What Causes Recurrent UTI And Cystitis?

my daughter is 23 on low dose antibiotic for 4 yrs has had numerous uti,s and when a urologist looked in here bladder cycos tipi said it looked and compared to 70 yr old did a biopsy and was not cancer or autoimmune thre was a band of infection looking infection all around after nearly 4 yrs it cleared up except for one spot so doc did 2nd biopsy and burnt it cauterized it that was 6 months ago daughter went went for another cycos tipi a few days ago infection looking spot with bacteria growing on it is back right above the burned off. cystis is what they are calling it doc says he hasn t seen a case before like this acts like infection but doesn t clear up or respond like one hasn t said ic wonder if that could be it but doesn t look like ic images on the internet.