i have tjis kind of problem too and thankfully it was relatively short lived most of the time i have the opposite problem of urgency but i was sent to a Continence Nurse for assessment and she was able to do a very simple ultra sound pre and post peeing to see how much residual urine was in my bladder post peeing. Not only can retained urine lead to UTI but it can also lead to reflux back up towards the kidneys where it can do serious renal damage. I now see the Continence Nurse at least yearly for a check just to be sure that my residual volumes are not increaing