Dogs and cats with ovarian remnants typically show cyclic estrous behavior within 1 year of spay surgery, although signs have been reported to commence as long as 3 years post-spay. Vaginitis and cystitis need to be ruled out as potential causes of estrous-like signs.

Use of vaginal cytology alone to support the diagnosis is usually adequate, although similar changes can be caused by estrogen secreting tumors.

Vaginal cytology should be performed on smears from the anterior vagina. Preponderance of superficial cornified epithelial cells and anucleate squames indicate elevated estrogen concentrations. In cats, an important finding is the absence of noncellular debris and mucus, thereby enabling the vaginal epithelial cells to be clearly visualized.

• Test information: Submit 2 smears.
• Test code is CYTO (use the Pathology/ Cytology submission form).

Estradiol measurement is not a preferred test for diagnosing ovarian remnants. Levels are low when the animal is not cycling, and although estradiol may be elevated during estrus, levels tend to fluctuate. Elevated estrogen concentrations can be seen in animals with adrenal gland disease.

• Test code is S16295. 1 mL of serum is required.

In dogs, progesterone concentrations will be significantly elevated after ovulation and throughout diestrus. Cats are believed to be induced ovulators, so progesterone concentrations will not be elevated unless the cat has been bred or stimulated to ovulate.

• Test code is T475. 1 mL of serum is required.

Provocative testing must be done while the animal is showing signs of estrus.
Protocol:
Measure baseline progesterone concentration, then administer HCG or GnRH (Gonadorelin). With HCG, use 44 IU/kg IM or 400 IU total dose IM for dogs; and 44 IU/kg or 250 IU total dose IM for cats. With GnRH , use 2 ug/kg or 50 ug total dose IM for dogs; and 2 ug/kg or 25 ug total dose IM for cats.

Measure post-injection progesterone concentration 1-2 weeks later. A post-provocation progesterone concentration greater than 1-2 ng/mL is supportive of an ovarian remnant. However, a post-provocation progesterone concentration less than 1 ng/mL does not exclude the possibility of an ovarian remnant.

• Test code is T475. 1 mL of serum is required.

Persistently elevated luteinizing hormone concentration [LH] indicates that the dog or cat has been spayed (and LH is increased due to lack of negative feedback from the ovaries). However, as a single high result could be a normal physiologic event in an intact patient, the test should be repeated.

A low [LH] is an excellent indicator that the pet is intact.

• Test code is 16520. 2 mL of serum are required. This is a send-out test and turnaround time may be as long as 1 month.

Note: These same tests also can be used to determine whether a pet obtained from an animal shelter has been spayed.

The best time for surgery is while the animal is showing signs of estrus. Ovarian tissue can be that left behind at time of spay or can be supernumerary ovarian tissue. About 50% of cases are bilateral, although unilateral cases affect left and right sides equally.