PHOTOS 1-2: The bone marrow biopsy needle is used to perform biopsies of bone marrow but not the bone. It has a large handle facilitating introduction of the needle into bone and a stylet to prevent tissue coring. PHOTOS 3-4: Bone marrow aspiration biopsy provides information on the condition and activity of the haemopoietic cells in bone marrow. Bone marrow aspiration biopsy is indicated in cases where there is obvious or suggested dysfunctioning of the haemopoietic system but there is insufficient change in peripheral blood to make a diagnosis. Conditions where a bone marrow evaluation is necessary include non regenerative anaemia, pancytopenia, neutropenia, thrombocytopenia, proliferative abnormalities, suspected malignancies and cell maturation problems. Bone marrow aspiration can be done with only light restraint and local anaesthetic. Bone marrow aspiration is a relatively safe procedure with very few contraindications. Bone marrow samples are used for the study of cell markers, cytogenetic study, ultrastructural examination, culture for microorganisms and to culture haemopoietic precursors for the preparation of histological sections. Bone marrow aspirates are the best samples for cytological examination. Bone marrow aspiration is especially useful for investigating suspected aplastic or hypoplastic anaemia, lymphoma, metastatic carcinoma and diseases of bone. The sites that are most commonly used for bone marrow aspiration in small animals are the head of the humerus and the wing of the ilium. It can be done with only light restraint and local anaesthetics. The skin directly over the selected site is clipped and cleaned with a surgical scrub. The area is anaesthetized using a local anaesthetic. An incision just large enough for the bone marrow aspiration needle to pass through is made. The needle is inserted and rotated into the bone. When the needle feels firmly inserted into the bone, the stylet is withdrawn and a plastic syringe is attached to the needle hub. Negative pressure is applied until a few drops of red bone marrow appear in the tip of the syringe. The syringe is removed and the stylet replaced, the needle is then repositioned for another aspiration attempt. The needle is withdrawn from the patient. Cytology smears are made right away to avoid clotting, the slides can be air dried and stained with any Romanowsky stain. Bone marrow samples can also be obtained via open biopsy under general anaesthetic. Complications of bone marrow aspiration are rare but cardiac and great vessel laceration may occur. Haemorrhage is uncommon but prolonged firm pressure may be necessary after the procedure to ensure bleeding stops in patients with bleeding disorders. Biopsy needles may break in patients that have osteosclerosis.
REFERENCES: PHOTOS 1-4: 1. Bain, BJ, Clark, DM, Lampert, IA & Wilkins, BS 2001, ‘Bone marrow pathology’, 3rd ed., Blackwell Science, Malden, MA, pp. 5-7. 2. Lewis, HB & Rebar, AH 1979, ‘Bone marrow evaluation in veterinary practice’, Ralston Purina, St. Louis, pp.1-2. 3. Morrison, WB 2001, ‘Cancer in dogs and cats : medical and surgical management’, 2nd ed., Teton New Media, Jackson, Wyo, pp. 71-77, 118-121. 4. Sonsthagen, TF 2006, ‘Veterinary instruments and equipment : a pocket guide’, Elsevier Mosby, St. Louis, pp.40-41.
Metadata assigned by Dr. M. van Schoor, Senior Lecturer, Dept. of Companion Animal Clinical Studies