What can cause mucous in urine? had 3 utis a few months ago, resolved with cipro (ciprofloxacin). latest culture negative. had cystoscopy, seemed to be normal. ideas?

Urethra: It could be from "urethritis" if the bladder was normal. Any inflammation of the urinary tract can cause mucus in the urine called "PYURIA". If the culture is negative and you are otherwise healthy and have no other or ongoing symptoms then it is likely something to monitor and I would not worry. If there are symptoms, you may need additional antibiotic therapy, including regimens for urethritis.

Sounds like: you have had a complete and appropriate work up - mucus in urine may be normal or may indicate inflammation. You should address this to the physician who did your work up to see if tests for other infections may be needed.