This outpatient test is most often done by a urologist in the operating room. General anesthesia is often used. The urologist inserts a long, thin telescope with a light at the end ("cystoscope") through the urethra. Then s/he places a tube ("catheter") up into the ureter. A dye is injected into the ureters through the catheter. X-rays are then taken of the ureters and kidneys. The test can take 15 to 30 minutes.