A bone marrow biopsy is the extraction of a piece of bone marrow for microscopic examination. Bone marrow is the soft material that lines the cavity of bones and is primarily found in the center portion of bones. It is not found in the ends of bones. Its chief purpose is the production of red and white blood cells and platelets. The blood cells stay in the marrow until they are mature, and then are released in the bloodstream. When fighting off infection the bone marrow will produce more white blood cells. If the body has lost blood (due to bleeding, for instance), the marrow will produce more red blood cells.

What Does a Bone Marrow Biopsy Reveal?

Microscopic evaluation of the bone marrow will reveal signs of disease and can be used to measure the effects of therapy or treatments. Specifically, the tissue removed will be studied for abnormalities involving the formation of red and white blood cells and platelets and to determine if malignant cells are growing. For instance, bone marrow disease may be present if red and white blood cells fail to mature properly, within the marrow. A biopsy can also help determine the presence of malignant cells, which indicates cancer.

How Is a Bone Marrow Biopsy Performed?

Prior to performing a bone marrow biopsy, the patient is sedated or anesthetized. In general, a large biopsy needle is inserted into the patient's bone until it reaches the bone marrow, and a small piece of the marrow is sucked in (aspirated). The needle is then withdrawn and the marrow is placed on a slide.

The biopsy can be done with the animal in a number of positions, depending on the site to be aspirated. The common sites for aspiration include the ribs; the bone of the upper forelimb (near the shoulder); the hip bone; and the thigh bone.

The needle is inserted through the skin until it reaches the bone. Once in contact with the bone, the desired site for penetration is determined and the needle is pushed through the bone into the marrow cavity. Decreased resistance indicates that the needle has entered the cavity. A syringe is attached to the needle and a piece of marrow is sucked in. The needle and syringe are then removed from the bone. The syringe is disconnected from the needle, and the extracted material is deposited onto glass slides for staining and examination under a microscope. The procedure itself takes about a half hour to perform.

Is a Bone Marrow Biopsy Painful?

Yes. The insertion of the needle into the skin and through the bone causes discomfort. As with people, the pain experienced from the needle and the extraction will vary among individual animal.

Is Sedation or Anesthesia Needed for a Bone Marrow Biopsy?

A local anesthetic is used to make the passage of the needle through the skin less painful. A general sedative or general anesthesia is often given to relax the patient entirely, unless the patient is severely weakened or debilitated.