31 Aug 2015
Stephen Robertson
Job Title
Figure 2. Testicles attached to a bifurcating uterus.
Keira may look like your average Staffordshire bull terrier, but we discovered she was very far from average.
She registered with the practice for her first vaccines at eight weeks old and received a clean bill of health. When she was four months old, she presented with a mild fever and a purulent vaginal discharge. It was noted she had an unusual firm polyp type vaginal protrusion.
She was a little young for a typical vaginal polyp, but we discussed spaying and thought we could examine the lump more thoroughly under general anaesthetic. A course of antibiotics was prescribed for the discharge, which cleared up uneventfully.
We next saw Keira for spaying when she was six months old and got a bit of a surprise. Out popped a pair of what looked like normal testicles where the ovaries would be situated. There was an epididymis-type structure clearly visible on the surface and the testicles were attached to a normal, but very small, uterus, which terminated in a normal bifurcation and cervix.
The vaginal protrusion was easily palpable and extended along the floor of the vagina for roughly three to four inches. It felt like a hard cylindrical tube and we presumed it to be an enlarged clitoris or os penis.
The testicles were sent for histology. They consisted of numerous seminiferous tubules, but with no evidence of the germinal layer or spermatozoa production. On the periphery of these was epipidymal tissue. Only male gonadal tissue was present in the sections examined, so Keira is a male pseudohermaphrodite. We would need chromosome determination to confirm this though.
The expectation is she would have an XY chromosome pairing and that there has been an abnormality in the development phase. The Y chromosome carries the sex determining gene (SRY). Its absence means ovaries develop, so we can assume the SRY gene is present in this case. Phenotypic sex is determined by the gonads after differentiation.
The testicles produce Mullerian inhibiting factor and testosterone, which stimulate the pathways for male characteristics. Testosterone is converted to dihydrotestosterone (DHT), which promotes the formation of the prostate, urethra, penis and scrotum. Without DHT, the external genitalia will be feminine. So, the assumption was Keira had either failed to produce, or respond to, these hormones, resulting in the female karyotype.
Since neutering, we have had no further problems with Keira’s health so no further investigations or tests are deemed necessary. Our only real concern is the vulval protrusion and the possibility it could lead to problems with vaginitis and urinary tract infections in the future. Only time will tell.
