Ovarian Remnant Syndrome
Ovarian remnant syndrome is a complication of ovariohysterectomy. It occurs when a portion of ovarian tissue is left in the abdomen - either because it is not properly removed in the first place, or because it is accidently dropped back into the abdomen during surgery. The remnant ovarian tissue may be very small or ectopic, but it can revacularise and continue to produce hormones, resulting in oestrus. It is possible for clinical signs not to develop until several years after the original ovariohysterectomy surgery.
Clearly the condition is only seen in neutered females. It can occur in both the cat and the dog, but is most commonly seen in the bitch - particularly in the right ovarian pedicle as this is hard to access during surgery.
Affected bitches continue to show signs of oestrus. These signs include the production of a serosanginous vulval discharge, swelling of the vulva, sexual attraction to male dogs, and standing to be mounted. The gap between oestrus cycles is variable.
Alternatively, dogs may present as systemically unwell as a consequence of stump pyometra.
Differential diagnoses include vaginitis, neoplasia, urinary tract disease, mechanical and chemical irritation and rarely, bacterial or viral infection.
A provisional diagnosis may be made based on the history and clinical signs. The following tests may be performed to confirm this diagnosis:
Vaginal smears should be taken during oestrus to confirm diagnosis.
It should demonstrate epithelial keratinisation, small intermediate and large epithelial cells, erythrocytes and no polymorphonuclear leucocytes. These signs are caused by an increase in plasma oestrogen levels.
Serum Progesterone: Elevated levels of serum progesterone concentrations two weeks after the animal has demonstrated signs of oestrus is proof of retained luteal tissue.
Serum Oestradiol: Elevated levels of serum oestradiol are suggestive of the condition. It is important to glean from the history whether the animal is receiving any exogenous hormones as treatment for urinary incontinence for this test to be of value (as this will also raise oestradiol levels).
Dynamic testing: Human chorionic gonadotropin/gonadotropin-releasing hormone can be used to induce ovulation. If remnant ovarian tissue is present the levels of serum progesterone will rise, whist oestrogen levels drop. This is a useful technique in cats.
Adjuncts such as ultrasonography and CT can be used to locate remnant tissue (particularly ovarian cysts).
Laparoscopy and laparotomy can also be used to definitively diagnose and treat the condition.
Curative treatment is removal of the remnant ovarian tissue by laparotomy. The ovarian tissue may be very difficult to identify if the animal is not in oestrus, therefore the operation should be performed in or around oestrus. However, as the tissue is very vascular at this point, accurate haemostasis is necessary to prevent the complication of haemorrhage.
Following the successful removal of remnant ovarian tissue, prognosis is very good.
|Ovarian Remnant Syndrome Learning Resources|
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|Small Animal Abdominal and Metabolic Disorders Q&A 11|
Merck & Co (2009) The Merck Veterinary Manual (Ninth Edition), Merial
Tennant, B (1999) Self-Assessment Colour Review Small Animal Abdominal & Metabolic Disorders Manson
Tivers, M & Baines, S (2010) Surgical diseases of the female genital tract 1. Ovaries and uterus In Practice 2010;32:292-299
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