"Bone Marrow Aspiration" TUMOR TIDBITS, A BIWEEKLY VETERINARY ONCOLOGY E-LETTER Volume 3; Number 13; April 12, 2002. Editor: Kevin A. Hahn, DVM, PhD, Dipl - ACVIM (Oncology) & Overall Nice Guy! www.gcvs.com ====================================================== THIS WEEK'S TUMOR TIDBIT: BONE MARROW ASPIRATION • Bone marrow aspiration and biopsy are essential procedures for determining cytologic and histologic abnormalities of the bone marrow that are caused by a wide variety of neoplastic, infectious, and myelodysplastic conditions. A bone marrow aspirate and biopsy are indicated when an abnormality in blood cell production is suspected or to appropriately stage an animal with a hematopoietic malignancy. • Bone marrow aspiration is performed to acquire a monolayer of cells for individual evaluation. To identify a wide variety of malignant and non-malignant disorders, Romanovsky (including Wright and Giemsa) stains are preferred. When the cytologic diagnosis of a cell type is not certain, additional special stains can be used including myeloperoxidase, Sudan black, and periodic acid Schiff. Bone marrow biopsies are beneficial for determining bone marrow cellularity, the presence and extent of fibrosis or granulomatous conditions, and the presence of non-hematopoietic malignancies. TECHNIQUE • The hair is clipped and the bone marrow aspiration site is prepared with a surgical scrub. Preferred sites and patient positioning include:-dorsocranial or lateral aspects of iliac crest (patient is sternal); greater trochanter of the femur (patient is in lateral recumbency); greater tubercle of the proximal aspect of the head of the humerus (patient is in lateral recumbency) • Using a 25 gauge needle, approximately 2 to 3 mls of the local anesthetic agent, lidocaine, are injected in and around the site where the bone marrow needle is to be introduced. Care is taken to deposit lidocaine in and around all of the tissues that extend from the skin to the bone. • The biopsy area is scrubbed a final time after the lidocaine is injected. A surgical drape can be applied for sterility. • The bone marrow site is identified, the skin is stretched between the thumb and index finger, and a small stab incision is made with a number 11 surgical blade in the area blocked with lidocaine. • The bone marrow needle with the stylette in place is advanced through the stab incision in the skin, subcutaneous tissue, and muscle down to the bone. It is crucial to keep the stylette in place because it has a tendency to back out during the procedure. A 1 to 1.5 inch long, 16 gauge Illinois or Rosenthal bone marrow needle is preferred for dogs, and a 1 inch long, 18 gauge Illinois or Rosenthal needle is preferred for the cat. After a sample is obtained for cytologic evaluation, if a biopsy is required, a Jamshidi needle is utilized. • With the stylette is place, the bone marrow needle is advanced into the bone using a corkscrew motion. The instrument should not be allowed to wobble and the instrument should be fixed firmly into bone like a nail that has been securely hammered into wood. When the needle is firmly fixed in the bone, the stylette is removed and the syringe is affixed. Many clinical pathologists suggest rinsing the syringe and bone marrow needle with EDTA before the procedure to reduce clotting of the bone marrow sample. • The bone marrow sample is then aspirated briskly into the 12 ml syringe; usually 1 ml is adequate. The aspiration may be accompanied with a few seconds of pain, but this cannot be prevented. • If a sample is not obtained, the stylette is replaced in the bone marrow needle and the instrument is then advanced further into the bone for a second attempt at aspirating marrow contents. • Once marrow has been obtained, smears are prepared. • Stain a slide in Diff Quik to be sure you have an adequate sample. Submit stained and unstained slides to your Pathology Laboratory. Consider placing any unused marrow into an EDTA purple top tube and submit that tube along with a freshly collected EDTA whole blood sample so that a concurrent complete blood count can be evaluated. MORE QUESTIONS ABOUT MARROW ASPIRATIONS? Check us out on the web at www.gcvs.com or call us any time (when in doubt, check it out)! ALL THE BEST, Kevin A. Hahn, DVM, PhD Diplomate ACVIM (Oncology) & Overall Nice Guy Gulf Coast Veterinary Diagnostic Imaging & Oncology 1111 West Loop South, Suite 150, Houston, TX 77027 P: 713.693.1166 F: 713.693.1167 http://www.gcvs.com mailto:drhahn@gulfcoastvetspec.com