Bone marrow aspiration (Bone marrow biopsy)

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• To obtain a bone marrow sample as an aid to diagnosis - either as an aspirate (cytology) or core (histopathology) biopsy.

• Aid in etiological diagnosis of non-regenerative anemias  , leukemias  , myeloma  and pancytopenias. Bone marrow aspirates provide cytologic specimens for evaluation of cellularity, eg in cases of leukemia, dysplasias and maturation defects, whereas core biopsies are useful for diagnosis of myelofibrosis, metastatic neoplasia, lymphoma, infections granuloma and megakaryocyte number, etc.
• Adjunct to the staging of neoplasms such as lymphoma .

• Not a difficult procedure.
• Samples can be obtained from several sites: wing of ileum (described here), femur and the humeral head, or proximal tibia.

• One random sample could miss focal or multifocal disease.

• Faulty technique mainly to blame for failure to collect sample.
• Selection of site optimized by use of survey radiographs to identify areas of lysis.
• Must interpret results in conjunction with peripheral blood sample .

• 15-30 minutes for sedation/anesthesia and skin preparation.

• 15-30 minutes.

• Anesthesia/sedation risk must be assessed in view of possible debilitated nature of patient.
• In many cases patient may be sick enough to require only minimal sedation for restraint.

Requirements

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• Aspirate needle - plastic handle and guide with a bevelled stylet .

• Biopsy needle - 'Jamshidi' core needles (Jamshidi bone marrow/aspirate needle, American Pharmaseal, Valencia, CA 91335; Bone marrow biopsy needle, Sherwood Medical, St Louis, MO 63130).
• Glass slides.

• Syringe.

• 10 ml syringe.
• Formalin.

Preparation

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• Clip area ~10 x 10 cm over dorsal ileum.

• Palpate the area over the dorsal surface of the ileum   .

• Stand a number (10-20) clean microscope slides vertically against a sandbag in preparation for making smears.

• Sedated or anesthetized in sternal recumbency.

Procedure

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It is often useful to follow the aspiration with a core biopsy

• Make a stab incision through the skin over dorsal surface of ileum .
• Insert the aspiration needle vertically through the muscle layers until it reaches bone .
• Drive the needle into the bone with a 'to and fro' coring motion .

• When the needle is firmly embedded in the bone, remove the stylet.
• Attach the syringe and apply sharp suction .
• A small amount of dark red marrow should well up into the syringe.
• Make multiple smears of this specimen immediately before it clots   .
• Squeeze a drop of the aspirated fluid onto each of vertical slides. This allows blood to run off slide and narrow spicules to adhere.
• Make smear by first gently tapping bottom of slide on blotting material then making crush smear with second slide dragged at 90° to first slide.
• The second slide used to make the smear is air dried and fixed.
• Remove the aspiration needle.

• Insert the Jamshidi needle through the same stab incision.
• Enter the bone at a different site from the needle aspirate, with a coring motion.
• When it is just below the periosteal surface remove the stylet.
• Push the needle into the bone to about 1-2 cm with a 'to and fro' coring motion.
• Detach the core of bone by several twists.

• A good smear should have fat spaces and spicules of dense material   .
• Air dry and send to laboratory.

Core biopsy

• Remove the needle carefully.
• Extract the bone core by pushing it from the tip of the needle toward the hub with wire.
• Fix the bone core in formalin and send to the lab fordecalcification and analysis.

The bone core can be rolled gently before fixing in formalin, providing cytology specimens in addition to the histologic sections  
Step 2 - Close skin

• Close wound using single skin suture .

Aftercare

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• Broad spectrum antibiotic cover should be given in animals which are neutropenic.

• Occasionally bleeding/bruising may be significant in animals with severe thrombocytopenia  or in cases with DIC . However, thrombocytopenia is not a contraindication to bone marrow biopsy (it may be the only way of establishing a diagnosis). It may be wise to choose a biopsy site, eg proximal humerus, where hemorrhage is easily controlled with a pressure wrap and muscle masses are avoided.

Sequelae

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• Failure to collect marrow is usually due to poor technique.
• Biopsy from an uninvolved site.

Sources

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• Recent references from PubMed.
• Villiers E J & Dunn J K (1999) Clinicopathological features of seven cases of canine myelofibrosis and the possible relationships between the histological findings and prognosis. Vet Rec 145 (8), 222-228.
• Dunn J K (1992) Bone marrow aspiration and biopsy in small animals - indications and techniques. Vet Ann 32 , 107-118.

• O'Keefe D A (1992) Bone marrow biopsy - indications and techniques. In: Kirk's Current Veterinary Therapy, Volume 6. Ed J D Bonagura. Philadelphia, PA: W B Saunders Co. pp 488-492.

• Dr Kyle Braund BVSc MVSc PhD FRCVS DipACVIM , Veterinary Neurological Consulting Services, 1476 Lakeview Ridge, Dadeville, AL 36853, USA.

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