Thank you for answering the question--though it appears I didn't provide you with enough information. Two doctors-my regular vet, and an internal medicine specialist thought it was a clot. A cardiologist, and a surgeon who both looked at the tail and detected a slight pulse below the swollen purple area at the base of the tail thought it still might be an injury. After sending me home with instructions to watch for sepsis and necrosis, I took McGee in to the regular vet to check the tail, twice,-- the surgery was going to be later in the week. He died in horrible pain with what appeared to be paralyzed back limb(s) before that could happen. My vet seemed to feel that the original diagnosis was probably correct, and he threw another clot. There was no way to tell for sure--even necropsy--which after an already high vet bill was cost prohibitive. I was told that there were diseases such as certain cancers,accute pancreatitis, lymphomas etc where hemorrhaging and clotting can occur, although it did appear that too much time had passed for it to be DIC.
I was looking for a fresh outlook, and some empathy. The answer you gave me was honest and direct based on the information I gave you. Telling someone the loss of their best friend was "bad luck", well...