I'm certainly no bet, but:
sounds to me like malnutrition, especially the lack of internal fat storages.They found the snake had a shrunken liver, lack of internal fat stores and and some discolouration around the gal bladder.
Peter, was this the same snake that you were having difficulties getting feeding, by chance? I know you had one that was very reluctant to feed for you.
Congrats on the negative IBD test!