I had my bitch booked in to the vets for spaying. Unfortunately, they cancelled her op due to one vet being ill and rescheduled for 2 weeks later. However, the day before this, she came in to season and therefore, could not be spayed that day. Her season has now been ended for a fortnight and I have noticed some mammary swelling tonight. She has not been in contact with any dogs I am aware of. She does go to the dogwalker three times a week but he knew she was in season and kept her on the lead (apparently!). He only walks one other dog, a castrated male, done 2 years ago. I was wondering about a false pregnancy, but the literature I have seen seems to suggest this would happen much later, around the time she would be getting ready to give birth. She has no other symptoms. Any advice?

hi

A false pregnancy can look exactly like a real one from very early on. If you are sure she hasnt been with a male then she will be ok. You could double check with the dog walker but sounds like a falsy to me :o))

Wendy

How old is she, and how many seasons has she had already? You need to mark down when she has seasons so that the vet can know when the right time is to spay her. I had a bitch at first season show larger nipples and a little bit of 'fullness' in the rear teats, however this did pass and she never had any other signs of a falsie. I knew she could not be pregnant. She still has slightly larger nipples than she did before her first season. If you are concerned in any aspect of her general health, seek the advice of your vet, would be the advice I would give you. :)

The ideal time for spaying is mid way between seasons - I am surprised your vet was willing to operate so close to her season, and he should not operate if she is having a phantom. You should now wait about 3 months

surprised your vet was willing to operate so close to her season

This is what made me wonder if it was the first season, as some vets will spay before the first, or if not if this bitch has an established pattern of seasons, it being odd that a vet would spay as you rightly say, so close to a season.

My girl gets phantom pregnancies, sometimes so much so she "delivers" a litter of stuffed toys. 
One time, just after we got her, she went into a false.  (kinda funny story, but scary at the time).  My sis kept saying that she wanted Cas to be bred to this shih tzu in the complex.  Mom kept saying no, of course, and that was that.
Well a few weeks later, she looked really big.  She had milk and everything.  Mom took her to the vets, worried because even though she told my sis that she couldnt mate Cas to this male dog, she was afraid she did.  (my sister is mentally disabled, so you can tell her something, but it doesnt sink in sometimes)
The phantom was so realistic, the vet couldnt tell if she was pregnant or not!  She felt sometime that felt like horns! 
Got a scan done to be sure, and it said she wasnt.  Boy were we happy!  The dog was on a No Breed at the time, until Championship, so if she was bred, the original breeder could have taken her back! 

About the spaying, it does seem odd that the vet wants to do it so close to a season, without some medical emergency (like Pyo) to warrent it being done so close.