Canuck1973, welcome. I have not had this problem but, I have close experience through my wife and other friends. For openers, almost 30 years ago she was passing blood to where did all of your tests including a retro grade pylogram that looks further up into the kidneys. We never found a cause, and her hematuria also subsided. I also have had two other friends that intermittently pass blood over a longer period with no known reason. Beyond kidneys stones, UTI, weak arteries in the affected area there are a host of other reasons. Some long distance runners and bikers get this. Sorry this isn't more definitive but, sometimes is does happen.
DX 5/6/2008 TAG3 papillary tumor .5 CM in size. 2 TURBS followed by 6 instillations of BCG weekly with a second round of 6 after a 6 week wait.
I am a 45 yr male. In 2015 had large amount of blood in urine. It went away in five weeks. Had CT scan and scope all come back negative. Blood came back five weeks ago, another scope and ultrasound both came back negative. There was mention that my bladder is rich in blood vessels and most likely a blood vessel rupture, but could not see it on scope. Had blood work, all normal.
Did not have another CT scan as I had one four years ago. If still bleeding in three months, probably another scope and perhaps a CT scan.