Hi Likair,
I have blood in the urine which was first discovered by the Air Force when I went for a flying scholarship medical at the age of 16. I subsequently went for a check up at my local hospital where they examined my bladder and found nothing. The next time it became an issue was when I went for an interview/medical with my University Air Squadron. They sent me to RAF Halton where I had quite extensive tests culminating in a Kidney biopsy, not the most pleasant experience however they discovered that I have a condition called Iga ( can't remember what it stands for ) but basically when my kidneys filter my blood they allow some red cells to pass through ( never been visible to the eye ) and are therefore present when I pass water. So every time my urine is tested it shows blood cells being present. The Airforce did not appear too concerned and allowed me to continue flying with the UAS. It was recommended that I have an annual check up with my local hospital every year, which I have been doing for the past 12 years and there has been no change, I have still to this day never seen any blood present when I pass water. I hold a class 1 medical and currently fly long haul. The CAA have never been unduly worried, they just require my NHS doctor to sent the annual check up results for their records. The only advice I have ever received is to limit my alcohol intake and that unless I ever suffer from high blood pressure in the future this condition should never give me cause for concern.
I hope this is of help and I have not bored you too much, my advice is that unless you have felt or seen any physical characteristics not too worry, certainly in terms of keeping your medical in both the short and long term.