How old is your dog?What breed of dog is she?Does she have any tick exposure?Are there deer in your area?
Thanks for answering my questions.
I want to make a couple quick phone calls to the vets at the clinic where I used to work (they specialize in orthopedic surgery) to see what they think...would that be okay with you?
Thanks for being patient with me. So I talked to two of the vets I used to work with and the first thing we discussed was the heart issue. They both said it's possible that your dog's murmur was so minor in the past that perhaps your vet didn't hear it on exam. As a dog ages, these murmurs can become more pronounced and then become more easily discernible. Of course, it's hard for them to know for sure, but they suspect that's what happened with your dog.
As far as the localized edema in the hip area, they both were very clear that localized edema in a singular area can be the result of injury, burns, obstructions in an artery due to something like a blood clot or even cardiac issues. The fact that your vet has found a 'new' murmur makes them wonder if the lymph glands in that area are swollen with fluid that the heart isn't able to get rid of due to compromised function. They were also concerned about the possibility of some kind of neoplasia (cancer), but agree that a mass like that would have taken some time to develop, and wouldn't have happened acutely, like it sounds like it did in your dog.
When it comes to your next step, the general consensus here is that you have a FNA (fine needle aspirate) done to test the fluid in the area. This involves taking a needle and syringe and drawing off some of the fluid in the lump and then looking at it under the microscope. Hopefully this will tell your vets (and you!) what is going on in that area. If no diagnosis can be made this way, then a biopsy is your next step. This is where they remove a bit of the tissue in that area and send it off to a lab for evaluation. They also suggested x-rays and perhaps a full cardiac work up to make sure it's not the heart that is causing this problem.
I hope this helps!!