Could she still be in heat after being spayed?

Hi everyone,

I’m posting this because I’m a bit worried about my dog.

To give you some quick background: she’s a 5-year-old Griffon that we adopted from a rescue centre just over 3 weeks ago.

Just over a month ago, the rescue centre had her spayed by one of their affiliated vets.

For the past few days, she’s been showing signs that look a lot like she’s in heat: a swollen vulva, some bleeding, changes in her behaviour and body language, etc.

I took her to the vet on Wednesday, and they think it’s either cystitis or a kidney stone, but definitely not her being in season.

We started her on antibiotics on Wednesday evening.

For the last two days, my other dog—an entire male—has been acting differently towards her. He’s been all over her, and she’s snapped at him twice in the last two days (which hasn’t happened once since she arrived).

Today she still has some discharge, though it’s not bloody this time.

I’m still having my doubts about the diagnosis (even though I really trust this vet).

Despite her being recently spayed, it really does look like she's in heat. It’s very strange.

Since this morning, she’s been keeping to herself; she doesn't seem to be in pain and doesn't have a fever.

My question is: has anyone else experienced this? Can a dog still go into heat shortly after being spayed (perhaps due to residual hormones that will eventually fade)? Could the spay surgery have been incomplete? If so, could that trigger a heat cycle even though she’s been 'done'?

I’m going to give it a bit more time before contacting the vet again.

Thanks in advance for any feedback.

Have a good Sunday!