I had a ultrasound of my bladder and kidneys and the report said "unremarkable scan" but it said "under-distended bladder" so would they see that ok?

Most likely OK: An under distended bladder on an ultrasound does not denote a problem. More often pathological lesions are better visualized on ultrasound when the bladder is full however. If the ordering physician is concerned about a potential bladder lesion (tumor, stone, blood in urine, etc.) then cystoscopy should be performed by a urologist regardless of what the ultrasound shows.

It depends: How under distended the bladder was and what your clinician was looking for. If your doc was looking for things like bladder outlet obstruction, an undistended bladder pretty much rules that out. If they are looking for things like bladder wall thickening, a collapsed bladder might make that impossible to see. But if the bladder is at least partially distended, usually the scan is ok.