Urethral polyps are found with a cystoscope. A cystoscope is a long, thin telescope with a light at the end that lets your urologist look inside the body. This is performed under anesthesia in children. However, the key test to diagnose benign urethral lesions is a voiding cystourethrogram (VCUG). VCUG is a type of x-ray test. VCUG uses a special dye infused into the urethra to show the structures.