Hi, Tony. I've had "gross hematuria" twice since surgery 3 years ago. Each time I went in quickly to see my uro. He followed up with a cystoscopy and even some imaging of the kidneys, as well as the standard urine test, all of which proved negative. At his office, there was no sign of blood on either visit.
Very strange, but it hasn't happened now in well over a year, and my wife and I both theorize I may have passed a small kidney stone.
In any case, it's a symptom that should not be ignored. Stay on top of it.