Any clue on what this is?

[Satana]

My first thought would be a busted blood vessel from feeding. When was the last meal and was it over sized at all?

Second possibility is a burn. Do you use belly heat or lamps?

Would I need to do anything for a busted blood vessel? I think that's possibly what it is. The last rat she got I noticed some difficulty coiling it. Is this a common thing? I've never seen anything like it before