When is a bladder not a bladder?

My  patient, 10 y/o German Shepard Dog, came in with the complaint  of incontinence. She was wetting her bed at night, something she had never done. With some extra questioning I found that she had been "off" for weeks with decreased appetite and weight loss. On exam I felt something large in her belly so I called for radiographs and saw this:

On the left side is a large round area that looks like a very large urinary bladder. I asked my technicians to walk her outside and let  her pee and she did a lot. But after she came back from the yard a second view looked the same. What was going on? In this case Ultrasound gave me the answer. Sadly, this is a very large abdominal tumor leaning on her urinary bladder. That is what was making her urinate at night. Sometimes it takes multiple tests to get the right answer.