What does bladder is unremarkable mean?

It means ..: It usually means its normal. It also means the organ, in this case the bladder, is unremarkable as visualized on the specific modality under question. It also means the interpreting radiologist didn't see anything abnormal for him or her to comment on. Its usually a good thing.

Unremarkable Normal: Unremarkable is a medical term describing normal. There is nothing to report. It is a common phrase with exams, scans, xrays and labs.