Common Conditions

I have female pug 4 yrs old. I got her spayed last year. Few months discharge was coming from her vulva. I got her scanned. There was no stump left. But struvite crystals were there. Doctor prescribed dog food for struvite crystals and antibiotic therapy was given as urine infection was there. Few days back we say discharge again and uti was again present and antibiotic therapy was started again. Today I again saw discharge. Is is UTI or something else?