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1112 Fine-Needle Aspiration, Ultrasound-Guided

Fine-Needle Aspiration, Ultrasound-Guided
VetBooks.ir Difficulty level: ♦♦ • Do not move the needle side to side within • Ensure that the area of interest is within the

focal zone of the transducer.
an organ because this can cause tissue trauma.
Synonym • If redirecting needle orientation, withdraw • Prepare skin with surgical scrub.
Needle aspiration, fine-needle aspiration (FNA) needle tip to subcutis and then reinsert. • Obtain ultrasound image of area to be
Redirecting with needle fully advanced is sampled.
Overview and Goal ineffective (position changes little or not at • Ensure probe marker location on screen
Procedure to obtain small tissue or fluid samples all) and dangerous (shearing of tissue with corresponds with desired needle course.
using ultrasound guidance and real-time needle tip).
monitoring of needle placement • Avoid penetrating bowel lumen due to risk
of peritonitis.
Indications • Sample the left aspect of the liver when
• Cytologic evaluation of possible to avoid the gallbladder and hilar
○ Mass or nodule vessels on the right. If the liver is small or
○ Diffuse parenchymal organ abnormalities cranially located, consider an intercostal
○ Diffuse infiltrative disease (e.g., mast cell approach.
disease, lymphoma) screening • For renal aspirates, sample the caudal cortex
• Drainage of cysts, abscesses, or fluid of the kidney to avoid the medulla and hilar
vessels.
Contraindications • In cases of bilateral renal abnormalities, the
• Cavitated mass: risk of hemorrhage left kidney should be sampled because of its
• Bleeding disorder: risk of hemorrhage more caudal location.
• Suspected transitional cell carcinoma (p. • Do not pass through an organ other than
991): possibility of seeding tumor along the one being aspirated.
needle tract • Avoid administering drugs that cause sple-
nomegaly or panting (e.g., phenothiazines,
Equipment, Anesthesia some opiates).
• 22- or 25-gauge standard sterile injection • If aspirating an adrenal gland mass, be aware
needles, 1 2 inches (4 cm) in length: of possible blood pressure alterations and
1
• 6-mL syringes severe hemorrhage with pheochromocytoma
• Glass microscope slides (p. 785).
• Hair clippers • Ensure contact between the lesion and
• Surgical scrub, rubbing alcohol chest wall when sampling a thoracic lesion
• Sector or linear-array ultrasound transducer to minimize risk of pneumothorax.
○ Sector transducers allow sampling of deep
structures. Procedure FINE-NEEDLE ASPIRATION, ULTRASOUND-
○ Linear-array transducers provide better • Restrain the animal in dorsal or lateral GUIDED Importance of correct alignment between
resolution of superficial structures. recumbency. A padded U- or V-shaped needle and ultrasound probe. Left, Correct alignment
• Often done with manual restraint alone. trough can be used to make the animal is present, and full extent of needle is seen. Right,
Sedation or even anesthesia sometimes more comfortable. Needle is not aligned with ultrasound beam, and only
required (e.g., anxious animal, small structure • Clip hair at planned needle insertion site. proximal portion of needle is seen. Trauma to deeper
tissues is possible because location of the needle tip
in close proximity to large vessel) • Thoroughly evaluate area of interest, charac- is unknown. (Reprinted from Fife WD: Abdominal
terize lesion by ultrasound, identify vessels to ultrasound: aspirations and biopsies. In Ettinger SJ,
Anticipated Time be avoided, and determine shortest distance et al, editors: Textbook of veterinary internal medicine,
5-10 minutes and safest direction of needle placement. ed 7, St. Louis, 2010, Saunders, pp 376-379.)
Preparation: Important
Checkpoints
• If at increased risk for bleeding, perform
platelet count ± coagulation profile.
• Determine if sedation is required; place
intravenous (IV) catheter if needed.
• Ensure proper animal restraint.
Possible Complications and
Common Errors to Avoid
• To decrease hemodilution, avoid the suction
method in sampling vascular organs (e.g.,
spleen).
• Identify and avoid large vessels.
• Hemorrhage is uncommon if 22- or 25-gauge
needle is used and the movement of the
needle through the entire procedure is FINE-NEEDLE ASPIRATION, ULTRASOUND-GUIDED Views as seen on monitor of ultrasound machine,
one-dimensional (in and out only, with no perpendicular to other figure. Left, Correct alignment produces complete visualization of needle. Right, Probe/
side-to-side motion). needle malalignment underrepresents depth of needle.

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