Surgical repair and reconstruction of a nasal fistula following intra-lesional formalin injection

A 6-year-old Cleveland Bay mare was referred to the University of Liverpool Equine Hospital for repair of an iatrogenic nasocutaneous fistula. The fistula had developed following attempted ablation of an epidermal inclusion cyst located in the right nasal diverticulum with intra-lesional formalin 6 weeks previously. Subsequent tissue necrosis resulted in the formation of a full-thickness defect in the overlying tissues and the creation of a 5 × 5 cm nasocutaneous fistula. Surgical management consisted of initial debridement of the fistula and use of a commercial dermal regeneration mesh to bridge the defect, acting as a tissue scaffold. The levator labii superioris muscle was utilised to cover the scaffold by transecting it close to its proximal origin and reflecting it rostrally. Finally, a transposition skin flap was created adjacent to the site and was rotated to cover the defect. The mare made an excellent recovery, and follow-up confirmed complete healing of the surgical site with an excellent cosmetic outcome.