Poor Sadie continues to go into heat. Thanks for your help. It is best to do these surgeries when the cat is exhibiting signs of estrus, if possible. The ovarian tissue will be easier to find then because the developing egg makes it larger. If there is any question about whether or not a real estrus period is occurring, examination of vaginal smears and hormonal testing may help to confirm what is going on.
Vaginal smears are easy for most veterinary practitioners to do and to interpret fairly reliably.
Even though this is a much more involved process it may be warranted in this case, since no ovarian tissue was found on the first exploratory surgery. The normal gestation period in cats is 63 to 66 days. I was told she was six weeks old. I was planning on having her fixed, but now I will have to wait. She is an outdoor cat and it is very hard now to keep her in the house.