Spayed cat behaving like she is in season

[That old chestnut]

I have a two year old female cat who was spayed at 7 months. For the first year or so she was fine, but about 4 months ago she started calling and behaving as a cat would in season. It only went on for a couple of days so didn't worry. It has started again. She is calling constantly and is doing the whole bum in the air routine and rubbing herself backwards against everyone (including guests - slightly embarrassing). She doesn't usually go out; we discourage it and she is not really interested, but the other night she shot out the door and didn't come back for 18 hours. We did get a new male kitten last year who was castrated quite early on and he is showing no interest in her. Could this somehow be linked to her behaviour? I took her to the vet and she confirmed that she has definitely been spayed and it quite puzzled. She said although she has heard of cases like this, she has never witnessed any. Possibly a tiny bit of ovarian tissue has remained inside?
I don't know what to do for the best. Is it worth an exploratory operation which obviously comes with risks, or do we just leave her and hope it improves?

 

[touchstone]

It does sound as if there must have been some tissue left behind, I suppose further surgery would depend on how distressing you and the cat are finding it. I know there are medications that bring them out of heat, but I think they may carry their own risks.

I think I'd be inclined to see how long it lasts and if it reoccurs.