Hematuria is the presence of red blood cells in the urine causing bloody urine. The causes can be from the following:
Bacterial infections of the urinary and genital tracts
Cancer of the urinary or genital tracts
Calculi (stones) in the urinary tract
Rare parasites of the urinary tract
You will need to have a vet run tests to see the underlying cause. These will be Urinalysis, Complete blood count, possible abdominal X-rays.
Treatment will of course depend on the outcome of the tests. Blood in urine is most times an infection of the urinary tract which is easily treated with antibiotics. Also diet changes can help prevent them from coming back. Hill's science diet makes a great food for urinary tract health. You can also provide cranberry juice to help with any pain due to a urinary tract infection.
Please let me know if you need any further assistance with this.