ASSESSMENT OF AN EX VIVO BOVINE LARGE BOWEL ENDOSCOPIC SUBMUCOSAL DISSECTION (ESD) TRAINING MODEL: OBSERVATIONS, PROBLEMS ENCOUNTERED AND SUGGESTED REMEDIES.
Dasuni Niyagama Gamage*1, Neil Mitra1, Carl Winkler1, Jaspreet Sandhu2, Erica Pettke1, Abhinit Shah3, Xiaohong Yan1, Vesna Cekic1, Shantha Kumara HMC1, Nipa Gandhi1, Richard L. Whelan1
1Surgery, Mount Sinai Roosevelt Hospital, New York, NY; 2Surgery, Brookdale Hospital Medical Center, Brooklyn, NY; 3Topiwala National Medical College, Mumbai, India
Introduction: ESD is the gold standard for sessile colon adenomas. In Japan, before colon cases, trainees do 40-60 human gastric ESD cases. Gastric ESD training in the West is not feasible. Learning colonic ESD in humans is a dangerous, challenging, and lengthy approach (case volume dependent). An alternative is to use ex vivo tissue. The authors rely heavily on an ex vivo bovine large bowel model which utilizes harvested but intact colon/rectum/anus; mucosal "lifts"? can be generated, insufflation is required, and perforation is a risk. Doing many bovine cases allows trainees to develop a resection strategy. However, the use of dead tissue is a challenge and there is a learning curve for this model. This poster will critique the bovine model and suggest solutions to model related problems.
Methods: Intact bovine large bowel is harvested soon after sacrifice. The bowel is mechanically cleansed and refrigerate the colon until use. The long colon is placed on a peg board and held in place with rubber bands. The location of the tattooed "polyp"? can be varied. A pediatric colonoscope, sclerotherapy needle, electrosurgical generator, bovey pad, lift solution, and needle knife are used to carry out ESD. The resected disc and colon wall defect are inspected post removal. Case duration, quality of resection, and deep wall injuries noted.
Results: To date, 32 bovine colons have been used for ESD training. As a result the ESD/EMR clinical completion rate has increased from under 40% to 78%. Spring clips occlude the bowel proximally. The intact anus usually maintains pneumocolon, but, if needed, plastic zip ties around the distal bowel can be used. During early cases it was often difficult to maintain a "lift"? because of poor tissue integrity (leakage from mucosal tears) which makes ESD very difficult. Histologic evaluation of colon lifts revealed rapid mucosal degradation; gut bacteria are a likely factor. The following steps delayed decomposition and improved lift quality; rapid mechanical cleansing, antibiotic solution instillation, refrigeration at all times, and use within 4-6 hours. The external colon should be kept moist during ESD. The above measures facilitated ESD. Of note, the bovine large bowel diameter was notably larger vs humans; this makes it harder to keep scope tip and adjacent shaft tangential to the polyp (critical for ESD). Colon diameter can be reduced by placing large plastic spring clips along the bowel wall.
Conclusion: The ex vivo bovine model allows many ESD cases to be done within a limited time period. Although more realistic than other models, lift maintenance is a problem due to rapid mucosal degradation; large diameter colons and air leakage are also problematic. Remedies to these problems are; bowel cleansing, antibiotic use, refrigeration, spring clip application, zip ties, and ESD within 4-6 hours.
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