I've had blood (invisible) in my urine for many, many years. When it was first discovered by the AME some 20 years ago he told me to see my GP who arranged for some fairly complex x-rays. These revealed nothing so it was a cystoscopy next. I was scared.... but it really was a doddle. My biggest problem was trying to convince the nurse in attendance that it was the fear causing me to look like a midget!! Job done in 5-10 mins. Urologist explained there were no stones or cancer. He said why I get blood in my urine but, basically it was nothing to be concerned about. I continued to get my Class 1 medical every until I retired 8 years ago - and I'm still here (apparently).