Objective: To identify the blood supply to the vulval fold and adjacent skin, and evaluate it as a transposition flap for closing perineal wounds in dogs. Study Design: Prospective study. Animals or Sample Population: Five female canine cadavers and 2 cases referred for excision of mast cell tumors adjacent to the vulva. Methods: Dissection was performed to identify the vascular supply to the vulval fold in two cadavers following arterial injection of red latex and methylene blue, respectively. In three cadavers, barium sulfate mixed 1:1 with water was injected into the terminal aorta. The vulval fold and surrounding perineal skin was excised and radiographed. Transposition flaps using the vulval fold and adjacent skin were used to close skin defects in two dogs presented for wide excision of mast cell tumors situated ventro-lateral and dorso-lateral to the vulva, respectively. Results: The vulval fold and adjacent skin was perfused bilaterally by branches of the ventral perineal and external pudendal arteries, which entered dorsally and ventrally, respectively. As incisions used to create a transposition flaps from the skin surrounding the vulval fold transect these vessels, the flap is dependent on the sub-dermal plexus for survival. There was 100% survival of transposition flaps in the 2 clinical cases and healing proceeded uneventfully with acceptable cosmetic and functional results. Conclusions: The vulval fold and surrounding skin can be used as a subdermal plexus flap to close large perineal defects in dogs. Clinical Relevance: Availability of a defined local skin flap will improve treatment of diseases resulting in large perineal skin defects in female dogs.
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