bowel loop adjacent to the stomach when another suction-based suturing device was used [29].

The current study aimed to evaluate the use of an automated stapler (SurgASSIST) for closure of the gastrotomy incision in a live porcine model. This flexible device has a built-in automated control, which allows proper alignment of the stapler arms, their adequate approximation, and prevention of misfiring. During these experiments we were able to make a full-thickness 60-mm-long line of staples, reliably closing the site of transgastric access into the peritoneal cavity.

In the first animal, we used the stapler load with a cutting blade, which led to a damage of the gastric wall right at the end of the staple line. To correct this problem, we started using stapler loads without a cutting blade and did not have any problems or complications with the three remaining animals. Postmortem examination demonstrated full-thickness closure of the gastric wall incision with good serosa-to-serosa approximation.

In our experiments, the location of the gastrotomy was restricted to the cardiac region within 5 cm from the gastroesophageal junction due to the short working length (60 cm) of the stapler. This limitation will be corrected in the next generation of the stapler (Natural Orifice Linear Cutter; Power Medical Interventions) currently under development. This new device will have a longer working shaft, a smaller diameter, and articulating abilities, which will allow closure of the gastrotomy made in any portion of the stomach.

In conclusion, the flexible stapling device may provide a simple and reliable technique for lumenal closure after NOTES procedures. Further survival studies currently are under way to evaluate the long-term efficacy of gastric closure with the stapler after intraperitoneal interventions.

Fig. 1
figure 1

Both edges of the gastric wall incision are grasped with endoscopic forceps

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Fig. 2
figure 2

The arms of the stapler are closed around the gastric wall incision, and the stapler is ready to fire (retroflex view)

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Fig. 3
figure 3

Closure of the gastric wall incision with a linear line of staples is completed

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