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.

Comparative evaluation of specific methods for labeling of Encephalitozoon cuniculi in paraffin wax-embedded tissue samples.

Detection of the microsporidian Encephalitozoon cuniculi in tissue samples is considered difficult. The aim of the current study was to determine whether immunohistochemistry (IHC) and in situ hybridization (ISH) represent reliable methods for the detection of E. cuniculi in postmortem tissue samples of rabbits. Paraffin-embedded tissue sections of brain and kidneys of 48 naturally infected pet rabbits, 10 negative controls, and the eyes of 3 further rabbits were used for all investigations. By IHC in 19 animals (37.3%), spores could be clearly detected and were all equally stained. By ISH using a digoxigenin-labeled oligonucleotide probe, only 6 animals (11.8%) proved undoubtedly positive. In these cases, many parasite-like objects revealed strong typical purple-black positive signals. However, several of the examined samples showed only partial staining of the pathogen or unclear results. Thus, in order to find an explanation for these inconsistent ISH results and to take a more detailed look at the different developmental stages of the organism, electron microscopy was applied. Empty spores, which had already discharged their polar filaments, prevailed in total number. Taken together, both techniques are rather insensitive, but under the condition that sufficient numbers of microsporidia are present, IHC can be recommended for specific identification of E. cuniculi in tissue samples. In contrast, ISH failed to detect some developmental stages of the organism, and, as such, ISH is therefore considered an inappropriate diagnostic method.