Ovarian Tissue Detection

Oestradiol (E2)
Oestradiol may be used to detect the onset of oestrus in females or to detect ovarian tissue in spayed females. A single sample may only be required if the animal is showing signs of oestrus at the time of sampling. In spayed animals it may be necessary to do a GnRH or hCG stimulation test to stimulate any ovarian tissue to produce E2. Males with suspected sertoli cell tumours should be screened with E2.

GnRH Stimulation Test

  1. Take a basal blood sample.
  2. Inject i/v 0.32 μg Buserelin (Receptal®; Intervet SP). A very small volume of drug required (80μL) therefore it is advisable to dilute the drug 1:10 with sterile water for injection and then inject 0.8mL.
  3. Take a further blood sample 3 hours later.
  4. Label tubes clearly and request Oestradiol.

Interpretation

Males and females in anoestrus should have undetectable (<10.0 pmol/L) levels of E2. Ovarian activity or abnormal testicular activity will result in increased levels of E2.
Sertoli cell tumours in male dogs normally produce significant levels of oestrogens.
Each case must be carefully assessed and interpretation given according to clinical history.

Canine hCG Stimulation Test

  1. Take a basal blood sample.
  2. Inject i/v 200 – 500 IU hCG (Chorulon®; Intervet SP).
  3. Take a further blood sample at 90 – 120 minutes
  4. Label tubes clearly and request Oestradiol.

Interpretation

Males and females in anoestrus should have undetectable (<10.0 pmol/L) levels of E2. Ovarian activity or abnormal testicular activity will result in increased levels of E2. Sertoli cell tumours in male dogs normally produce significant levels of oestrogens. Each case must be carefully assessed and interpretation given according to clinical history.

Canine hCG Stimulation Test

  1. Take a basal blood sample.
  2. Inject i/v 200 – 500 IU hCG (Chorulon®; Intervet SP).
  3. Take a further blood sample at 90 – 120 minutes
  4. Label tubes clearly and request Oestradiol.

Interpretation

Basal oestradiol levels should be <10.0 pmol/L.
Levels greater than 10.0 pmol post hCG are suggestive of ovarian remnants.

Feline hCG Stimulation Test

This test is reported as being more effective at detecting ovarian remnants in queens. Testing should be done between one and three days after the onset of oestrous behaviour. The administration of hCG is to induce ovulation.

  1. Take a basal blood sample (do not use serum gel tubes).
  2. Inject i/m 500 IU hCG (Chorulon®; Intervet SP).
  3. 7 days later take a further blood sample (do not use serum gel tubes).
  4. Label tubes clearly and request Progesterone.

Interpretation

Basal progesterone levels should be <3.0 nmol/L.
After 7 days progesterone levels increase significantly above 3.0 nmol/L and often >15.0 nmol/L in queens with ovarian remnants. Luteal tissue may be easier to see at exploratory surgery.