How to Perform Endoscopic Ultrasonography-Guided Fine-Needle Aspiration

Key Points

•

The needle should be kept in the visual plane at all times.
•

Excessive force should never be used to pass the needle sheath past an acute bend in the endoscope tip.
•

Use of the stylet does not increase the yield of endoscopic ultrasonography-fine-needle aspiration and is more cumbersome to use.
•

Twenty-five-gauge needles provide better diagnostic yield when sampling pancreatic lesions compared with 22-G needles.
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When aspirating a cyst, the endosonographer should fully aspirate all fluid, make only one pass, use antibiotics, and not try to perform aspiration cytology from the cyst wall.

Introduction

Fine-needle aspiration (FNA) provides some of the most clinically powerful information that endoscopic ultrasonography (EUS) has to offer—pathological confirmation of the presence (or absence) of malignancy and/or metastasis to secondary sites (“histological staging”). Like any procedure, proficiency requires adequate experience, but EUS FNA is not a universally difficult technique to master. Some cases are more technically demanding than others. Sampling a 5-mm pancreatic nodule buried deep in the uncinate process is certainly more challenging than sampling a 4-cm subcarinal lymph node. Interestingly, some of the easiest cases provide information that can have a tremendous impact on patient management (e.g., such as prevention of surgery by documentation of mediastinal node involvement in a patient with non–small cell lung cancer).

EUS FNA can be broken down into a series of steps. Proper execution of each step will make EUS FNA easier and probably increase the yield for malignancy. Experts have varying opinions of the best way to perform EUS FNA; however, objective data are constantly emerging to help clarify which procedural variables improve results and which have no clear impact.

This chapter will provide a detailed description of a generic EUS FNA technique that can be applied to the great majority of lesions, to obtain specimens for cytologic analysis and/or to prepare a cell block. Special consideration will also be given to issues that provide particular challenges.

Cytologic specimens are adequate for diagnostic purposes in the great majority of cases. They can be used to confirm or exclude epithelial malignancies, allow for immunochemical staining (e.g., to diagnose neuroendocrine tumors and small cell lung cancer, to look for specific tumor receptors), and permit flow cytometry, which can help diagnose or exclude monoclonal lymphoid processes. Cytologic specimens may also be sufficient to identify granulomas, which may help diagnose diseases such as sarcoidosis. However, in some cases, true histologic specimens may be required, and core specimens should be sought using larger gauge or specialized needles. The techniques required to obtain a “core” biopsy specimen for true histologic analysis are addressed elsewhere.

Indications and 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 (e.g., tuberculosis, fungal disease). Table 20.1 summarizes the common sites for performing EUS FNA.

TABLE 20.1

Common Sites for Performing Endoscopic Ultrasonography-Fine-Needle Aspiration

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 visualized under endoscopic ultrasonography.

Contraindications to EUS FNA are limited. 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 (international normalized ratio [INR] >1.5, platelets <100,000, recent use of thienopyridines [e.g., clopidogrel], etc.). However, the use of aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) is not a problem. Patients receiving anticoagulant therapy such as warfarin or novel oral anticoagulants (NOACs) such as dabigatran should discontinue their medication prior to the procedure (3 to 5 days for warfarin, 48 hours for NOACs). 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 clopidogrel should also withhold them for 7 to 10 days prior to 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 (e.g., 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 (25-G) needle and minimizing the number of passes (e.g., with onsite cytology).

Finally, certain anatomical 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. Table 20.2 provides an overview to EUS FNA contraindications.

TABLE 20.2

Contraindications for Performing Endoscopic Ultrasonography-Fine-Needle Aspiration

Contraindication for endoscopic examination
- Cardiac or respiratory instability
- Suspected perforated viscus
- Nonfasting patient or undecompressed upper GI 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

EUS FNA, Endoscopic ultrasonography-fine-needle aspiration; GI, gastrointestinal.

a Aspirin or nonsteroidal anti-inflammatory drug use are not contraindicated.

Steps for Endoscopic Ultrasonography-Fine-Needle Aspiration

1.

Verify the indication.
2.

Localize the lesion and position the echoendoscope.
3.

Choose the correct needle.
4.

Insert the EUS FNA needle into the echoendoscope.
5.

Position the lesion in the needle path.
6.

Puncture the lesion and move the needle within the lesion.
7.

Withdraw the needle and process the aspirate.
8.

Prepare the needle for subsequent passes.
9.

Evolving trends in EUS FNA:
- a.
  
  Use of the stylet
- b.
  
  Use of suction
- c.
  
  Sampling techniques
10.

FNA particularities according to site:
- a.
  
  Esophagus
- b.
  
  Stomach
- c.
  
  Duodenal bulb
- d.
  
  Duodenal sweep (D2)

Verify the Indication

Before performing EUS FNA, the indication should be clear and the endoscopy suite and team adequately prepared. Like any test, EUS FNA does not need to “change management” to be useful. However, before considering EUS FNA in a given patient, it should be clear that the information obtained has a reasonable chance of being clinically useful (to those managing the patient and/or to the patient). If the endosonographer is not in charge of the patient’s management, his or her opinion as to the value of the information need not affect the decision to perform EUS FNA, unless there is compelling evidence that the risks of the procedure will likely far outweigh the possible benefits. If there is any doubt, these issues should be addressed with the referring physician before the procedure (or even during the procedure) if necessary.

EUS FNA should be avoided if it will clearly not influence management or treatment, if there is a risk of tumor seeding that could worsen clinical outcomes, or if there is an excessive risk of puncture-related complications (e.g., bleeding, infection, trauma to surrounding structures).

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 cytological diagnosis and confirm that the patient is not a surgical candidate.

Localize the Lesion and Position the Echoendoscope

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 sampled 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 too far, 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.

Choose the Correct Needle

At the time of this writing, there are three needle sizes available for EUS FNA that can be used to obtain material for cytology: 19 G, 22 G, and 25 G. These needle sizes are also available in models featuring a beveled side-hole near the tip, or multiple prongs, which may help collect more material into the needle.

There is increasing evidence that smaller needles offer at least similar results in diagnostic yield compared with larger needles, while at the same time being easier to manipulate. Large-diameter needles tend to be harder to maneuver (particularly the 19-G needle), are more traumatic, and may provide bloodier samples—which may actually reduce their effectiveness when compared with smaller diameter needles. Traditionally, 22-G needles were used for solid lesions, mainly because it was the first size that was commercially available. However, 25-G needles eventually came to market, and some hypothesized that a 25-G needle would be better (easier to penetrate hard lesions and more maneuverable, providing less bloody aspirates)—particularly for challenging pancreatic head lesions.

The first retrospective comparisons of the 22-G and 25-G needles showed the 25-G needle to be more sensitive for cancer in pancreatic masses, but subsequent, prospective studies failed to show statistically significant advantages. However, a recent meta-analysis showed that, for pancreatic masses, the sensitivity of the 22-G needle is clearly inferior to that of the 25-G needle (85% [95% confidence interval (CI): 82 to 88%] vs. 93% [95% CI: 91% to 96%], P = .0003). Given that the 25-G needle is more flexible, and hence easier to manipulate, it appears reasonable to favor the 25-G needle for all cases of solid lesion EUS-guided FNA when the objective is to obtain material for cytology. Table 20.3 summarizes the available data from randomized trials comparing needle sizes.

TABLE 20.3

Randomized Trials Comparing 22 Versus 25 Needle Gauges in Pancreatic and Nonpancreatic Lesions

Author, Year	No. Patients	Lesion	Accuracy % (22 G)	Accuracy % (25 G)
Siddiqui UD, 2009	131	Pancreatic	88	96
Camellini L, 2011	127	All	78	78
Fabbri C, 2011	50	Pancreatic	86	94
Lee JK, 2013	188	Pancreatic	89	88
Vilmann P, 2013	135	All	89	90
Carrara S, 2016	144	All	68	81

Insert the Endoscopic Ultrasonography-Fine-Needle Aspiration Needle Into the Echoendoscope

Whether or not the needle system is inserted into the biopsy channel before or after the echoendoscope is in position for FNA is a matter of personal preference. However, it should be noted that once the echoendoscope is in position, it might be difficult or impossible to pass the needle system completely into position if the echoendoscope is not sufficiently straight. In this situation, the sheath may become stuck in the bending portion of the instrument near the tip. One should never use excessive force to push the sheath past an excessive bend at this location, because the needle sheath may perforate the inner sheath 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 of duodenal laceration during this maneuver. The scope should be positioned in a “short scope” fashion prior to attempting needle insertion.

The rubber cap covering the operating channel must be removed prior to 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. 20.1 ).

In some cases, a lesion that is clearly visible before the needle deployment may become difficult to see once the needle assembly is in place. The needle/sheath may produce artifact or may slightly reduce complete coupling between the ultrasound probe and the gut wall, producing air artifact. Slight repositioning of the echoendoscope, application of suction, or reinsertion of the needle assembly may help correct the problem.

Position the Lesion in the Needle Path

Optimal positioning of the echoendoscope with respect to the lesion should make EUS FNA easier, safer, and more effective. The needle sheath should be adjusted so that it protrudes just beyond the elevator. Most commercially available needles are manufactured with a sheath length adjuster. This device is located near the bottom of the needle shaft and allows the endosonographer to determine the proper length of sheath to exit the echoendoscope into the gut lumen (see Fig. 20.1 ). In order to minimize ultrasound artifacts caused by the shaft and to maximize elevator deflection capabilities, the needle sheath should be kept at a short distance from the operating channel exit. However, to avoid traumatizing the inner lining of the operating channel during needle deployment, one must be certain that the needle sheath terminates outside the operating channel ( Fig. 20.2 ).

After needle sheath adjustment is performed, the screw must be tightly wound to avoid inadvertently advancing the sheath during needle thrusting, which could result in gut wall trauma. Needle sheath adjustment is usually performed when the needle is first used, and rarely requires further manipulation during the subsequent passes.

Once the lesion is identified, it should be positioned as much as possible within the natural path of the needle (i.e., the path taken by the needle when no elevator is applied; Fig. 20.3 ). This varies depending on the instrument used. If this is not possible, it should be positioned within the range of deflection offered by the elevator ( Fig. 20.4 ). The elevator can be used to increase the angle formed between the echoendoscope shaft and the needle. It cannot reduce this angle ( Fig. 20.5 ). Once adequate elevator adjustment is attained, it is best to lock the up-down control, so that the thumb can then be used to move the elevator, if needed.

A stopping device locks the needle inside the sheath, avoiding accidental injury or scope trauma during manipulation and insertion of the needle into the echoendoscope. Prior to puncturing the lesion, the stopping device must be unscrewed to allow needle deployment. The stopping device can be set so as to limit the maximum distance that the needle can travel ( Fig. 20.6 ). This can be helpful in situations where inserting the needle beyond the limits of the target lesion would be dangerous (e.g., the target lies directly over a vascular structure). To ensure maximum control, the fixed component of the needle handle should be grasped between the palm and the last two or three fingers of the right hand. The movable portion should be held between the thumb and index finger. This allows fine or vigorous needle movements to be performed, but with control. Any method that does not allow such control should be avoided ( Fig. 20.7 ).