Blood in the urine should always be investigated.
Cancer, infection, or a kidney stone are all possibilities. You can consider a CT scan or ultrasound to evaluate for stones, or a cystoscopy to evaluate the bladder for any possibilities of masses.
Even if it was a one-time incident, this should be discussed with your personal physician or urologist.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Kevin, M.D.
http://www.straightfromthedoc.com