This isn't professional advice

Suspected ovarian remnant syndrome in the bitch

Absent-mindedly leaving a bitch attached to some or all of its ovarian tissue during a routine spay could precipitate an acute episode of existential angst in the unsuspecting veterinarian. Typically, such anxiety has its onset when an owner reports heat signs several months to years after surgery. Like all errors, the pain is amplified if discovered by someone else, in the worst case, a veterinarian from a competing clinic. This brief post will discuss the clinical approach to suspected ovarian remnant syndrome (ORS) in the previously spayed bitch with focus on clinical presentation and appropriate diagnostics. 

At its onset, ORS presents similarly to a normal pro-oestrus that one would see in a fully intact bitch. Affected females demonstrate typical signs of oestrogenisation: a swollen vulva or perineum, a tail or vulvar reflex, as well as attraction to male dogs. There may be a variable degree of sanguinous vulvar discharge, depending on how much uterine or cervical tissue remains, since the blood in canine heat originates from endometrial tissue.

The easiest way to conclusively diagnose the condition, is by vaginoscopy and vaginal cytology. The presence of a variable degree of vaginal oedema (in pro-oestrus and early oestrus) and cornification of vaginal epithelium (an increase in number and density of superficial cells seen on Diff-Quik stained smear) indicates that the bitch presently has, or has recently had, exposure to oestradiol.

It is seldom useful to employ more advanced diagnostics like sex hormone profiles or ultrasonography on initial presentation. Serial vaginoscopy and vaginal cytology is most useful, but has the disadvantage in that it requires the owner to bring the bitch back every 2-3 days for follow up examinations.

Elevated anti-mullerian hormone (AMH) in a bitch with suspected ORS will confirm that gonadal tissue is present. It is used routinely by gynaecologists to assess follicular reserve in women. However, in South Africa currently, this test is not always available or affordable for veterinary use.

Serial vaginoscopy and cytology is adequate to confirm clinical ORS. Your aim with serial vaginoscopy and cytology is to confirm that the bitch is progressing through a predictable ovarian cycle. There should be a gradual decrease in vaginal oedema, seen vaginoscopically as sharpening of the vaginal folds with an increase in superficial cell index, followed thereafter by progression to dioestrus. Dioestrus can be seen vaginoscopically as small, round, pink folds. A dioestrus cytology smear has a dense population of epithelial cells of varying ages, together with bacteria and inflammatory cells. Classically, the ‘dioestrus cell’ can be seen: a neutrophil superimposed on an epithelial cell, although this is not always present and its absence does not rule out dioestrus.

Once you have confirmed by repeated vaginoscopy and cytology that a bitch has gone through all these phases of the oestrous cycle, you can be certain that she has ovarian tissue somewhere, and you need to go and find it. You can at any stage perform an ultrasonographic exam prior to surgery to try and locate the remnant ovary, but the tissue might be very small and subtle, and could be very easily missed. Not finding ovarian tissue on ultrasound exam definitely doesn’t rule out ORS. It is best to follow the bitch’s cycle into dioestrus, then go straight to surgery and try and find the remnant directly. Before performing surgery, once you have observed the bitch enter dioestrus with vaginoscopy and cytology, draw a blood sample in a serum tube for progesterone. You always want to do ORS surgery in a bitch in dioestrus, for reasons that I’ll explain shortly.

When you surgically explore the abdomen to look for the ovaries, remember that in the embryo the ovaries develop from the primitive gonad which is adjacent the primitive kidney. Usually, one can find a piece of ovary hidden in fat somewhere amongst the remaining piece of the suspensory ligament. Very occasionally, there may be accessory anatomical ovarian tissue, however this is rare: surgical error is far more common. Even rarer still are non-ovarian sources of sex hormones (functional neoplasms or dysfunction of other endocrine organs), however these will not follow the normal physiological progression from pro-oestrus through oestrus to dioestrus. Once you have removed what you believe to be the offending tissue, get the client to bring the dog back 2-3 days later for you to draw another serum sample. After putting the date on this second sample, submit your two stored serum tubes together to your laboratory of choice for serum progesterone determination. If you have removed all ovarian tissue, you should see a precipitous drop in progesterone between blood samples. A bitch in dioestrus should have high progesterone because ovarian follicles, which were previously secreting oestradiol during pro-oestrus and early oestrus, have ovulated and formed corpora lutea, which secrete progesterone. Remove all sources of luteal tissue, and progesterone disappears too. A progesterone value of anything above 5-6nmol/L suggests that there is, at the very least, some luteal tissue. A progesterone value below 2-3nmol/L indicates that no luteal tissue is present. Always try and wait for the bitch to form this luteal tissue (i.e. she must be in dioestrus) so that you can do progesterone measurements before and after surgery to be sure you removed everything. If you do revision surgery while she is still in oestrus, it is more difficult to immediately and conclusively confirm surgical success.  

I hope you found this article useful. If you did, please share it. If you have any questions or queries, please contact me. I am open to referrals and can provide a wide array of services in all our domestic species, from assisted reproduction to reproductive surgery, as well as herd or flock health and disease outbreak investigation.