Ultrasound-guided fine-needle aspirate and biopsy technique Copyright © 2010 The Academy of Veterinary Imaging
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Introduction This presentation describes the methods to use as well as other factors to consider when performing an ultrasound-guided fine-needle aspirate (FNA) or core biopsy. The scanning planes used for FNA and core biopsy are the same. The technique varies somewhat, and the differences are demonstrated. Animation is used to demonstrate the aspirate/biopsy techniques. Please note that this animation will not run properly with older versions of PowerPoint or PowerPoint viewer.
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Ultrasound-guided FNA and biopsy technique Indications Method details: Rock/slide the probe Accuracy Keep needle in plane of beam Probe orientation Animal preparation Screen orientation Superficial lesion Materials Deep lesion Reset (exit) program Method References
Indications There are many indications for ultrasound-guided aspirates and biopsies as there are essentially no pathognomonic lesions in ultrasound. Most of the time a cytologic or histopathologic sample is needed to make a definitive diagnosis. Samples for cytology and histopathology may obtained with ultrasound-guided, laparoscopic and surgical procedures.
Indications Icterus/liver enzyme elevation/elevated bile acids Splenomegaly Focal nodules or masses anywhere Renal disease sometimes (i.e. renal dysplasia, renal masses, lymphosarcoma suspects) Prostatomegaly Free abdominal fluid Cysts Lymphadenopathy U/S guided FNA/biopsies generally not done on: Adrenal glands Transitional cell carcinoma suspect masses Chronic renal failure, glomerulonephritis
Accuracy Currently there is a lack of consensus about the accuracy of ultrasound-guided fine needle aspirates and biopsies compared to surgical or post mortem biopsy sample results. Some studies report high accuracy, others, low accuracy. The differential diagnosis and case presentation both should be considered when determining the best method of obtaining a cytology or histopathology sample.
Animal preparation Coagulation concerns: A physical examination should be done to assess evidence of a coagulopathy, and if one is suspected, no aspirate or biopsy is recommended. The pre-biopsy hematocrit should be known. At least a platelet count is recommended before a fine-needle aspirate is done. Perform a buccal mucosal bleeding time if i.e. von Willebrand’s disease, or other disorders of primary coagulation are suspected. A platelet count as well as coagulation profile (PT, aPTT and/or PIVKA) are recommended before a core biopsy is done. Sedation/brief anesthesia may be indicated. Prepare a sterile field
Coagulation tests PT = Prothrombin time PTT = Partial thromboplastin time PIVKA = Proteins induced by vitamin K antagonism
Materials Biopsy guide or not 22-G 1.5 inch “cysto’ needle or 22-G 3.5 inch spinal needle is often used for fine-needle aspirates. Attach needle to extension set then syringe for easier handling 14-G to 18-G core biopsy needles Bard® automatic biopsy needles One hand to trigger Forward ‘throw” varies from 11 to 22 mm Order from Sound Technologies or other distributors
Method Biopsy guide or freehand Thickness of beam is 1-2 mm Must keep needle in plane of beam (biopsy guide would do this for you) Shortest distance/safest pathway “Sewing-machine” motion for fine-needle ‘aspirates’ Stab incision in skin before doing a core biopsy Sample preparation and evaluation: Spray aspirates carefully on the slide Smear gently, dry rapidly View representative slide before submitting Place core biopsy samples in cassette, pouch or lens paper Pick pathologist carefully
Probe orientation Reference marker corresponds to left side of screen (see Screen Orientation slide) Probe Skin Schematic of the resulting ultrasound image Superficial “lesion” to biopsy Deep “lesion” to biopsy
Screen orientation Near field Opposite reference marker Far field
Rock and/or slide the probe to a “reachable” position to line up the lesion to a “reachable” position Superficial lesion can be toward the edge or in the center of the beam Deep lesion needs to be lined up toward the edge of the beam
Keep needle in the same plane as the beam See rotated views
Keep needle in the same plane as the beam: Rotated views of the probe/beam/biopsy plane Needle is placed in the plane of the beam
Angle to use for a superficial lesion: Aim needle more perpendicular to beam FNA: Core biopsy:
Superficial lesion FNA
Superficial lesion FNA
Superficial lesion FNA
Superficial lesion FNA
Superficial lesion FNA
Superficial lesion FNA
Superficial lesion FNA
Superficial lesion FNA
Superficial lesion FNA
Superficial lesion core biopsy
Superficial lesion core biopsy Take biopsy
Superficial lesion core biopsy
Superficial lesion core biopsy
Superficial lesion core biopsy
Superficial lesion core biopsy Take biopsy
Superficial lesion core biopsy
Superficial lesion core biopsy
Superficial lesion core biopsy
Superficial lesion core biopsy Take biopsy
Superficial lesion core biopsy
Superficial lesion core biopsy
Angle to use for a deep lesion: Aim needle more parallel to beam FNA: Core biopsy:
Deep lesion FNA
Deep lesion FNA
Deep lesion FNA
Deep lesion FNA
Deep lesion FNA
Deep lesion FNA
Deep lesion FNA
Deep lesion FNA
Deep lesion FNA
Deep lesion core biopsy
Deep lesion core biopsy Take biopsy
Deep lesion core biopsy
Deep lesion core biopsy
Deep lesion core biopsy
Deep lesion core biopsy
Deep lesion core biopsy Take biopsy
Deep lesion core biopsy
Deep lesion core biopsy
Deep lesion core biopsy
Deep lesion core biopsy
Deep lesion core biopsy Take biopsy
Deep lesion core biopsy
Deep lesion core biopsy
Deep lesion core biopsy
References Fife WD (2005) Abdominal ultrasound: Aspirations and biopsies, In Ettinger SJ, Feldman EC (eds), Textbook of Veterinary Internal Medicine, 6th edition, St. Louis, Elsevier Saunders, pp. 271-275. Nyland TG, Mattoon JS, Herrgesell EJ, Wisner ER (2002) Ultrasound-guided biopsy, In Nyland TG, Mattoon JS (eds), Small Animal Diagnostic Ultrasound, Philadelphia, WB Saunders, Co., pp. 30-48.