Anytime there is blood in the urine of an animal especially a male (smaller urethra than female) it's time for a vet visit ASAP!
Possibilities can include Urinary Tract Infection, Urinary/Bladder Crystals or Stones or something more serious.
Avoid biting when a simple growl will do
The Spirit Lives As Long As Someone Who Lives Remembers You - Navaho Saying
Vindication ~ For all those pets who became sick or lost their lives from tainted pet food