Canine Ovarian Remnant Syndrome

(Estrus after Ovariohysterectomy)


  • Signs of 'estrus' after ovariohystectomy

    • Swollen vulvua - common

    • Vulvar discharge - common

    • Attracting male dogs

    • Signs of pseudogenetra or pseudopregnancy 2 months after the episode of 'estrus'


  •  Has an ovariohysterectomy been performed?

    • History - how long has the dog been owned

    • Known ovariohysterectomy?

    • Where?

    • Who? - It can happen to specalaists!

  • Are there other sources of estrogen?

    • Exogenous


  • Ovarian remnant left at surgery - faulty technique?

  • 17% of post ovariohysterectomy complications in one study were due to ovarian remnants.

  • May be anomalous accessory ovarian tissue in the broad ligament


  • 15.5 months average post surgery (3 months to 5 years)

  • Mean interestrus interval 8.8 months


  • Vaginal cytology - should be cornified cells if there is any estrogenic stimulation endogenous or exogenous).

    • If there is an ovarian source, estrogen should decline and cornification subside in 9-20 days

    • If the estrogen is exogenous, the cornifcation will subsist.

  • Progesterone - Progesterone should be high for approximately 2 months after the signs of estrus regress if there is an ovarian source of estrogen.

    • Submit a blood sample for progesterone around 2 weeks after estrual signs end.

    • There should be a 'normal' luteal period if an ovarian remnant is present.

  • LH testing - Löfstedt RM, Vanleeuwen JA. Evaluation of a commercially available luteinizing hormone test for its ability to distinguish between ovariectomized and sexually intact bitches.  J Am Vet Med Assoc. 2002 May 1;220(9):1331-5.

    • Ovariectomy results in loss of negative feedback on LH (via GnRH?) resulting in a rise in fast and long term rise in LH.False positive occur if the bitch is at the natural LH peak.

    • Normal LH is 'low'. 


    • Single high serum LH concentration was not a reliable indicator of ovarian removal 

      • Sensitivity (98%) but moderate specificity (78%) because of a high frequency of false-positive test results (actual LH peak)

    • A single low serum LH concentration was an excellent indicator that a bitch was sexually intact.

    • The LH test results were positive within 10 days after ovarian removal

    • Remained high in bitches from which ovaries had been removed > 5 years previously.

    • Excellent agreement in test interpretation within and among evaluators and over a 6-hour time span.

  • Ultrasound

    • Hard for most to identify ovaries (need to scan repeatedly over time to identify. See it in the picture below?

    • Follicles may be seen on ovaries.

    • Corpora lutea do not always appear hyperechoic

    • 11/12 scanned (21 total in study) in one study had suspected ovaries (JAVMA 236:548-551, 2010)

      • 9/12 correctly identified (presence or absence)

      • 3/12 remant found at surgery, but not seen by US

  • Treatment - Surgery

    • Location

      • 6/21 - left pedicle

      • 13/21 - right pedicle

      • 2/21 - both pedicles

Other sources of estrogen

  •  Exogenous

    • Topical estrogen creams and sprays used by menopausal women

      • Can pass estrogen to dog, and is becoming more common

      • Usually small breed dogs that are carried around

      Click on the any picture above to see a web article on Evamist

    • Ingestion of any estrogenic substances - do a complete inventory of household products

  • Endogenous estrogen production


  • Remove exogenous estrogen if documented

  • Surgery

    • Document that the presence of an ovarian remnant is highly likely

    • Best done in diestrus - less blood than in 'estrus'

    • 35% had bilateral ovarian remnants at the pedicle

    • 46/46 dogs with problems had remnants in the ovarian pedicle (extreme exploration probably not needed)

  • JAVMA study

    • 6/21 - left pedicle

    • 13/21 - right pedicle

    • 2/21 - both pedicles

    • Submit sample for histopathology

    • If luteal tissue is present on the removed remnant, false pregnancy may occur




contributed by Bruce E Eilts on 25 September 2012


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