Case 5: Heat behavior in a spayed cat

CASE 5: Heat behavior in a spayed cat

Case Information:

A 4-year-old spayed female Himalayan is presented to your clinic for abnormal behavior. The cat is urinating out of the litterbox, rubbing against the owner and yowling repetitively for about 5 days every 2 to 3 weeks. The owner is concerned her spayed cat may be showing signs of heat.

You see the cat one week after it began showing the behavior described above. The cat is normal on physical examination. The vaginal cytology specimen below was collected. Serum progesterone was 0.6 ng/ml.

Question: Are these results normal or abnormal? Is this cat in heat?

Answer: This is normal for a spayed cat. These are non-cornified vaginal epithelial cells. The most likely rule-outs are ovarian remnant syndrome and behavior that appears cyclic because a stimulus is perceived periodically. You decide to try to diagnose the former. Remembering that cats are induced ovulators, you know measurement of resting progesterone is not a useful diagnostic test. What will you do to diagnose ovarian remnant syndrome?

Ovarian remnants that are functional produce estrogen. To identify estrogen secretion in this cat, you could try to measure estrogen in serum but estrogen concentrations, even when as high as possible, are still measured in only picograms / ml. Collection of a vaginal cytology specimen when the cat is exhibiting the suspicious behavior is best. see the cat when she is exhibiting the behavior and collect the vaginal cytology specimen below.

These are cornified cells. The cat has estrogen in her system. At this point, you could (1) explore the abdomen, looking for the ovarian remnant(s) containing follicles, or (2) induce luteinization of the follicles with gonadotropin releasing hormone (GnRH). Check serum progesterone concentration two weeks after administration of GnRH. If serum progesterone is greater than 2 ng/ml, one or more ovarian remnants containing luteal tissue are present.

Case outcome:

GnRH was administered at the time the above cytology was collected. Two weeks later, serum progesterone concentration was 5 ng/ml. Exploratory laparotomy revealed remnants of ovarian tissue at both ovarian pedicles.