First off I want to say I am very sorry to hear of your loss. Such a sudden death of an apparently healthy animal must have been hard.
I can understand rushing her off to get a necropsy wasn't possible for you. I know for human females when they are 'gravid' it isn't easy to keep things down normally but to see such a shocking scene I can see your mind would be totally blown off the thought of getting a necropsy.
Trying to guess what caused her death is nearly impossible, unfortunately. At best we can make educated guesses. What may help is you give us a detailed description of your setup (temps, substrate, normal feeding habits, what you feed, how often, etc) as well as the healthy history of your dragon since you owned her. Also mention her age, was she ever bred, did she lay any clutches (fertile or infertile) etc. Was she housed alone? You did mention she was down for brumation, died you stop feeding a day or two before? What was the ambient temperature when she started to brumate?
Next, any changes to her environment and around the immediate area of her cage? Did you or anybody else spray any sort of insecticides etc? Did an apartment connected to yours get fumigated? (vents if not sealed off can allow the toxic insecticides into your home, especially with some apartment buildings and even duplexes, if they share air flow between them, either for heat or AC).
I know one poster suggested it wasn't an accidental death, or death by some previously undiagnosed condition. Is it possible something heavy fell on your dragon? Something heavy falling on your dragon could cause the appearance you have and as it thrashed about it may have managed to dislodge what fell on it. I know you didn't take a good look of the mess (as I got the impression once you saw she was dead, you didn't linger).
There are no human diseases that can be transmitted to dragons and vice versa. What that poster meant was human/animal common diseases, such as cancer, heart attacks, strokes etc. We can infect these ailments on our dragons, nor they to us. But dragons certain can get tumors, have strokes etc.
Internal bleeding can cause bloating, but so can decay. Not sure how long it takes for bloating to take effect in a corpse, but I think it must be at least 12 hours..but I can be wrong.. temperatures certainly will affect how fast cells break down and gases form. Thus the bloating may not be a cause of the death, but a secondary symptom of decay.
As you did indicate there was bile, vomiting certainly will account for the bile. Vomiting can be caused by undigested food rotting in the stomach, intestinal problems (tumers, a cyst that ruptured, internal parasites, gastronomic problems). Any number of organ failures or diseases could cause some or all of these symptoms as shown by how your dragon die.
In the end, it may be we will never know what happened. Unfortunately a necropsy was the best way for a qualified vet to determine what caused the death. It could be viral, tumor, infection, digestion issues, a severe cyst, parasites, physical injury etc. Just no way to know.
If she isn't your only dragon, as a precaution, I suggest taking the rest of your dragons in to see a qualified vet for a complete physical and blood work. This way if your first dragon died due to some disease or parasite, you can make sure your other dragons do not have it. Keep in mind that testing for adenovirus is a special procedure not normally done by standard tests.
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PHLdyPayne