I'm a 78 year old male with blood in my
What might cause that?
Many possible explanations
There are many possible explanations, e.g. tumor, infection, kidney stone, strenuous exercise, kidney disease, excessive intake of beets, etc. What you should do is see your doctor for a urinalysis, physical examination and referral to an ultrasound and cystoscopy. If you have no other symptoms, e.g. pain, weight loss, it is likely benign.
Hope this helps. Please let me know if you have further questions.