Bone marrow aspiration is a procedure in which a doctor uses a needle to draw a small sample of liquid marrow from inside a bone, usually the back of the hip, to examine how blood cells are being made. Its main clinical indications are unexplained abnormal blood counts, suspected leukemia or other blood cancers, staging and monitoring of known disease, and some infections and storage disorders. Recent advances such as flow cytometry, next-generation sequencing, and powered needle devices have made the sample far more informative than a microscope slide alone.
What Bone Marrow Aspiration Involves
Bone marrow is the soft, spongy tissue inside larger bones where red cells, white cells, and platelets are produced. It fills the marrow cavity, and in adults the most productive marrow lies in the pelvis, spine, breastbone, and ribs.
An aspirate is a liquid sample that shows individual cells in detail. It is usually paired with a trephine biopsy, a small solid core of bone and marrow taken through the same skin incision. The aspirate shows what the cells look like, while the biopsy shows how full the marrow is and how the cells are arranged. Together they give a complete picture.
The procedure is a core tool across hematology and oncology. For billing and coding details, see our guide to bone marrow aspiration CPT codes.
Clinical Indications
A marrow examination is ordered when blood tests show a problem that cannot be explained from the blood alone. The table below lists the most common indications.
| Indication | Typical question the sample answers |
|---|---|
| Unexplained anemia, low white cells, or low platelets | Is the marrow failing, infiltrated, or producing abnormal cells? |
| Suspected acute or chronic leukemia | What type of leukemia is it, and which genetic changes does it carry? |
| Myelodysplastic syndromes | Are there dysplastic cells, excess blasts, or characteristic mutations? |
| Multiple myeloma and related disorders | What proportion of the marrow is abnormal plasma cells? |
| Lymphoma staging | Has the lymphoma spread to the marrow? |
| Aplastic anemia | Is the marrow empty (hypocellular), and why? |
| Fever of unknown origin | Is there an infection such as tuberculosis or leishmaniasis in the marrow? |
| Response monitoring | Has treatment cleared the disease, and is residual disease detectable? |
Signs that often lead to referral include tiredness from anemia, frequent infections, easy bruising, unexplained weight loss, or abnormal cells on a blood film. Our overview of abnormal blood conditions covers many of these findings. Many hematological disorders cannot be diagnosed with certainty without a marrow sample.
Safety checks before the procedure
Aspiration is safe even in most people with very low platelet counts. Doctors still review clotting results, blood thinners, and any history of bleeding disorders, because some patients need a clotting factor or medication adjustment first. Skin infection over the planned site is a reason to choose another site.
How the Procedure Is Done
- Positioning: the patient usually lies on their side or front so the back of the hip bone (the posterior iliac crest) can be reached. The breastbone is an alternative site for aspiration in adults, and the shin bone may be used in infants.
- Local anesthetic: the skin and the surface of the bone are numbed. Some centers also offer light sedation.
- Aspiration: a hollow needle is passed into the marrow cavity and a small volume of marrow is drawn into a syringe. Many patients feel a brief, deep pulling sensation at this moment that anesthetic cannot fully block.
- Biopsy: if needed, a slightly larger needle takes a core sample.
- Aftercare: pressure and a dressing are applied. Most people go home the same day with simple pain relief.
The whole process usually takes under half an hour. Serious complications such as significant bleeding or infection are uncommon. In my practice, explaining the pulling sensation in advance makes a noticeable difference to how patients experience it.
Sometimes no liquid marrow can be drawn, called a dry tap. This itself is informative, because it often points to scarring of the marrow (fibrosis) or marrow packed with abnormal cells, and the biopsy then becomes essential.
What the Laboratory Looks At
A single aspirate can be split for several tests:
- Morphology: smears are stained and examined under the microscope. The pathologist assesses the balance of cell lines and counts blasts, which normally make up less than 5% of marrow cells. Iron stains show iron stores and ring sideroblasts.
- Flow cytometry: identifies cells by the proteins on their surface, which is key to classifying leukemias and lymphomas.
- Cytogenetics and FISH: detect chromosome changes such as translocations that define specific diseases.
- Molecular testing: looks for gene mutations that guide diagnosis, prognosis, and targeted therapy.
- Microbiology: cultures for infections when fever is unexplained.
These results feed directly into treatment. For example, specific genetic changes in acute myeloid leukemia influence the choice of therapy, and the cellularity of the marrow in aplastic anemia helps decide between immunosuppressive treatment and transplantation.
Recent Advances
Next-generation sequencing (NGS) panels can test many genes at once, refining diagnosis in myelodysplastic syndromes and acute leukemias and identifying mutations that can be targeted with specific drugs. Highly sensitive measurable residual disease (MRD) testing by flow cytometry or molecular methods can detect tiny amounts of leukemia after treatment, helping guide decisions about further therapy.
On the procedural side, powered drill devices can make biopsy faster and may improve sample quality in some settings. Imaging guidance helps when targeting a specific area of bone, and digital pathology allows slides to be reviewed remotely. For more on marrow biology and disease, see our bone marrow guide.
Frequently Asked Questions
Does bone marrow aspiration hurt?
The local anesthetic numbs the skin and bone surface, so most people feel pressure rather than sharp pain. The brief pulling sensation during aspiration is the most uncomfortable part, and mild soreness for a day or two afterwards is common.
How long do results take?
Initial microscope findings are often available within a few days. Genetic and molecular tests take longer, commonly one to several weeks, depending on the tests requested.
What is the difference between aspiration and biopsy?
Aspiration draws liquid marrow to study individual cells, while a biopsy removes a small solid core to assess marrow structure and cellularity. They are usually done together in one sitting.
Can I drive home afterwards?
If you had only local anesthetic, many centers allow it, but having someone accompany you is sensible. If you received sedation, you should not drive for the rest of the day.
Key Takeaways
- Bone marrow aspiration samples liquid marrow, usually from the back of the hip, and is often paired with a biopsy.
- Key indications include unexplained cytopenias, suspected blood cancers, staging, and response monitoring.
- Modern testing adds flow cytometry, cytogenetics, and NGS to microscope review.
- It is a short, safe outpatient procedure with a low complication rate.
