This article addresses the technique of endoscopic ultrasound–guided fine-needle aspiration of solid lesions to obtain cytologic specimens. The technique can be broken down into a sequence of steps. The ultimate goal is to maximize the likelihood of obtaining adequate tissue for diagnostic purposes. This requires a technique that ensures that the needle can be moved inside the lesion, under ultrasound guidance, as widely as possible, as easily as possible, and safely. The other variables such as suction, needle type, and stylet use are of secondary importance.
Key points
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For solid lesions, the basic endoscopic ultrasound (EUS)-guided fine-needle aspiration (FNA) technique consists of proper positioning and moving of the needle inside the lesion with multiple to and fro movements, under ultrasound guidance.
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Many additions to the basic EUS-FNA technique have been described, but none appear to clearly improve the yield other than moving the needle effectively and in many different areas of the lesion.
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For the goal of obtaining cytologic specimens, there is no clear advantage to use of the stylet, suction, larger diameter needles, or other modified needles.
Introduction
For the purposes of this article, the authors assume that the goal of solid lesion endoscopic ultrasound (EUS)-guided fine-needle aspiration (FNA) is to obtain material for cytologic smears and/or for a tissue cell block (which can be processed to permit histologic analysis). EUS-guided FNA biopsy (FNAB) differs from FNA in that FNAB refers to sampling techniques designed to obtain a “ core” specimen for pure histologic analysis. This article will not address puncture of cystic lesions.
The authors describe a basic EUS-FNA technique that they believe should be used at all times, but that can be modified by changing other variables such as suction or different needle types and sizes.
Introduction
For the purposes of this article, the authors assume that the goal of solid lesion endoscopic ultrasound (EUS)-guided fine-needle aspiration (FNA) is to obtain material for cytologic smears and/or for a tissue cell block (which can be processed to permit histologic analysis). EUS-guided FNA biopsy (FNAB) differs from FNA in that FNAB refers to sampling techniques designed to obtain a “ core” specimen for pure histologic analysis. This article will not address puncture of cystic lesions.
The authors describe a basic EUS-FNA technique that they believe should be used at all times, but that can be modified by changing other variables such as suction or different needle types and sizes.
Cytology: advantages, limitations
These issues are beyond the scope of this article and will be addressed by others. Suffice it to say that, in the authors’ experience, standard cytology, combined with a cell block (when special stains are required) is largely sufficient to obtain a diagnosis in more than 95% of cases in a standard EUS practice. A true histologic “core” is needed only in cases where tissue structure is important (eg, suspected lymphoma) or in cases where cytologic specimens are often poorly cellular (eg, suspected linitis plastica, leiomyoma, etc.).
Indications/contraindications
Indications for EUS-FNA for tissue acquisition have broadened over time. Tissue sampling is performed most often to confirm suspected cancer, although it may also be useful in benign conditions such as diagnosing sarcoidosis or infections (eg, tuberculosis, fungal disease, etc.). Box 1 summarizes the common sites for performing EUS-FNA.
Pancreas
Bile duct
Digestive wall lesions a
Suspicious wall thickening
Subepithelial lesions
Adrenal glands
Liver
Retroperitoneal masses
Lymph nodes
Posterior mediastinum
Suspicious lymph nodes
Pulmonary masses b
a Digestive wall lesions include the esophagus, stomach, duodenum, and rectum.
b Pulmonary masses must abut the posterior mediastinum to be vizualized under EUS.
Contraindications to EUS-FNA are few. Before performing EUS-FNA, the endosonographer must be certain that there is a reasonable chance that tissue sampling will be clinically useful.
As a general rule, FNA should be avoided in patients with significant coagulopathy (INR>1.2, platelets <100,000, recent use of thienopyridines [eg, clopidogrel], etc.). However, the use of aspirin or nonsteroidal antiinflammatory drugs (NSAIDs) is not a problem. Patients receiving anticoagulant therapy such as warfarin or dabigatran should discontinue their medication before the procedure (3–5 days for warfarin, 48 hours for dabigatran). If the patient is at high risk for thromboembolic events, bridge therapy with low molecular weight heparin should be considered. Patients receiving antiplatelet therapy such as (eg, clopidogrel) should also withhold them for 7 to 10 days before the procedure if they carry a low thromboembolic risk.
Some high-risk patients may not safely discontinue their treatment. In these situations, where the risk of stopping anticoagulation is potentially greater than the risk of FNA-induced bleeding (eg, FNA of a large mediastinal node in a patient anticoagulated for massive pulmonary embolus), it may be reasonable to attempt EUS-FNA without stopping anticoagulants, while using a small gauge (25g) needle and minimizing the number of passes (eg, with onsite cytology).
Finally, certain anatomic challenges may also contraindicate EUS-FNA, such as a large vessel or duct interposing itself between the targeted lesion and the ultrasound probe. Lymph nodes may not be accessible if the primary mass is preventing direct node sampling, carrying the risk of false-positive results. Box 2 provides an overview to EUS-FNA contraindications.
Contraindication for endoscopic examination
Cardiac or respiratory instability
Suspected perforated viscus
Nonfasting patient or undecompressed upper gastrointestinal obstruction
Coagulation disorder
Anticoagulants
Antiplatelet therapy a
Inaccessible lesion
Lesion not visualized
Large vessel or duct interposition
Metastatic lesion with primary mass interposition
EUS-FNA results will not alter subsequent management
a Aspirin or nonsteroidal antiinflammatory drug use is not contraindicated.
The basic EUS-FNA technique
For didactic purposes, the basic EUS-FNA technique has been broken down into multiple components. In reality, the process should be a smooth, seamless process.
Identify and Characterize the Lesion
Obviously, the lesion must be identifiable before FNA can be attempted. However, the initial assessment should also try to characterize the lesion as solid or cystic because the indications and risks of puncture of cystic lesions are not the same as for solid lesions. The technique of EUS-FNA for cystic lesions is beyond the scope of this article.
Assess the Indication and Rule out Contraindications for EUS-FNA
Not all solid lesions should undergo FNA. FNA should be performed only if the benefits outweigh the risks. Since the risks of solid lesion EUS-FNA are generally small, it is probably reasonable to perform EUS-FNA in most indeterminate solid lesions, but there are notable exceptions. If there is any doubt, this issue should be addressed with the referring physician before the procedure (or even during the procedure), if necessary.
EUS-FNA should be avoided if it clearly does not influence management or treatment, if there is a risk of tumor seeding that could worsen clinical outcomes, if there is an excessive risk of puncture-related complications (eg, bleeding, infection, trauma to surrounding structures, hypertensive crisis [eg, possible pheochromocytoma]).
When faced with the possibility of performing FNA on multiple sites, one should focus on the lesion likely to provide the most relevant information first. For instance, in the setting of a pancreatic head mass with suspicious liver nodules, FNA of the liver lesions may provide a positive cytologic diagnosis and confirm that the patient is not a surgical candidate.
Position the Echoendoscope (as Straight as Possible)
Whenever possible, the echoendoscope should be straight. This makes needle movement easier and reduces the risks of damage to the accessory channel during insertion of the needle into the scope.
In our experience, most pancreatic lesions (including pancreatic head/uncinate lesion) can also be biopsied with the scope in a straight position. To do so, the scope should be passed into the second duodenum and then withdrawn into a “short” position. By withdrawing the scope toward the duodenal bulb, most pancreatic head lesions can be accessed and punctured. However, when withdrawn sufficiently, this position will become unstable, and the scope will slip into the stomach. Lesions near the pancreatic genu are often difficult to biopsy with this withdrawal technique because they often become visible just at the moment that the position becomes unstable.
For these lesions (and any other lesions that cannot be accessed with the scope in a straight position), it is necessary to assume a “long” position, with the scope in the bulb or prepyloric region. This position will also provide a mechanical advantage when trying to puncture indurated lesions in the pancreatic head region.
Select the Appropriate Needle
The 22g needle was used initially for EUS-FNA, but later 19g and then 25g needles became available. More recently, needles with a distal notch have gained favor for some authors.
There is growing consensus that the smaller needles, especially the 25g needle, are easier to use, produce less bloody samples, and increase the yield for malignancy.
Newer notched needles claim to more easily provide core samples and to improve the yield of cytologic specimens. Currently, the data are conflicting, and more randomized trials comparing these needles to standard needles are required.
For cytology, the authors use exclusively the 25g needle for all solid lesion EUS-FNA.
Insert the Needle into the Scope
If at all possible, the needle should be inserted into the scope with the scope in a straight position. Therefore, even if the lesion can only be accessed with the scope in a long position, it is best to withdraw the scope into a straight position, insert the needle, and then to reposition the scope for biopsy. One should never use excessive force to push the sheath past an excessive bend, as this could result in perforation of the inner lining of the biopsy channel. Instead, the echoendoscope should be withdrawn into a straight configuration before attempting to reinsert the needle system completely.
For lesions to be accessed from the second duodenum, the needle should be inserted into the scope only after the scope has been placed into the second duodenum. In other words, the duodenal sweep should not be negotiated with the needle and/or sheath protruding from the biopsy channel because there is a risk if duodenal laceration during this maneuver.
The rubber cap covering the operating channel must be removed before inserting the needle system. Once the needle is fully inserted into the echoendoscope, the base of the needle should be luer-locked to the operating channel ( Fig. 1 ).
Related posts:
New Methods to Obtain Better Tissue Samples with EUS-guided FNA
Preface: EUS-Guided Tissue Acquisition
The Changing Paradigm in EUS-Guided Tissue Acquisition
Endoscopic Ultrasound-Guided Fine-Needle Aspiration Needles
Techniques for Endoscopic Ultrasound-Guided Fine-Needle Biopsy
Tips to Overcome Technical Challenges in EUS-guided Tissue Acquisition
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