There is absolutely no reason to withhold this information from a
Urologist; not only does patient confidentiality protect your privacy, but a
Urologist (especially) will need to know any alterations made to your manhood if he or she is to perform a proper evaluation and make an accurate assessment.
I suppose if you were going to your Primary Care for a routine check up, and the topic isn't brought up, it probably isn't a big deal you choose not to solicit the information (especially if you aren't having any health issues down there), but the likes of a
Urologist who specializes in examining the penis ought to know for your (and your health's) sake.