An exam of the female genitalia and pelvis, known as a pelvic exam, is needed to diagnose a prolapsed bladder. A bladder that has entered the vagina confirms the diagnosis.
For less obvious cases, your doctor may use a voiding cystourethrogram to help with the diagnosis. It's a series of X-rays that are taken during urination. The doctor may also test or take X-rays of different parts of the belly to rule out other possible causes of discomfort or urinary difficulty.