Dermoid sinus in the perirectal fossa of a Siamese cat with involvement of the vaginal wall.

A 2.5-year-old spayed female Siamese cat was presented with a recurrent exudative wound in the right perirectal fossa. Clinical examination at presentation revealed a 1 cm long open wound with purulent discharge in the right perirectal fossa but was otherwise unremarkable. A computed tomography contrast-enhanced study showed a tracking sinus which could be traced from the right dorsolateral perianal region right up to the level of the vagina. Surgical exploration was performed from the perirectal region. The intermuscular sinus tract, which formed a cystic structure and connected to the vaginal wall, was en bloc excised. Histopathological examination confirmed the diagnosis of a dermoid sinus in the perirectal fossa with vaginal infiltration. To the authors' knowledge, this is the first case report in the veterinary literature of the successful surgical management of a dermoid sinus in the perianal region connected to the vaginal wall in a cat.