In search of the best peritoneal adhesion model: comparison of different techniques in a rat model.

BACKGROUND: Adhesion-related complications after abdominal surgery result in significant morbidity and costs. Results from animal studies investigating prevention or treatment of adhesions are limited due to lack of consistency in existing animal models. The aim of this study was to compare quality and quantity of adhesions in four different models and to find the best model. MATERIALS AND METHODS: This study was approved by the University of Missouri Animal Care and Use Committee (ACUC). Forty female rats were randomly assigned to four different groups of 10 animals each. Adhesion created was performed utilizing the four techniques: Group 1 - parietal peritoneum excision (PPE), Group 2 - parietal peritoneum abrasion (PPA), Group 3 - peritoneal button creation (PBC), and Group 4 - cecal abrasion (CA). Rats were allowed to recover and necropsy was performed on postoperative d 14. Adhesions were scored by an established quantitative and qualitative scoring systems. The midline incision served as the control in each animal. RESULTS: The four groups were not equal with respect to both quantity score (P<0.001) and quality score (P=0.042). The PBC group had the highest quantity of adhesions. The highest quality of adhesion was seen in the PPE group. A multivariate analysis carried out to quantify the performance of each model clearly demonstrated that PBC exhibited the best results in terms of both quantity and quality. CONCLUSIONS: The button technique (PBC) is most consistent and reproducible technique for an intra-abdominal adhesion model. This model can help in the study and development of substances to prevent adhesion formation in the future.

Transvaginal repair of a large chronic porcine ventral hernia with synthetic mesh using NOTES.

BACKGROUND: Ventral incisional hernias still remain a common surgical problem. We tested the feasibility of transvaginal placement of a large synthetic mesh to repair a porcine hernia. METHODS: Seven pigs were used in this survival model. Each animal had creation of a 5-cm hernia defect and underwent a transvaginal repair of the defect with synthetic mesh. A single colpotomy was made using a 12-cm trocar for an overtube. The mesh was cut to size and placed through the trocar. A single-channel gastroscope with an endoscopic atraumatic grasper was used for grasping sutures. Further fascial sutures were placed every 5 cm. RESULTS: Mesh repair was feasible in all 7 animals. Mean operative time was 133 minutes. Technical difficulties were encountered. No gross contamination was seen at the time of necropsy. However, 5 animals had positive mesh cultures; 7 had positive cultures in the rectouterine space in enrichment broth or on direct culture. CONCLUSION: Transvaginal placement of synthetic mesh to repair a large porcine hernia using NOTES is challenging but feasible. Future studies need to be conducted to develop better techniques and determine the significance of mesh contamination.

Natural orifice transluminal endoscopic surgery: where are we going?

The foundation for natural orifice transluminal endoscopic surgery (NOTES) is to access the peritoneal and other body cavities through the wall of the alimentary tract via natural orifices, with the goal of performing procedures within the peritoneum and other cavities, without the need to make incisions in the abdominal wall. We have made great progress in the field of NOTES since the publication of the White Paper in 2006. There are still major fundamental goals as outlined by the Society of American Gastrointestinal and Endoscopic Surgeons/American Society for Gastrointestinal Endoscopy joint committee that need to be evaluated and answered before NOTES is ready for widespread clinical use. These include prevention of infection, instrument development, creation of a multitasking platform, and the ability to recognize and treat intraperitoneal complications such as hemorrhage and other physiological adverse events. In response to this need, recent abstracts and papers have focused on the management of intraoperative complications. The next phase is to focus on controlled prospective multicenter clinical trials that compare defined NOTES procedure to standard laparoscopy. The goal is to produce reliable and convincing data for the United States Food and Drug Administration, insurance companies, the physician community and the general public. At the present time, we still have many important milestones that still need to be met. Most investigators agree that a hybrid technique and not a pure NOTES practice should be advocated until devices can meet the current and new challenges in this field.

Transvaginal cholecystectomy by using a prototype flexible clip applier.

BACKGROUND: Currently, no endoscopic clips have been proven to be effective in ligating the cystic duct in natural orifice transluminal endoscopic surgery (NOTES) hybrid cholecystectomy. OBJECTIVE: To determine the safety and feasibility of a prototype endoscopic flexible clip applier, which is the only flexible device that deploys a zero-gap clip. DESIGN: Pilot study in a survival porcine model. Necropsy was performed at 2 weeks postprocedure. SETTING: University of Missouri animal laboratory, Columbia, Missouri. INTERVENTION: Transvaginal cholecystectomy was performed on 6 survival pigs using the NOTES Toolbox 1.0. MAIN OUTCOME MEASUREMENTS: Safety and feasibility of the described instrument. Investigators were asked to fill out a standardized, blinded questionnaire on the ease of use and functionality of the flexible clip applier. RESULTS: Clipping of the cystic duct was achieved with the flexible clip applier in all 6 pigs. The mean time for completion of clipping of the cystic duct was 9 minutes. Multiple attempts were required to successfully fire the clip in 2 of 6 pigs. We were unable to visualize the tip of the clip before deployment. Difficulty releasing the clip from the applier once fired and challenges in clip loading were encountered. The clips were visualized in place at necropsy, with no bile leakage, evidence of infection, or injury to surrounding structures seen in any cases. LIMITATIONS: Preclinical animal model. CONCLUSION: The prototype flexible clip applier showed adequate safety and was feasible in clipping the cystic duct in all animals. Design efforts to improve clip visualization, loading, and release are underway.

Pilot data on the endoscopic placement of covered metal stents to treat gastrojejunal leaks in a porcine model.

BACKGROUND: Placement of stents may be an alternative option to treat gastrojejunal (GJ) anastomotic leaks after Roux-en-Y gastric bypass (RYGB) surgery. The aim was to evaluate the performance of a covered metal stent (Alimaxx-E, 18 x 100 mm) across a GJ leak in a porcine model. METHODS: In eight pigs, a RYGB was performed and a 1-cm leak was created. A retrogastric and anterogastric GJ was performed equally with four pigs in each group. Stents were placed across the GJ anastomosis using endoscopy and fluoroscopy. The endpoints were position of the stents, healing of the leak, and complications at necropsy. RESULTS: Stent placement was feasible in all pigs it was attempted. In the retrogastric GJ group, pigs without stents survived 2 weeks without complications. Two pigs with stents died on postoperative days (PODs) 4 and 5. In the anterogastric GJ group, one pig with one stent survived 2 weeks with healing of the leak but with stent migration into the Roux limb. The remaining three pigs died between PODs 4 and 6. Pressure necrosis of the Roux limb caused by the distal end of the stent was found in all. CONCLUSIONS: Placement of fully covered metal stents is feasible. The use of small pigs with a thin small bowel wall in combination with relatively large stents was most likely the reason for complications found in all stented animals. Further studies of GJ leaks using these stents will require larger pigs or a different species.