MEDICAL PROCEDURES
Bone Marrow Aspiration And Biopsy
What is bone marrow?
The soft material in the center of bones is the bone marrow. In some bones, the bone marrow consists only of fat. Other bones contain what is termed cellular marrow. The cellular marrow has different types of cells that give rise to red cells, white cells and platelets. The marrow may also contain abnormal cells that are not usually present, such as cancer cells. Since the production of red cells requires iron, the marrow is one of the places in the body that normally stores a supply of iron.
What is a bone marrow procedure?
A bone marrow procedure (commonly referred to as a bone marrow or bone marrow aspiration) is a technique used to obtain the blood-forming portion (marrow) of the inner core of bone for examination in the laboratory or for transplantation. The bone marrow consists of inserting a special needle into a bone that contains marrow and withdrawing the marrow by suction or coring out a sample of the marrow.
Why are bone marrows done?
Most bone marrows are performed to diagnose various conditions that affect the different types of blood cells. Another frequent reason is to diagnose certain cancers or to determine the extent of the cancer (cancer staging). 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 (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 special needle is used to penetrate through the dense outer shell of bone. Once inside the bone, the center portion of this needle (the trochar) is removed and a syringe is attached. The bone marrow is withdrawn by pulling back on the plunger of the syringe and collecting the liquid.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 stimulation of small nerves inside the bone.
A biopsy may also 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 twisted through 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.
Since the skin cut is usually very small, no stitches are generally necessary and only a bandage is applied.
What is done with the bone marrow sample?
The bone marrow core biopsy is first placed in a liquid that keeps the cells in their natural condition (fixative solution). The sample is then placed in a solution to soften the bone and is finally processed like other biopsies in the tissue study (histology) laboratory. The liquid portion of the bone marrow is spread on glass slides and stained to make the bone marrow smears. The slides are then examined under the microscope, usually by a specially qualified technician or physician such as a hematologist or pathologist.
Portions of either sample may be submitted to the microbiology laboratory for cultures. Certain conditions may require other specialized studies such as genetic testing or cell marker studies.
What diseases are diagnosed by bone marrow examination?
A wide variety of conditions can be diagnosed by examination of the bone marrow. The following examples illustrate some of the most frequent conditions, but there are many more. The presence or absence of cancer in the bone marrow can determine what treatments are recommended to a patient with cancer known to be elsewhere in the body. Some cancers (leukemia, multiple myeloma) arise from cells in the marrow so this is where the biopsy must be taken to confirm the diagnosis. A low blood-clotting element (platelet count) in the blood (thrombocytopenia) can be due to several causes. It is important to establish whether or not the cells that make the platelets (megakaryocytes) are still present in the marrow (idiopathic thrombocytopenic purpura) or are gone (aplastic anemia). Most cases of anemia (low red blood cells) can be diagnosed by simple blood tests. When these tests are negative, examining the marrow can reveal problems with the red blood cells that are uncommon causes of anemia (sideroblastic anemia, aplastic anemia). Persistent fevers can be caused by infections that reside in the marrow (atypical mycobacteria, brucellosis) and a sample of the marrow may provide the best source of culture material.
What are the risks of a bone marrow procedure?
Different individuals feel the pain caused by injection of the local anesthetic and the remainder of the procedure to a variable extent. There may be dull soreness for a day or two. Significant complications are very unusual but can include bleeding, infection, and prolonged pain. Rare fatalities have been reported, usually during sternal marrows when the needle has penetrated the sternum and cut one of the arteries on the surface of the heart.
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