THE RABBIT AS A MODEL FOR VAGINAL SURGERY

P. Drewes, S. Marinis, R.A. Word, M.A. Nihira

University of Texas Southwestern Medical Center at Dallas, Dallas, TX

OBJECTIVE:  Controversy exists regarding the optimal approach for the vaginal repair of pelvic floor defects.  Lack of an animal model to compare different surgical strategies limits comparative trials of different techniques and graft materials.  Rabbits are unique among mammals in that a significant portion of their vagina, the vestibule, projects externally beyond the pubic bone.  This characteristic affords accessibility unequaled even in some larger mammals.  We explored the feasibility of using the rabbit as a model for vaginal reconstructive surgery.

MATERIALS AND METHODS: Dissection of the posterior vaginal epithelium and rectovaginal septum was performed on 36 parous breeder New Zealand white rabbits.  The animals were anesthetized with mask inhalational isoflurane.  The initial animals received 48 hours of postoperative intramuscular narcotics for analgesia.  Dimensions of the vestibule, the duration of the surgeries, and postoperative complications were recorded. The costs of acquiring and maintaining the rabbits were compared with those of other common research animals.

RESULTS: The average length of the vestibule was 4.57 cm. The average anteroposterior diameter was 1.48 cm and average outer transverse diameter was 1.25 cm.  Two to three centimeters of rectovaginal septum could be easily exposed for dissection.  The mean rabbit weight was 4.8 kg.  Routine surgical instruments were used without the need for magnification.  The mean duration of surgery was 37.5 minutes, and mean time under anesthesia was 61.3 minutes.  There were no intraoperative complications.  At the suggestion of the animal handlers, we reduced the postoperative analgesia from 48 to 24 hours.  The rabbits were followed for a minimum of six weeks postoperatively.  Two rabbits had a suspected postoperative wound cellulitis that responded well to intramuscular injections of penicillin G.  At our institution, rabbits cost $120.00 to acquire, compared with $205.00 for a sheep, and $200.00 for a 50 lb. dog.  The per diem costs for maintenance of a rabbit in our animal resources center is $1.71, compared with $9.64 for a sheep, and $11.67 for a dog.  Another advantage of the rabbit is that there is a potential to breed one’s own colony.

CONCLUSION:  The New Zealand white rabbit is an excellent model for some aspects of vaginal surgery.  Rabbits are significantly less expensive to obtain and maintain than larger mammals such as sheep or dogs.  They are relatively easy to anesthetize.  Additionally, vaginal surgery is well-tolerated, and can be performed on them with routine instrumentation.  Although not suitable as a training model, the rabbit could prove useful in studying surgical techniques and grafts in the posterior vaginal wall.

Key Words: animal model, vaginal surgery, New Zealand white rabbit

Disclosure - Grant/Research: M. Nihira, Cook Ob/Gyn; Speakers Bureau: M. Nihira, Pfizer, Yamanouchi Pharma America, GlaxoSmithKline; Advisor: M. Nihira, Yamanouchi Pharma America, GlaxoSmithKline.