Females that show oestrus signs after has been spayed are included in this syndrome named Ovarian Remnant Syndrome (ORS). Is a condition specially embarrassing for the veterinarian that has done the surgery; a surgery that is routine and secure, as is a condition in which the ovarian tissue is incompletely removed during ovariectomy or ovariohysterectomy. Usually are bitches or queens with clearly signs of oestrus: male attraction, vulval hemorrhagic secretions, vulval swelling, comportamental changes, all of them typical of oestrogen activity, but in occasions this oestrogen activity is no so hard, and if the owner has not the ability to detect it, will not be discovered.
In human medicine, the ORS is assumed to be a secondary condition after surgery on an inflamed ovary, causing the deposition of ovarian tissues on surrounding organs (peritoneum and serosal surfaces). However in small animal practice this is not the cause as is a routine surgery with no pathological changes in the ovaries. In the bitch, ovarian tissue remaining after an incomplete ovariohysterectomy becomes cystic and may be the cause of recurrent oestrus. Is more frequently localised in the right ovary than in the left, this fact has been relationed with the anatomical position of the right ovary more cranial and dorsal. A uterine stump pyometra is possible if at the same time the surgeon has left a uterine horn or uterine body. In the queen, this condition is more frequent when the procedure has been done through a flank incision. In cat surgery the surgical midline approach permits a easy location of the ovaries with less difficulty of identification than in the dog female. But in the queen more case reports has demonstrated the presence of ectopic ovarian tissue in the ovarian pedicle, although in a few reports such tissue has reported in the omentum or abdominal wall. This condition is thought to develop during embryonic development where the ovaries do not experience a complete migration from its original localisation as success in the male testis, finding remnants of ovarian tissue very far from the ovary.
A numerous experiments has demonstrated the possibility in cats and dogs to implant ovarian tissue in the omentum or stomach serosa, with subsequent ovarian activity (hormonal determinations).
In contrast to other species, in companion animals, the excessive production of estrogens from the adrenal glands sufficient to induce oestrus symptoms, has not been described.
The clinical signs are typical of oestrus, as vocalisation, treading behaviour, vulvar swelling, male attraction, vulval hemorrhagic discharge, pseudopregnancy, mating posture and others in a female previously spayed.
After good anamnesis and clinical suspicion, the clinician has two ways to demonstrate ORS, the vaginal cytology and hormonal assays.
The vaginal cytology of a spayed female is typical of anoestrus, with a low cellularity of basal and parabasal cells and some leucocytes and a mucous background. If the female is exhibiting signs of a ORS we can repeat the cytology every 2 to 3 weeks to confirm the anoestrus or a oestrus induction. To confirm a ORS is necessary a proestrus-oestrus (follicular phase in the queen) or diestrus cytology in a previous spayed patient. In the queen, the follicular phase is characterised with a clear background, superficial acidophilic cells (squames the majority) and no red blood cells. In the bitch, the proestrus and oestrus phases are consistent with more or less red blood cells, more or less leukocytes, and a predominance of intermediated and superficial acidophilic cells. Another possibility to confirm a ORS is a diestrus cytology with presence of different cell types, parabasal, intermediate, superficial and white blood cells.
The hormonal assays are more expensive and time consuming. We can detect serum estrogens or progesterone to confirm ovarian activity with or without ovulation or oestrus induction.
A lot of conditions can be confused with a ORS. We must rule out vaginitis, urinary diseases (urinary tract infections), exogenous estrogens, and behavioural alterations especially in the queen.
Medical inhibition of oestrus can be done, but if we castrated the animal before, this option is no easy explained and in some way ethically contradictory. At the same time if in the initial surgery we have left a piece of uterus we can induce a uterine stump pyometra. For this reason we don't recommend this option.
The surgical approach is the best option in this case. We do a second surgery with mild ventral laparotomy when the oestrus signs are presents, this permits a more easy visualisation of the ovarian remnant tissue thanks to the increased vascularization. In the other hand, this increase in vascularization prone to haemorrhage. Surgery in diestrus is another option, but it can induce pseudopregnancy in the bitch. We must inspect both pedicles looking for a revascularization just caudal to both poles of the kidneys. Any suspicious tissue should be excised and submitted for histopathological study to confirm diagnosis.
1. Wallace, M.S.: The ovarian remnant syndrome in the bitch and queen. Vet. Clin. North Amer.; Small Anim. Pract. 21 (May 1991) 501-517.
2. Wallace, M.S.: Ovarian Remnant Syndrome, in Current Veterinary Therapy XI, ed. R.Kirk, W.B. Saunders Philadelphia, p. 966-968.
3. Prats, A.: Ovarian remnant syndrome in the queen. EVSSAR newsletter. Volume 4 n°1, July 2001.