Bladder fistula is diagnosed with an x-ray study. The type of x-ray used may be a CT scan or a pelvic x-ray. A dye that shows up well in x-rays (called "contrast") will be put into your bladder, either through a vein or a catheter. Your health care provider may also look into your bladder with a cystoscope, a long, thin telescope with a light at the end. In some cases, x-ray studies with contrast may be done on other organs (like the bowel), as well.