Fine-Needle Aspiration of the Liver
Fine-Needle Aspiration
Liver cytology via fine-needle aspiration (FNA) has been shown effective in diagnosing some liver disorders; however, cytologic examination of the liver does have limitations and must be interpreted within the context of the clinical picture.1-5
FNA is a relatively low-risk procedure that usually can be performed without sedation or general anesthesia. Contraindications for liver FNA include coagulopathies, lack of a safe access route (eg, vascular structure in the biopsy path), inexperience on the part of the sonographer, and an uncooperative patient.
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What You Will Need
25-or 22-gauge, 1.5-inch needles
6-mL syringe
Microscope slides labeled with patient name and tissue source
Usually, 25-gauge needles are a good choice with regard to sample size, minimizing hemodilution, and decreasing patient discomfort. Because some lesions do not exfoliate well, a larger-gauge needle can be used.
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A syringe filled with room air is used to blow the sample onto the microscope slide.
Step 1
Prepare the area. If the patient is not already clipped, clip and clean the sampling area; consider a surgical scrub if the skin is particularly dirty or a sample will be submitted for culture. Remove ultrasound gel applied to the area, as it can create an artifact on the slide to be viewed by the pathologist.
Leave the area wet with alcohol or liquid (not jelly) lidocaine as a contact medium for the ultrasound transducer. Clean the transducer by placing an alcohol gauze sponge on the transducer tip while preparing the patient.
Step 2
Locate the sampling area. If a general liver sample is needed, the most accessible portion of the liver should be selected. For diffuse liver disease, target the peripheral aspects of the liver lobes (left of midline) to avoid larger blood vessels that are more central within the hepatic parenchyma and the gallbladder, which is located right of midline.
If culture study of a specific nodule or region of the liver is desired, optimize the image of the region on the ultrasound machine. Take care to locate and avoid any structure in the path of the lesion or in the direct vicinity of the lesion that, if inadvertently sampled, could contribute to complications.
Author Insight: Extreme caution should be made to avoid contact between the transducer and the needle. A distance at least 1 cm should always be kept. The matching layer of the transducer is a soft material and can be easily damaged with a needle. Contact may also increase contamination.
Dan VanderHart, DVM, DACVR, is a clinical instructor for the Department of Small Animal Clinical Sciences at University of Florida. His research interests are specific ultrasonographic characteristics of different tissue types and computed tomographic patterns of hepatic neoplasia. Dr. VanderHart completed his internship at the University of Georgia and his residency at the University of Florida.
Clifford R. Berry, DVM, DACVR, is a professor of radiology for the department of small animal clinical sciences at University of Florida. His research interests are clinical studies in diagnostic imaging, particularly related to the thorax, use of animal models for human disease, use of imaging techniques for the prognosticating disease response in a population of affected patients, and the evaluation of novel approaches for the advancement of diagnostic imaging in clinical and research settings with veterinary and human applications. Dr. Berry completed his residency in diagnostic imaging at University of California, Davis.