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Common Causes

Causes are listed in order from most common to least common.

• Urinary tract infections (bladder infections) are by far the most common cause of bloody urine. They occur in dogs and cats of both genders and any age. Bladder infections may be accompanied by house soiling, straining to urinate, or increased frequency of urination.
• Crystals in the urine or stones in the bladder or kidneys occur in some pets. The symptoms of bladder crystals and stones may be indistinguishable from those of bladder infections.
• In cats, inflammation of the bladder and urethra (the tube connecting the bladder to the outside world) can occur. Especially in male cats, this syndrome can be very dangerous.
• Problems with the external genitalia may cause blood to appear in the urine.
• Masses and tumors of the bladder are very rare causes of bloody urine. Bladder masses and tumors primarily occur in elderly pets.
• Animals that cannot clot their blood may develop bloody urine.  This may occur if they have consumed rat or mouse poison.
• An animal who has suffered a traumatic event such as being hit by a car may have bloody urine.
• Animals suffering from an urgently life threatening condition called immune-mediated hemolytic anemia (IMHA) may have urine that appears bloody (but in fact does not contain actual blood cells).

Recommended Course of Action

Animals with bloody urine should be seen by a veterinarian immediately. This is true even if blood has been noticed in the urine only once. Any condition that causes bloody urine may pose a serious threat to the affected pet's health.

Copyright © Eric Barchas, DVM All rights reserved.
The contents of this page are provided for general informational purposes only. Under no circumstances should this page be substituted for professional consultation with a veterinarian.