Swelling around the genitals in a female rat

Question
Hi

I keep two female rats, both about 18 months old. One of my girls has developed swelling around her genital area. It's soft, and feels almost like fatty tissue. The whole surrounding area is swollen, but her actual genitals look normal. As with most ratty problems, it started slowly but seems to be accelerating. I took her to the vet yesterday, but he was completely stumped. He said the closest thing he could think of was descending testicles, but she's 18 months old! He's almost sure it's not a tumour, because it's so soft and malleable.

I'm taking her back tomorrow, once the vet's had a chance to do research, but I thought it couldn't hurt to ask here too, as I've found useful information in your answers to others' questions. My vet has quite a lot of experience with rats, but he's not a specialist in exotic animals, so anything you can suggest would be helpful!

I don't know if this information is useful, but she's never been bred, and she has had antibiotics quite often, as she's prone to myco flare-ups.

Thanks

Julia

Answer

Its more than likely infection. Just recently I had a reader write in who had a female with  something like what your rat has, but over a period of time, the skin began to break down and ulcerated, as a mass from under the skin slowly erupted. Just from photos I knew it was a tumor that had abscessed. The mammary tumor started to abscess when it was still small.  
Swelling often indicates infection. I would put her on 10 days of baytril. If after 3 days there is no improvement,switch to trimeth sulfa. Push fluids too. Right now she is probably coming to the end of her menses and when this occurs, hormone levels rise like crazy.  Due to  the   rise in hormones, this   fuels the growth an developed.  For more info, please  refer to my page, sandyscittercity.com and go to the page on tumors.  Also if you can snap a photo that would help me alot. I know you like your vet, but if you would like, I can find names of Vets that have a   better qualified Vet. This way,you have another Vet to use for second opinion.