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A New Focus on a Challenging Problem: Development of a Porcine Rectovaginal Fistula Model

A New Focus on a Challenging Problem: Development of a Porcine Rectovaginal Fistula Model

Presenting Author(s)

Danielle N. Westenberg, MD (she/her/hers)

Urogynecology Fellow
Mayo Clinic
Rochester, Minnesota, United States

Co-Author(s)

TS

Tiffany Sarrafian, DVM, PhD

Large Animal Surgeon, Research Associate
Mayo
Rochester, Minnesota, United States
RM

Ryan Mahlberg, M.S., HTL

Senior Research Technologist
Mayo Clinic
Rochester, Minnesota, United States
PS

Paul G. Stalboerger, PMP

Program Manager
Mayo Clinic
Rochester, Minnesota, United States
ET

Emanuel C. Trabuco, MD

Associate Professor
Mayo Clinic
Rochester, Minnesota, United States
ED

Eric J. Dozois, MD

Colon and Rectal Surgeon, Professor of Surgery, Chair, Division of Colon and Rectal Surgery
Mayo Clinic
Rochester, Minnesota, United States
AB

Atta Behfar, MD, PhD

Professor of Medicine
Mayo Clinic
Rochester, Minnesota, United States
John A. Occhino, MD, MS (he/him/his)

Director, FPMRS Fellowship; Associate Professor
Mayo Clinic
Rochester, Minnesota, United States

Objectives: Rectovaginal fistulas (RVFs) are a challenging structural abnormality to treat, often requiring multiple surgical interventions. Research into novel therapies for RVF treatment are currently limited by lack of a sizeable and accurate animal model. The porcine vaginal epithelium and surrounding musculature correlate well with human vaginal anatomy, and the porcine rectal epithelium, lamina propria and muscular layers are comparable to human rectal anatomy. Therefore, pig specimens are a preferred model for pelvic floor disorders. The objective of this study is development of a feasible and reproducible RVF model in pigs.

Methods: Eight female pigs underwent rectovaginal fistula creation and were divided into four groups of two animals each: (1) a 2.54 cm (1 inch) circular defect made with cautery alone, (2) cautery with placement of a 2 mm seton, (3) cautery with placement of a 2.54 cm (1 inch) stainless-steel gauge, (4) compression necrosis between dual 2.54 cm (1 inch) magnets. Fistulas were examined under anesthesia at 6 weeks for measurements and photographic documentation. Animals were sacrificed between 12 to 14 weeks. The primary outcome of this study was fistula patency. Secondary outcomes were fistula size and histologic appearance of the fistula tract.

Results: There were no infections or complications related to the fistula creation in any of the groups. One animal in the cautery alone group was euthanized at 12 weeks due to a non-RVF related foot condition. Two methods of fistula creation reliably resulted in a patent fistula in both animals at time of euthanasia: cautery alone and cautery with stenting using a stainless-steel gauge. The average fistula diameter was 1.9 cm (0.75 inch) in the cautery alone group and 4.1 cm (1.6 inch) in the gauge group. Only one patent fistula in the magnet group (7 mm, 0.28 inch) was noted at the time of sacrifice. There were no visible fistulas in the seton group. Patent fistulas all demonstrated epithelialization of the fistula tract on histology.

Conclusions: This study demonstrates two safe, feasible and reproducible methods for creating an RVF model in a porcine specimen. Porcine RVF models may be used to investigate novel rectovaginal fistula therapies.