Kitty spayed or not???

Question
I have two totally indoor kitties.  Sadie is almost 5 years old and Olivia is about 3 years old.  Both were spayed once they hit about 7 or so months of age.  Sadie is fine, but all of a sudden, Olivia is acting like she's in heat!  None of the incessant yowling yet, but she seems headed that direction.  Why would a cat do this if they have been spayed for over two years now?  

Answer
HI Julie,

I'm not sure what symptoms Olivia is showing that are like being in heat - maybe you could follow up with that info. It is possible for there to be a small amount of ovarian tissue tear off and get left behind during the spay, and even a small amount of tissue can produce enough hormones to cause a cat to act like she is in heat. However usually this shows up within a few months of the spay. Since it has been a couple years, you should have her to the vet for a complete checkup, there are many things that could cause a hormonal change, including adrenal gland tumors. Consult with your vet about the symptoms and have a full blood panel run to check out her kidne and liver function.

I assume you have checked to make sure none of the cat food you are feeding contains wheat gluten or could be contaminated with melamine, the symptoms in cats have been pretty diverse and I worry about anyone mentioning behavior changes at this time if they feed any foods made at Menu Foods.