I had bladder cancer in 2000. Treated as outpatient. No chemo. I noticed blood in my urine yesterday morning. Saw my internist at 11:45 AM. Gave me a referral to see a urologist, next Thursday. At 2 pm, same day, I checked my urine, which was clear of any blood . Subequent urine samples show no traces of any blood. I am 88 years old and ride the stationary bicycle for 30 minutes daily. I also had ba ck surgery for spinal stenosis about two years ago. What is the probable cause of the blood and should I still see the urologist and undergo a cat scan and other tests.