Ovarian remnant syndrome
Ovarian remnant syndrome in dogs is defined as the presence of functional ovarian tissue in a previously ovariohysterectomized bitch.
This syndrome is an iatrogenic condition rather than a spontaneous pathological disorder. The mechanism of the syndrome was first described in 1970, where ovarian cortex could be functional if implanted elsewhere in the abdomen rather than in its anatomical origin.
The cause of this syndrome is usually the presence of remnant ovarian tissue left in the abdomen following ovariohysterectomy as a result of improper placement of clamps or ligatures, poor visualization of the surgical field, or revascularization of a piece of ovarian cortex dropped into the abdomen during surgery. Ectopic ovaries have not been reported as a cause in the dog, unlike the cat, where this is relatively common.
The right ovary in dogs is affected significantly more often than the left ovary and concurrent hydrosalpynx, paraovarian cysts and teratoma or luteoma are common. These animals had a significantly longer intervals between ovariohysterectomy and diagnosis of remnant syndrome than did dogs without neoplasms.
Clinically affected dogs usually present with signs of estrus, including vulvar swelling, bloody vaginal discharge and behavioral changes, such as flagging. Some animals may even allow copulation, but they do not become pregnant.
These symptoms may become evident up to 3 years after the original ovariohysterectomy.
A presumptive diagnosis can be established with vaginal cytologic evaluation, abdominal ultrasonography, resting hormone assays, hormone challenge testing with gonadotropin releasing hormone and exploratory laparotomy with biopsy.
An estradiol concentration of > 20 pg/mL can be considered as evidence of ovarian remnant syndrome, but it is not thought to be as reliable as progesterone measurements. Progesterone should be measured when the bitch is showing signs of estrus or within 50 to 80 d after that with a level > 2 ng/mL indicative of functional corpora lutea. A hormone challenge test can be used if a progesterone level of < 2 ng/mL is found, or the animal is presumed to be in proestrus. Progesterone levels should increase to > 2 ng/mL by 1 wk following the injection of human chorionic gonadotropin or gonadotropin releasing hormone.
A commercially available human-based assay is also available for measurement of anti-Müllerian hormone concentration in dogs.
A definitive diagnosis is made by exploratory laparotomy and histological confirmation of the presence of ovarian structures in conjunction with resolution of the signs.
- University of Guelph
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