Hematoma on Dogs

By PetMD Editorial on Oct. 17, 2012

Canine Hematoma/Seroma

A hematoma is defined as a localized collection of blood outside the blood vessels. A seroma is similar except that the fluid accumulation contains only serum without red blood cells being present.

Hematomas and seromas can occur anywhere in the body. Subdermal hematomas/seromas form under the skin and are probably the most commonly type of hematoma or seroma. However, hematomas and seromas can also occur within the head or brain, within other organs of the body and even on the ear (i.e., aural hematoma).

Hematomas/seromas can occur in both dogs and cats. If you would like to learn how they affect cats, please visit this page in the petMD health library.

Symptoms and Types

Symptoms will depend on the location of the hematoma or seroma.

  • Subdermal hematomas and seromas will result in a fluctuant swelling under the skin.
  • Hematomas or seromas in the head/brain can cause a variety of symptoms, including coma, seizures and other neurological abnormalities.
  • Hematomas and seromas in other organs may be asymptomatic or may cause failure or dysfunction of the organ involved.


Trauma is the most common cause of hematomas and seromas. Other causes include blood clotting abnormalities which lead to excessive bleeding.


Diagnosis of a hematoma or seroma depends on the location as well. Subdermal hematomas and seromas can generally be diagnosed by physical examination coupled with evaluation of fluid withdrawn from the lesion. Hematomas and seromas in internal organs or in the brain/head may require special imaging (X-ray, ultrasound, MRI or CT scan) for diagnosis.


If small, the hematoma or seroma may reabsorb and resolve without intervention. Larger hematomas and seromas may need to be drained by your veterinarian. In some cases, it may be necessary to place a temporary drain in the area to allow further accumulation of blood and/or serum to drain from the area.

See Also

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