For past 2 years ive been having burning sensation occasionally during start of the urination but no other symptoms. However last week I've had a drop of blood coming out of urethra after urination. I went to see an urologist and everything is clean (urine tests, ultrasound, sperm sample). I however don't have any blood in urine only 30 seconds after urination and that happened only once or twice. Does someone know something about this?