I posted a picture of my pregnant mare on the Pregnancy thread and a pic of her edema between her front legs. I didn't want to hijack that thread so I thought I would post the pics here so you could see what a large pitting edema looks like. These edemas can appear on heavy mares and larger breed mares - or mares having large foals but not always. My vet has seen them as large as footballs and in different places on the mare's abdomen, and says they are often present in big milkers. They can look really scary and awful but they are not normally a danger to the mare and usually go away pretty quickly after foaling.
They can be confused with a hernia, or an infection/abscess or hematoma. It is called a pitting edema because when you press on the edema, an impression (pit) remains of your hand/finger where you pressed. It feels pretty firm at first, but squishy when you squeeze it - like that "slime" stuff you get in joke shops.
The mare is a large 17hh maiden TB and the pics were taken on day 317. She started to make a bag at 9 months and I love her even though she is cranky.
Will post more if changes happen.