Formation of Vesicovaginal Fistulas in Laparoscopic Hysterectomy with Electrosurgically Induced Cystotomy in Female Mongrel Dogs

Objective: The aim of this pilot study was to investigate the relationship between various types of laparoscopic bladder injuries and vesicovaginal fistula formation in an animal model.

Study Design: Sixteen female mongrel dogs were divided into four groups. All animals underwent a laparoscopic hysterectomy. Those assigned to group 1 sustained a 1-cm bipolar cautery injury to the bladder base without perforation of the bladder mucosa. Animals in group 2 had two sutures of 2-0 polyglactin placed to incorporate the full thickness of the bladder wall and the vaginal cuff. The bladder injury to group 3 was a 1-cm bladder base laceration induced with monopolar cautery, repaired with two interrupted 2-0 polyglactin sutures. Group 4 underwent a bladder base cystotomy similar to those in group 3, with the closure incorporating the anterior vaginal wall. Animals were killed and necropsy was performed at least 28 days after surgery. The bladder and vagina of each animal were harvested en bloc. Evidence of a vesicovaginal fistula was determined by two methods: transurethral injection of indigo carmine solution under direct visualization and air injection during underwater submersion.

Results: The four groups were comparable with regard to postoperative weight changes. No mongrels showed signs of infection or sepsis. Inspection of the harvested bladder and vagina revealed no fistulas in groups 1 and 2. One mongrel from group 3 and one from group 4 had evidence of a vesicovaginal fistula. With 95% CIs, the fistula rate would be at least 2% and as high as 38% if a larger study had been undertaken.

Conclusion: The female mongrel is the first identified animal model of vesicovaginal fistula formation. In this setting, an electrosurgically induced cystotomy and repair of the bladder during the performance of a laparoscopic hysterectomy is associated with the formation of postoperative vesicovaginal fistulas.