Bone Marrow (cont.)
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Why are bone marrows done?
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Most bone marrows are performed to diagnose various conditions that affect the different types of blood cells. Abnormal blood counts can lead a doctor to suspect that there may be a problem in the bone marrow. Another frequent purpose of a bone marrow is to diagnose certain cancers or to determine the extent of the cancer (cancer staging) within the bone marrow. Bone marrow procedures can also detect uncommon conditions, both cancerous and non-cancerous including abnormal proteins (such as in amyloidosis), inflammation (such as in sarcoidosis), and infection (such as in tuberculosis). This procedure can also be used to obtain marrow for transplantation.
What bone is used to sample the bone marrow?
The most frequent site for obtaining bone marrow is the pelvic bone, known as the ilium. A portion of this bone is readily accessible in most people from the lower back and is usually marked by shallow dimples on either side of the spine. Other sites include the front of the pelvic bone near the groin and the sternum at the front of the chest.
How is a bone marrow performed?
Typically, only a local anesthetic is required to numb the skin and tissue down to the surface of the bone. A small cut (less than one-quarter inch) is then made in the skin. A hollow needle whose center is filled by a removable metal rod called a trochar is used to penetrate through the dense outer shell of bone. Once inside the bone, the trochar is removed and a syringe is attached to the now hollow tube of the bone marrow needle. The bone marrow is withdrawn as a thick liquid by pulling back on the plunger of the syringe and collecting the liquid. This sample is known as the marrow aspirate. This part of the procedure only lasts a few seconds, but is usually the most painful due to the sudden sense of a negative pressure inside the bone.
A biopsy can also then be obtained in addition to the marrow aspirate or when an aspirate cannot be obtained. The same needle is used but without the center portion in place. As the needle is partially rotated into the bone it cuts a core which is trapped inside the needle. Once the needle is removed, this core can be extracted from the needle barrel. This core can then be prepared with fixatives and stains for examination under a microscope.
Since the skin cut for a bone marrow procedure is usually very small, no stitches are generally necessary and only a bandage is applied.
Medically Reviewed by a Doctor on 2/10/2014
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