I am very sorry for your loss.
I don't know that I can fully answer your questions but I will try to help out. It is difficult to try to help give answers when I was not there to see the patient and I do not have the patient file. I am assuming she was diagnosed with a complete urinary obstruction which left the bladder 'ten times' of normal size and unable to urinate; then after euthanasia - urine began to leak. Correct??
If a complete urinary tract obstruction was present then the loss of all muscular and neuromuscular tone might have led to leaking on a bladder that was stretched beyond belief. If the bladder had burst - it would have been internal and little to no urine would have leaked out. If a stone moved away or she was just really, really, really, really 'holding' it in - there would have been a flood of urine... not leaking but almost all of the urine in this 10x sized bladder. Thus the description seems to support a complete urinary obstruction.
One of the questions that remains is why was the urine obstructed? If there had been a stone in the urethra as there had been in the kidney - why was this not mentioned? Was it not there? This would raise the suspicion of a possible TCC or transitional cell carcinoma or cancer of the badder wall. This might explain why an obstruction was present, no visible stones in the bladder or urethra, etc.... Hard to say. A necropsy (pet autopsy) would be necessary.
It sounds like you loved her very much and she had some very serious health concerns. While I cannot give you exact answers, there is nothing here that makes me think that you made a wrong decision. It sounds like you made a very hard decision in the best interest of a close friend that was relying on you. I do not think you let her down in any way. God bless.
