Suggest Remedy For Extreme Lower Back Pains

My friend has extreme lower back pains. She has had plenty of xrays, medications, and physical therapy. All that have barely temporarily lesson the pain and no conclusion as to what it is or what it is caused by. Recently, they had thought it was kidney infection, but tested by urine it was not. She said it was because she was swelling on her lower back? and so they though it was kidney infection.
Her symptoms are lower back pains (RADIATING PAIN), hurts all the time whens shes standing up and sitting down. It sometimes makes her legs and butt hurt (that or it may be from running). She has been getting mini fevers lately. Im not sure if thats due to the pain or to weak immune system?
PLEASE HELP HER TO KNOW WHAT COULD BE AFFECTING HER.