Thoracentesis, Pleural Biopsy, and Thoracic Ultrasound

General description of procedure, equipment, technique

Thoracentesis is a percutaneous procedure in which a needle or catheter is passed into the pleural space for evacuation of pleural fluid. Most pleural effusions with a depth of greater than 1 cm (as determined by lateral decubitus chest radiography or ultrasound) may be safely tapped using a small-gauge needle. Greater availability of portable ultrasound equipment for procedure guidance has generated improved needle insertion site selection, better characterization of pleural anatomy, and higher rates of procedural success than physical examination alone.

Images reconstructed from CT scan data demonstrate that avoidance of the intercostal artery during thoracentesis is best accomplished by selecting a needle insertion site 10 cm or more lateral to the spine (thereby approximating the posterior axillary line) and following the traditional teaching of “marching” the needle over the superior edge of the lower rib, demarcating the interspace.

Therapeutic thoracentesis is performed to palliate dyspnea or impaired ventilation arising from accumulation of pleural fluid, to improve post-drainage chest imaging, to predict success of lung re-expansion in malignant effusions, or to expedite effusion clearance with a single pleural procedure while awaiting the effect of disease-modulating therapies. These procedures confer an increased risk of pneumothorax, usually as a consequence of an underlying unexpandable lung, which may be predicted by use of pleural manometry. Application of pleural manometry may also minimize the risk of re-expansion pulmonary edema. Post-procedure imaging may be reserved for those with complicated procedures or for patients who develop symptoms or signs of pneumothorax.

Indications and patient selection

The principal indication for diagnostic thoracentesis is the new finding of a pleural effusion. Pleural fluid sampling permits the nature of the fluid to be determined and potential causes to be identified.

In some circumstances, pleural fluid sampling may not be warranted, such as when there is a small pleural fluid volume with a secure clinical diagnosis, as in viral pleurisy, or the presence of congestive heart failure with symmetric bilateral effusions. In the setting of congestive heart failure, sampling pleural effusions should be considered when clinical circumstances include the presence of fever, pleurisy, asymmetric effusion size, greater than expected alveolar-arterial oxygen gradient, or findings that do not clearly substantiate congestive heart failure (e.g., normal echocardiogram, normal brain natriuretic peptide [BNP], no resolution with heart failure therapy).

Contraindications

There are no absolute contraindications to thoracentesis. Relative contraindications to performing thoracentesis include:

Active skin infection at the site of needle insertion. Passage of the needle through infected tissue may seed microbes into the pleural space.
Coagulopathy, bleeding diathesis (including those that are due to renal failure), anticoagulation
Thrombocytopenia
A small volume of pleural fluid, defined as either less than 1 cm thickness on a decubitus chest radiograph, or less than 1 cm thickness in the shortest dimension using two-dimension ultrasound. Although very small effusions can be sampled, risks are likely to increase, and few interventions are warranted with minimal pleural disease.

The safety of thoracentesis in patients with coagulopathy, bleeding diathesis, anticoagulation, or thrombocytopenia has been debated, given a modicum of evidence to guide safety. Most commonly cited is a retrospective review of sequential hemoglobin values in a cohort of patients who underwent a total of 608 thoracenteses and paracenteses (including 217 thoracenteses) without receiving plasma or platelet transfusions (PUBMED:1996485). Bleeding events, defined as a drop in hemoglobin greater than 2 g/dL, were rare (3%, 19/608), and transfusions were administered in only 2 percent. No difference was detected when comparing patients with normal versus mildly or moderately prolonged PTs and PTTs or relative thrombocytopenia. In this cohort, patients with markedly elevated serum creatinine (>6 mg/dL) had a significantly greater average hemoglobin loss. Another retrospective case series that described 1,076 ultrasound-guided thoracenteses demonstrated zero hemorrhagic complications (although limited in the scope of follow-up). In the subset of patients who had pre-procedure measurements, the INR exceeded 2.0 in 17 percent, and the platelet count was less than 50,000/UL in 6 percent (PUBMED:21700980). A more recent study of 312 patients demonstrated no increased risk of bleeding in patients undergoing thoracentesis with active coagulopathy, thrombocytopenia or medication-induced bleeding risks (PUBMED:23952852). Similar results were found in a review of 9,320 inpatient thoracenteses (PUBMED:25378543).

Given these findings, most proceduralists are willing to perform thoracentesis using a small-gauge needle or catheter in the context of relative coagulopathy or thrombocytopenia when landmarks are easily identified (especially a palpable rib edge).

Caution is warranted in performing thoracentesis in patients on mechanical ventilation. Although studies have demonstrated that mechanically ventilated patients who undergo the procedure are not at increased risk for developing pneumothorax, should one occur, the consequences of developing tension physiology or persistent air leak (resulting from bronchopleural fistula) are serious.

Details of how the procedure is performed

Following a standardized approach in performing either diagnostic or therapeutic thoracenteses helps ensure patient safety and optimal yield.

Proper positioning of the patient is important.

If the patient is alert and cooperative, the patient sits upright with his or her arms extended and resting on a surface (e.g., a bedside table) just below shoulder level. Elevation of the patient’s ipsilateral arm widens the intercostal space and facilitates examination. The patient should sit erect if possible to keep the ribs in a vertical alignment minimizing the risk of a tangential needle passage toward the superior intercostal bundle.

For the debilitated, sedated, or critically ill patient who is tethered to support devices, the head of the bed should be slightly elevated and the patient placed in a lateral recumbent or supine position, with the side of the pleural effusion superior. The ipsilateral arm should be positioned above the head or across the chest, directed toward the opposite side.

Following a "checklist" of steps prior to the procedure facilitates consistency of approach

Obtain informed consent.
Collect necessary equipment.
Review relevant coagulation and radiology studies to confirm the side of the pleural effusion.
Select site (as below) and mark the site of needle insertion.
Conduct a formal “time out” with the patient and bedside nurse in order to affirm the correct patient, the side of the effusion, and consent for the procedure.

Proper selection of the site for needle insertion is critical

Thoracentesis is one of the few bedside procedures with necessary laterality. Site selection is guided by review of relevant radiology, coupled with physical examination or ultrasound. The puncture site selected must be located in the lateral aspect of an interspace overlying the effusion to mitigate risk for laceration of a tortuous intercostal artery. Ultrasound-assisted thoracentesis is becoming the standard of practice due to the limitations of the physical examination and its ability to visualize complexities of the pleural space (loculations, nodules, etc.).

Location of fluid

When ultrasound is not available to guide needle insertion site in a patient with a non-loculated, free-flowing effusion, the insertion should be 1-2 interspaces below the level at which breath sounds decrease or disappear and the percussion note is dull. The site should be above the ninth rib in order to avoid subdiaphragmatic puncture.

Ultrasound is superior to physical examination in determining fluid location and complexities of local anatomy and in conducting surveillance of pleural space abnormalities (e.g., the presence of loculations, nodules, masses). In experienced hands, ultrasound guidance increases the likelihood of a successful thoracentesis when compared to physical examination (see below). In patients with thick chest walls and non-palpable ribs, ultrasound can localize the rib.

Furthermore, ultrasound may be used to estimate the required depth of needle insertion from chest wall to fluid pocket, the fluid volume, and the size of the drainage window (to prognosticate safety). For procedures with a perceived high risk of pneumothorax, some proceduralists advocate pre-procedure scanning to assess “lung sliding.” This assessment can be compared to a post-procedure assessment to identify pneumothorax. Site localization should be performed with the patient in the same position that he or she will assume during the procedure. The advantages of ultrasound site selection are diminished if ultrasound is used to mark a puncture site and the patient’s position subsequently changes.

Avoidance of intercostal arteries

Elderly patients may have intercostal arteries with a tortuous course, posing an increased risk of arterial puncture even when the needle is carefully passed over the superior margin of the lower rib of the interspace. Three-dimensional reconstructions of contrast-enhanced chest CT scans demonstrate that intercostal arteries do not routinely lie within the intercostal groove in the midline of the posterior thorax. Selection of a more lateral needle insertion site (e.g., one approximately 9-10 cm lateral to the spine or a site that approximates the posterior axillary line) provides the safest route for minimizing injury to an intercostal artery (PUBMED:20154433, PUBMED:20718909).

Choice of equipment is important

Numerous thoracentesis kits are commercially available; they offer highly variable catheter sizes (5 to 8 French) and configurations (e.g., pigtail, straight, with or without fenestrations or side ports). The operator should use a kit with which he or she is familiar.

Procedure steps for diagnostic thoracentesis

(1) Sterilize a wide area surrounding the puncture site with chlorhexidine 0.05% (applied with vigorous scrubbing) or povidone-iodine 10% in circular fashion with adequate drying time.

(2) Affix a sterile drape.

(3) Administer anesthetic (1-2% lidocaine) with a subcutaneous wheal using a 25-gauge needle.

(4) Administer deeper anesthesia using a 21-gauge needle directed at the upper margin of the lower rib and then “walking” over the superior margin of the rib (to minimize risk of injury to the neurovascular bundle). In administering the anesthetic, consider the following:

Anesthetic is injected in increments, assuming no blood or pleural fluid return from aspiration.
When the needle contacts the rib, generous anesthesia should be applied to the rib surface.
Once pleural fluid is aspirated, the needle should be slowly withdrawn to the point of no fluid return, and lidocaine is administered heavily to anesthetize nerve pleural nerve endings/parietal pleural surface. Avoid injection of lidocaine into the pleural space.
Real-time ultrasound guidance permits visualization of the needle tip, pleural surface, and expansion of the anesthetic wheal.

(5) Aspirate as the needle is passed deeper (accomplished with or without real-time ultrasound guidance).

(6) Advance a large-volume syringe (20 or 60 mL) attached to a 21-gauge needle (1.5 inches long) through the anesthetized tract until fluid is aspirated. In performing a diagnostic thoracentesis, note the following:

Some authors advocate addition of 1 mL of 1:1000 heparin to the syringe in order to prevent clotting of hemorrhagic or highly proteinaceous fluid.
Approximately 20-70 mL of fluid should be withdrawn for analysis before removal of the needle.
For suspected malignancy, analysis of a 50 mL sample has greater sensitivity compared with 10 mL sample (PUBMED:19741064). Analysis of volumes above 50 mL does not significantly increase the yield of pleural fluid cytology (PUBMED:19017891). However, more fluid may provide larger cell blocks and more readily permit mutational analysis when necessary.

(7) Prepare samples for analysis.

Procedure steps for therapeutic thoracentesis

Steps 1 – 5 are identical to those for diagnostic thoracentesis.

(6) Attach a 10 mL syringe to the catheter and advance the catheter through the anesthetized tract until fluid is aspirated.

(7) Once fluid is aspirated, stabilize the needle position and deploy the catheter to the skin surface. In performing a therapeutic thoracentesis, note the following:

In order to prevent air entry into the pleural space, catheters without a valve system should be occluded by the operator’s finger following removal of the stylet.
A three-way stopcock can then be attached to the catheter to control aspiration and avoid air entrainment.
Drainage tubing is attached to the stopcock. Drainage can be accomplished manually using a syringe (using a one-way valve) or via a large evacuated container. Use of vacuum bottles has been associated with a higher incidence of pneumothorax (likely secondary to continued drainage, despite significantly negative pleural pressures). (PUBMED:10767236)

Cautionary notes during and following the procedure

In the absence of pleural monitoring (see below), vigilance for vague chest discomfort–a surrogate symptom of dropping pleural pressure–is necessary and should prompt termination of drainage.

Patients with persistent chest pain at the conclusion of drainage, especially those determined to have exceedingly negative pleural pressure (i.e., less than 20cm H₂O), may benefit from purposeful entrainment of air through the catheter during a breath hold at end-expiration. This entrainment can be guided via manometry or brief empiric entrainments of air with periodic reassessment of symptoms. (The former method is more accurate.) These intentional pneumothoraces may be both therapeutic (in relieving pain) and helpful in diagnostics (create air-contrast for CT scanning) in the evaluation of pleural thickening or lobar atelectasis.

Steps at the conclusion of either diagnostic or therapeutic thoracentesis:

Remove the catheter while the patient holds his or her breath at end-expiration; cover the site with an occlusive dressing.
Consider which tests should be performed on the fluid. Commonly performed studies include cell count; pH determination; measurement of protein, lactate dehydrogenase (LDH), glucose, and amylase concentrations; gram stain; culture; and cytology. Samples in which a pH measurement is to be made should be collected directly from the catheter using an arterial blood gas syringe precoated with heparin. The sample should be purged of air bubbles and placed on ice for analysis within one hour. (Air, lidocaine, and heparin may alter fluid pH.)
Diagnostic chest imaging is not indicated for most non-ventilated patients who are asymptomatic. Indications for performing a diagnostic test (chest radiograph or portable ultrasound) to survey for pneumothorax include the aspiration of air during the procedure, development of symptoms or signs of pneumothorax, or a procedure that required multiple needle passes to complete.

Interpretation of results

See the chapter on pleural effusion.

Performance characteristics of the procedure (applies only to diagnostic procedures)

Not applicable.

Outcomes (applies only to therapeutic procedures)

Not applicable.

Alternative and/or additional procedures to consider

Thoracentesis may be deferred in cases of a small volume of pleural fluid, defined as either less than 1 cm thickness on a decubitus chest radiograph, or less than 1 cm thickness in the shortest dimension on a two-dimensional ultrasound image. Although such small effusions can be sampled, the risks increase, and interventions for minimal pleural disease are limited. If the underlying disease or pleural effusion is clinically significant, the effusion will increase in size over time and become amenable to thoracentesis.

During a thoracentesis, the operator would like to remove as much fluid as possible. Complete evacuation of the pleural space may maximize symptomatic relief, spare the patient multiple procedures, increase the yield of post-drainage imaging (especially CT scanning), and provide documentation of lung re-expansion prior to attempts at pleurodesis.

However, re-expansion pulmonary edema (RPE), a well-recognized complication of therapeutic thoracentesis, may arise from rapid lung re-inflation after a period of collapse. Historical recommendations to prevent RPE suggest that pleural fluid removal should not exceed 1.5 liters during a single procedure. Furthermore, evacuation of pleural fluid when there is an unexpandable lung may create significant patient pain, a pressure-dependent, parenchymal-pleural fistula, and drainage-related pneumothorax (pneumothorax ex vacuo).

Pleural pressure monitoring may be performed to document an underlying unexpandable lung (through generation of “pleural elastance curves”) and may minimize the risk of re-expansion pulmonary edema by avoiding excessively negative pleural pressure. However, recent investigations have demonstrated that development of RPE correlates poorly with the volume of fluid removed.

In conducting pleural pressure monitoring: (1) The catheter is inserted at the most dependent portion of the effusion, which is the reference point for a pressure of zero. (2) The catheter is then attached to either a simple water column manometer or an electronic transducer system that is connected to a hemodynamic monitor. Portable ICU monitors with transduction capability are appealing, but they require two adjustments: an offset to compensate for an inability to measure negative pressures, and a correction factor to convert mm Hg to cm H₂O. (3)

End-expiratory pressure is measured initially and at times of removal of each 250 ml aliquot thereafter. If an unexpandable lung is suspected, measurements concurrent with removal of smaller aliqots of 50-100 mL are recommended. The last pressure measurement is valid when residual pleural fluid can be seen on ultrasonography or at least 20 mL more fluid can be withdrawn at the conclusion of the procedure.

In performing procedures guided by pleural manometry, thoracentesis should be terminated if the patient develops chest discomfort or has an end-expiratory pleural pressure less than 20 cm H₂0, or when no more fluid can be removed. Drainage-related pneumothorax may occur despite a paucity of symptoms and avoidance of excessively negative pleural pressures (less than -20cm H₂O) via periodic manometry readings.

Tube thoracostomy is performed for hemothorax, empyema, or complicated parapneumonic effusions.

Patients with recurrent malignant pleural effusion should be evaluated for pleurodesis or insertion of a tunneled pleural catheter.

Pleural biopsies are typically performed for undiagnosed exudative pleural effusions and abnormal pleural thickening (see below).

Complications and their management

Potential complications of thoracentesis, which should be discussed with patients prior to performing the procedure, include:

pain at puncture site
sustained cough
chest pain
pneumothorax
vasovagal events
adverse reactions to the anesthetic or antiseptic solutions
bleeding, including chest wall hematoma formation and hemothorax
Intra-abdominal bleeding from liver or spleen puncture
empyema
seeding the needle tract with underlying tumor

In a meta-analysis of 24 studies that address development of pneumothorax following thoracentesis, a rate of 6.0 percent (95% CI: 4.6% – 7.8%) was noted; 34 percent of pneumothoraces were treated with chest tube insertion (PUBMED:20177035). Use of ultrasound was associated with a significantly lower risk of pneumothorax (odds ratio of 0.3; 95% CI: 0.2 – 0.7). Pneumothorax was more likely when the procedure was performed for therapeutic purposes or when periprocedural symptoms were noted.

When reporting procedure-related pneumothoraces, clinicians are encouraged to distinguish those that arise from needle trauma from those that are due to inexpandable lung (pneumothorax ex vacuo).The latter is more common when ultrasound is used for needle placement.

Retrospective reviews of large interventional radiology databases have demonstrated no evidence of pleural infection or bleeding following thoracentesis, but these studies are limited by non-standardized methods of surveillance for procedure-related complications (PUBMED:21700980, PUBMED:20858808).

What’s the evidence?

Feller-Kopman D. Therapeutic thoracentesis: The role of ultrasound and pleural manometry. Curr Opin Pulm Med 2007;13(4):312-8.

(This review details the utilization of ultrasound and pleural manometry for therapeutic pleural space evacuation. The details of ultrasound technical aspects and outcomes are brief, but extensive details are provided on pleural manometry, including descriptions of normal pleural pressure physiology, lung entrapment versus trapped lung, reexpansion pulmonary edema, and pleural measuring technique.)

Feller-Kopman D. Ultrasound-guided thoracentesis. Chest 2006;129:1709-14.

(This excellent review covers the technical aspects of image acquisition, ultrasonographic features of effusions, procedure approach, and reported outcomes of ultrasound guidance for thoracentesis. This review also includes important practice management implications, such as ultrasound competency and billing.)

Gordon CE, Feller-Kopman D, Balk EM, Smetana GW. Pneumothorax following thoracentesis: A systematic review and meta-analysis. Arch Intern Med 2010;170(4):332-9.

(This systematic review and meta-analysis summarizes the findings of 24 studies of thoracentesis (6,605 total procedures) that report pneumothorax rates. The overall pneumothorax rate is generated to include the frequency of pneumothoraces that require chest tube insertion. The relationship between the measured operator, the patient, and procedure factors and iatrogenic pneumothorax are reported.)

Heidecker J, Huggins JT, Sahn SA, Doelken P. Pathophysiology of pneumothorax following ultrasound-guided thoracentesis. Chest 2006;130(4):1173-84.

(This retrospective study describes the outcome of 401 patients who underwent ultrasound-guided thoracentesis. Post-procedure imaging was used to document unexpandable lung (extremely well defined). For the small cohort of unintentional pneumothoraces (8), pleural elastance, absolute pleural pressure, and symptoms were evaluated for prediction. This study is a “must review” for its exceptional delineations of radiographic trapped lung, pleural elastance measurements, and postulated normal values, and for its expertly written speculation on the etiology of post-drainage pneumothoraces.)

McVay PA, Toy PTCY. Lack of increased bleeding after paracentesis and thoracentesis in patients with mild coagulation abnormalities. Transfusion 1991;31:164-71.

(This retrospective review of 608 patients who underwent paracentesis or thoracentesis with measured coagulation, platelet, and pre- and post-procedure hemoglobin values sought to describe the risk of bleeding associated with these procedures. This article is worthy of review, given that it is often cited as the defense for the safety of these procedures in patients with abnormal platelet and coagulation profiles.)

Yoneyama H, Arahata M, Temaru R, Ishizaka S, Minami S. Evaluation of the risk of intercostal artery laceration during thoracentesis in elderly patients by using 3D-CT angiography. Intern Med 2010;49(4):289-92.

(This retrospective review reconstructed 33 chest CT scans into 3D-CT angiography to describe the position of the intercostal artery. Although limited by scope and design, the study emphasizes the importance of more lateral site selection for thoracentesis and impressive angiogram examples of patients with markedly tortuous intercostal arteries.)

Pleural Biopsy: General description of procedure, equipment, technique

Pleural biopsies are typically performed in evaluating undiagnosed exudative pleural effusions or abnormal pleural thickening. Suspicion of malignancy or infection, particularly tuberculosis, is the most common clinical context. Pleural biopsies are usually performed by pulmonologists, thoracic surgeons, or interventional radiologists. Equipment utilized includes transthoracic needles or a thoracoscope.

Closed pleural biopsies are usually performed by pulmonologists using an Abrams or Cope needle.
Radiology-guided pleural biopsies are typically performed by interventional radiologists who employ a cutting needle.
Thoracoscopically guided biopsies, typically performed by pulmonologists or thoracic surgeons, may include use of flexible forceps (flexi-rigid scope) or rigid tools (rigid thoracoscope). Thoracoscopy is the only one of these techniques that also provides an option for therapy. Pleurodesis may be performed following thoracoscopic biopsies.

Pleural Biopsy: Indications and patient selection

A thoracentesis should be performed in the setting of a pleural effusion that layers more than 1 cm on the lateral decubitus view. Pleural biopsies are often indicated for undiagnosed recurrent pleural effusions, especially when malignancy is a consideration.

Closed pleural biopsies, which were developed in the 1950s, include the Cope and Abram’s needles. Image-guided biopsies have prospered in the past couple of decades. Ultrasound-guided biopsies became more popular in the 1980s. Tru-cut needles were developed in the late 1980s. Thoracoscopy has been present since Jacobeus in 1910. Despite these hundred years, it is more common in larger medical centers.

Thoracentesis has a diagnostic yield of 55-60 percent. One study demonstrated an increased yield by 27 percent with a second thoracentesis, but only an additional 5 percent for the third. If there is high incidence of TB, thoracentesis has high diagnostic yield (90%). If the thoracentesis is negative, consider closed pleural biopsy because the distribution of granulomas is uniform across the pleura.

Ultrasound is a reasonable first test, as it guides thoracentesis and other procedures. If there is pleural thickening, pleural nodularity, or diaphragmatic thickening, malignancy is more likely. Image-guided biopsies of the pleura have a high yield in these cases. For diffuse disease and in cases in which therapy is required, thoracoscopy should be considered for diagnostic purposes since pleurodesis can be achieved in the same setting.

Pleural Biopsy: Contraindications

Contraindications to closed and radiology-guided pleural biopsies include:

Untreated coagulopathy (INR > 1.5)
Uncorrected systemic anticoagulation
Significant thromocytopenia (platelet count < 50,000)
Skin disease at the puncture site
Empyema

Contraindications to thoracoscopy include:

Inability to enter the pleural space because of adhesions
Hypoxemia that cannot be corrected and that is unrelated to the procedure
Pulmonary hypertension
Unstable myocardial status or function
Bleeding diathesis, as described above
World Health Organization performance status greater than 2, unless related to the effusion

Pleural Biopsy: Details of how the procedure is performed

The Cope needles consists of four components: an outer hollow cannula with a cutting edge, a stylet, a hollow blunt trocar, and a hooked biopsy trocar. The procedure is performed as follows:

The stylet is inserted into the blunt trocar.
This two-piece assembly is inserted into the outer cannula.
The skin is cleaned with antiseptic.
The skin and pleura are anesthetized with lidocaine, and the presence of pleural fluid is confirmed.
A small incision is made using a number 11 blade.
The outer cannula/stylet assembly is inserted into the skin over the lower of the two ribs that define the interspace.
The patient is instructed to exhale or to hum, and the stylet/blunt tocar assembly is replaced with the hooked biopsy trocar.
The hook is oriented in a downward direction, and the biopsy trocar is retracted.
The outer cannula is gently advanced in a spiral motion to dislodge the hooked biopsy trocar that contains the tissue sample.
The specimen is processed.
A post-procedure x-ray is obtained to evaluate for pneumothorax.

The operator’s thumb should be placed over the proximal end of the trocar to prevent pneumothorax. The hook needle must be repeatedly withdrawn following each biopsy.

The Abrams needle includes three components: an external trocar, an inner cannula, and a stylet. The trocar, the cannula, and the stylet are combined and inserted into the pleural space. The procedure is performed as follows:

The stylet is replaced with a 60 cc syringe.
The inner cutting cannula is rotated counterclockwise to open the outer notch and aspirate pleural fluid.
The needle is withdrawn with the notch facing downward until tissue is snagged.
The inner cutting cannula is rotated to secure the tissue.
The needle is removed, and the specimen is processed.
A post-procedure x-ray is obtained to evaluate for pneumothorax.

Both Cope and Abrams needles provide a similar diagnostic yield. Four to six biopsy specimens are recommended. Patients are required to hold their breath during the biopsy.

CT-guided biopsies permit access to areas of the pleura that are not readily identified by ultrasound. These include lesions behind the ribs or along paravertebral surfaces. Cross-sectional imaging permits tissue cores to be obtained even when pleural thickening is 55 mm or less. Cutting needle biopsies have a higher yield than the fine needle aspirates do, although a combination of the two may be useful.

Thoracoscopy may be performed using general anesthesia or conscious sedation. Ultrasound is often performed prior to the procedure. The procedure is performed as follows:

The patient is placed in a lateral decubitus position.
The skin is cleansed with antiseptic, and a full sterile field is created with drapes or towels.
1 percent lidocaine is applied to the skin and the pleura as the anesthetic-containing needle and syringe are advanced over the lower rib, defining the interspace.
A 1-2 cm horizontal incision is created in the skin.
A blunt forceps is used to enter the pleural space.
The trocar is advanced.
The thoracoscope is advanced through the trocar. For medical pleuroscopy using a flexi-rigid scope, one port is used. Additional ports are used for rigid pleuroscopy.
The pleural fluid is drained using suction.
Pleural biopsies are obtained under direct visualization.
If indicated, pleurodesis may be performed.
The thoracoscope is removed and replaced with a chest tube.
The chest tube is sutured in place and attached to suction.
A post-procedure chest x-ray is obtained.

Pleural Biopsy: Interpretation of results

In the setting of suspected tuberculosis, the finding of granulomatous inflammation is sufficient reason to begin treatment. Long-term follow-up after a diagnosis of non-specific pleuritis demonstrates that 5-25 percent of patients are eventually diagnosed with malignant pleuritis. The incidence was 15 percent in the largest study. Therefore, most patients with biopsies that are negative for malignancy should receive clinical and radiographic follow-up.

Pleural Biopsy: Performance characteristics of the procedure (applies only to diagnostic procedures)

When thoracentesis is nondiagnostic in the setting of an exudative effusion suspected of malignancy, performance of closed pleural biopsy increases the diagnostic yield by 7 percent over pleural fluid cytology alone. The sensitivity of combining thoracentesis and closed pleural biopsy approaches 79 percent in the diagnosis of malignant disease and 71-88 percent in tuberculosis.

Closed pleural biopsy – less than 60 percent
Ultrasound-guided biopsy – 83 percent
CT-guided biopsy – 88 percent
Thoracoscopy – 91-95 percent

In establishing a diagnosis of malignancy, the sensitivity varies according to the procedure performed:

Pleural Biopsy: Outcomes (applies only to therapeutic procedures)

Of the techniques for pleural biopsy, only thoracoscopy provides a therapeutic role. Although several agents are possible for pleurodesis, talc insufflation provides the highest yield. Thoracoscopy can provide a diagnosis 90-95 percent of the time and successful pleurodesis more than 90 percent of the time.

Pleural Biopsy: Alternative and/or additional procedures to consider

As described in the text, pleural biopsies may be performed using several different techniques.

Pleural Biopsy: Complications and their management

Complications of closed pleural biopsy include:

Site pain (< 15%)
Vasovagal reaction with syncope (< 5%)
Hemothorax (< 2%)

Complications of transthoracic needle biopsy, which occur at a rate of under 5 percent, include:

Pneumothorax
Bleeding
Diaphragm damage
Hematoma (< 1%)

Complications of thoracoscopy include:

Hemorrhage (2-3%)
Empyema (2-3%)
Death (0.04%)
The incidence of minor complications is 2-6 percent; included are fever, subcutaneous emphysema, re-expansion pulmonary edema, bleeding, and seeding of the chest wall with tumor.
Hematoma (< 1%)

Pleural Biopsy: What’s the evidence?

Garcia LW, Ducatman BS, Wang HH. The value of multiple fluid specimens in the cytological diagnosis of malignancy. Mod Pathol. 1994;7(6):665-668.

(Of 215 patients with 570 specimens submitted, the diagnosis of malignancy in pleural fluid was made with the first thoracentesis 65 percent of the time. The diagnosis was made on the second specimen 27 percent of the time and in the third specimen 5 percent of the time. The authors concluded that the majority of malignant effusions are detected with two specimens and that the examination of more than three specimens is of little value.)

Janssen JP. Why you do or do not need thoracoscopy. Eur Respir Rev. 2010;19(117):213-216.

(This review explains the evaluation for the undiagnosed exudative pleural effusion. Focus is on four techniques: closed pleural biopsy, image-guided biopsy (by ultrasound or CT-guidance), and thoracoscopy. The use of closed pleural biopsies should be limited to areas where tuberculosis is highly suspected and medical resources are limited. Both ultrasound- and CT-guided biopsies have a high diagnostic yield and, in appropriately trained-hands, provide a very good approach for pleural biopsies. Thoracoscopy is the only technique that provides both a high diagnostic yield and the possibility of performing therapy via pleurodesis at the same time.)

Morrone N, Algranti E, Barreto E. Pleural biopsy with Cope and Abrams needles. Chest. 1987;92(6):1050-1052.

(In this prospective study, 84 closed pleural biopsies were performed. For cases that ultimately were confirmed to be malignant, four specimens were required to have the highest yield. There was an increase from 54 percent to 89 percent from the first to the fourth specimen for carcinoma. On the other hand, only one high-quality biopsy was required to attain an 81 percent sensitivity for the diagnosis of tuberculosis. As such, it was concluded that one specimen was required for tuberculosis but four were required when performing closed pleural biopsies to diagnose carcinoma.)

Jimenez D, Perez-Rodriguez E, Diaz G, Fogue L, Light RW. Determining the optimal number of specimens to obtain with needle biopsy of the pleura. Respir Med. 2002;96(1):14-17.

(In this prospective study, 84 patients underwent closed pleural biopsy using a Cope needle. Five biopsies were obtained and analyzed for histology (specimens 1-4) and microbiology (specimen 5). With individual biopsies, the diagnostic yield increased from 44 percent to 58 percent when all specimens were analyzed, rather than just one. For malignancy, the diagnostic yield improved from 55 percent to 89 percent when all samples were reviewed. For tuberculosis, there was a high diagnostic yield (81%) with the first biopsy, and additional biopsies did not improve the yield significantly. In summary, this study suggests that only one biopsy is needed when tuberculosis is high on the differential diagnosis, whereas four pleural biopsies improve the diagnostic yield in other conditions.)

Thoracic Ultrasound: General description of procedure, equipment, technique

Thoracic ultrasound may be utilized for the diagnostic evaluation of pneumothorax, parenchymal lung injury, or pleural space abnormalities, including effusions, scarring, masses, and nodules. Bedside imaging may be used to guide procedures, including thoracentesis, chest tube thoracostomy, and transthoracic needle biopsy. The technique has been demonstrated to provide superior procedural guidance when compared with physical examination alone.

In imaging the pleura, ultrasound confers advantages over traditional radiographic imaging that include maximal portability, real-time and dynamic imaging, and the absence of radiation.

To realize the benefits of thoracic ultrasonography, the clinician must undergo focused, supervised training to ensure accurate interpretation of normal and pathologic anatomical structures and ultrasound air artifacts.

Thoracic Ultrasound: Indications and patient selection

There are several indications for bedside thoracic ultrasound. Ultrasound is substantially better than physical examination in site selection for thoracentesis. Ultrasound should be utilized in all cases when the appropriate equipment and operator experience are available.

Thoracic ultrasound is particularly helpful as a diagnostic tool for the critically ill patient because diagnostic information on critical conditions, such as pneumothorax, lung consolidation, pleural effusion, and pulmonary edema, can be ascertained. Furthermore, ultrasonography has demonstrated superior sensitivity compared with the plain chest radiograph in detecting the presence of pleural fluid and pneumothorax and in differentiating pleural fluid from lung consolidation. Although ultrasound is inferior to CT for complete imaging of the thorax, it eliminates the transport risk and resource utilization associated with off-site CT examination.

Delineation of pleural fluid as a cause for decreased breath sounds or opacificaton on the plain chest radiograph
Delineation of pleural fluid complexities, including loculations, scarring, masses, and nodules
Detection of pneumothorax
Provision of guidance for bedside pleural procedures, including thoracentesis, chest tube thoracostomy, and transthoracic needle biopsy

Contraindications: Thoracic Ultrasound:

Although thoracic ultrasound may provide important clinical information, its value depends on operator sophistication for proper image acquisition and interpretation. Comprehensive, supervised training is necessary to ensure correct interpretation of sonographic findings.

Thoracic Ultrasound: Details of how the procedure is performed

Thoracic ultrasound may be performed with most ultrasound machines that have two-dimensional scanning capability. Transducers with frequencies between 3 and 5 MHz and a small footprint, such as sector scanning or convex array transducers, are optimal, given the necessity of imaging between ribs. These convex transducers provide a good compromise between near-field resolution and penetration for deeper structures.

Higher frequency (7.5 to 10 MHz) linear transducers, usually used for vascular evaluations, may provide additional detail of superficial structures. However, these transducers are limited by depth of penetration and fit between the rib spaces when used in longitudinal scanning in a slender individual.

Digital image storage is optimal for recording dynamic images that can be transferred to a repository for durable review. A printer aids in the creation of a hard copy for placement in the chart, but use of hard-copy printouts limits interpretation to a single, static image.

Concluding the scanning procedure: Prior to ultrasound, other chest imaging should be reviewed to confirm the expected side, the relative side, and the size of the pleural effusion. Potential complexities of the pleural space should be noted, including the suggestions of loculation or pleural masses or nodules.

Patient, operator, and machine positions should be carefully selected. The machine and the site of interrogation should be present simultaneously in the operator’s field of vision, and the working space should be comfortable. For thoracentesis, the patient should be seated upright, with his or her arms extended and raised to shoulder level. The patient’s back should be fully accessible. Such positioning permits maximal basilar lung displacement by pleural fluid (when free-flowing) adjacent to the sonographically distinct diaphragm. Gravity further aids full evacuation of the fluid, as needed.

Suboptimal positioning may be necessary in frail, comatose, or critically ill patients tethered to support devices (see above). Regardless, ultrasound localization should be performed with the patient in the same position that he or she will assume during the procedure. The advantages of ultrasound site selection are diminished if ultrasound is used to mark a puncture site and the patient’s position subsequently changes.

In contrast, when evaluating for pneumothorax, the patient should lie supine, thereby facilitating visualization of free pleural air in the anterior chest.

Acoustic gel should be applied to the patient’s skin where the transducer will rest, providing an airless interface and easy movement of the probe.

Scanning is begun with the application of a 3.5-5.0 MHz convex transducer applied perpendicular to the chest wall as the operator’s hand is gently anchored against the patient. By convention, the screen marker should be in the upper left of the screen. The transducer notch or groove that correlates with the screen marker should be pointed cephalad (Figure 1).

Tumor nodules seen on the pleura. Because they are non-uniform, closed pleural biopsies may miss the diagnosis.

The transducer is then moved longitudinally from one interspace to another. The thorax should be divided into multiple scan lines; commonly employed scan lines include anterior (bordered by the sternum and anterior axillary line), lateral (in mid-axillary line), and posterior (bordered by posterior axillary and mid-scapular lines).

After a general examination, the examiner may focus on an area of particular interest, utilizing multiple scanning axes to develop a cognitive three-dimensional picture. A higher frequency linear transducer permits more detailed imaging of superficial structures (e.g., lung sliding in the evaluation of pneumothorax or assessment of potential vessels for use for device insertion).

For thoracentesis, the distance from skin to chest wall and the distance from parietal pleural surface to lung should be measured to estimate aspiration depth and guide equipment selection. Pressure from probe application may result in an underestimation of the chest wall thickness.

Thoracic Ultrasound: Interpretation of results

Understanding of the ultrasound appearance of normal anatomic structures is necessary.

Chest wall and pleural line (Figure 2)

The intercostal muscles appear as hypoechoic, linear shadows of soft tissue density that contain echogenic fascial planes. The superficial surfaces of the ribs appear as echoic curvilinear edges with posterior acoustic shadows (hypoechoic zone). The pleural line is a hyperechoic, roughly horizontal line located approximately 0.5 cm below the rib line; it is less than 2 mm wide, and it reflects the interface between the soft tissues (rich in water) of the chest wall and lung tissue (rich in air). All lung signs arise at the level of the pleural line, with observations there demonstrating a “twinkling” phenomenon in rhythm with respiration. This appearance is generated by the sliding of the visceral pleura (attached to the lung) against the parietal pleura (attached to the chest wall), given the inspiratory descent of the lung toward the abdomen. “Lung sliding” indicates adherence of the visceral pleura to the parietal pleura, as the movement disappears when air is present between pleural layers (i.e., pneumothorax). The amplitude of lung sliding normally increases from apex to base.

Diaphragm (Figure 3)

The diaphragm, a strong reflector of ultrasound waves, should be identified early to define the lower border of the thoracic space. The diaphragm is usually recognized as a large, hyperechoic, concave structure, approximately 1 mm thick, which descends caudally during inspiration. The diaphragm is optimally visualized through the lower intercostal spaces, usually below the ninth rib, by using the liver or spleen as an acoustic window. Scatter of ultrasound waves by aerated lung prevents visualization of the diaphragm distinct from more superior intercostal spaces. In contrast, the diaphragm is readily visualized when a pleural effusion creates a fluid interface.

Heart

Three traditional views of the heart can be ascertained from the subcostal, parasternal, and apical approaches (limited view echo). Ultrasound surveillance of the heart is important when performing needle insertion in the left anterolateral thorax. Intercostal views of the heart from the posterior and lateral positions is possible with cardiomegaly, mediastinal shift, or the presence of a fluid-rich interface (e.g., in the presence of pleural fluid or lung consolidation).

Lung

The appearance of the lung varies based upon the lung region’s composition of air and fluid. Sonographic artifacts caused by air-tissue interfaces are important to understand, as they aid in the diagnosis of lung and pleural diseases. Normal, edematous, and consolidated lungs present distinctive ultrasound appearances, while normal, aerated lung (Figure 4) has an ultrasound appearance of grainy, bright echoes (air generates scatter of ultrasound waves). Aerated lung produces a characteristic artifact–designated “A lines”. These are roughly horizontal, hyperechoic lines that are parallel to the pleural line and arise below it at a distance that recreates the interval between the skin and pleural line. Several A lines are often visible at regular intervals. They represent reverberation artifacts from ultrasound reflection between the pleural surface and the outer surface of the chest wall. If lung sliding is present, A lines are consistent with normal aeration.

Diaphragm and Sub-diaphragmatic structures

Edematous lung (Figure 5) has a characteristic pattern of air artifact–designated “B lines”. These vertical artifacts arise from the pleural line, appear like a narrow, laser ray or “comet tail,” and extend to the edge of the screen without fading; they obliterate A lines and generally synchronize with lung sliding. Several B lines visible in a single scan have been termed “lung rockets.” B lines are caused by a ring-down artifact derived from small supleural fluid collections or tissue densities. B lines associated with lung sliding generate a pendulum appearance that facilitates recognition of sliding, and they are strong evidence against pneumothorax. Normal individuals may have a few B lines in the lower lateral chest.

Consolidated lung (Figure 6) takes on a tissue appearance under ultrasound. Its echogenic similarity to liver prompts the term “hepatization of the lung.” Air bronchogram equivalents may be visualized as hyperechoic foci (caused by small amounts of air within the bronchi). Lung compressed from a surrounding pleural effusion appears tissue-dense (hyperechoic), exhibits a characteristic flapping motion (akin to a sail), and moves with the respiratory cycle. Multiple B lines may be seen at the border of aerated and compressed lung.

Pleural Effusion (Figure 7)

Pleural fluid appears as anechoic or hypoechoic compared to the liver. In general, identification of pleural fluid includes three key characteristics: a relatively echo-free space within the thoracic cavity; usual anatomic boundaries surrounding the proposed effusion, including the chest wall (proximal), the diaphragm (caudal), subdiaphragmatic structures (liver and spleen), and the surface of the lung (deep); and evidence of respiratory cycling (diaphragm movement, lung movement), with resulting deformation of the shape of the pleural effusion.

The identification of a pleural effusion may be complicated by patient and pleural disease factors. Chest wall edema or obesity may degrade image quality and make identification of structures problematic. Applying firm pressure with the transducer may help improve image quality, but this approach makes distance measurements problematic. Complex effusions may be localized or most accessible in a non-dependent area of the thorax, so scanning near the diaphragm alone is insufficient. Complex effusions may have swirling echoes, strands, fronds, or septations (Figure 8, Figure 9). Hemothorax and empyema may be homogenously echogenic (isoechoic to the liver or spleen) with diffuse internal echoes.

Small effusion with consolidate lung and B lines

Pneumothorax

Suggestive findings:

Lung sliding is absent (in contradistinction to the equivalent site over the contralateral lung or in a region that previously exhibited sliding, such as following a procedure). M Mode can be used to demonstrate the presence or absence of lung sliding with a still image. The “seashore sign” is the equivalent of lung sliding in 2D mode, describing the granular pattern that underlies the horizontal motionless layers of the chest wall on M-mode. The straight, motionless aspect depicts the stationary chest wall (‘waves’) that lie above the granular layer (‘beach”), which indicates respirophasic movement of the lung (Figure 10). The “barcode sign” is the equivalent of absent lung sliding and reverberation artifact in 2D mode imaging suggesting pneumothorax (Figure 11).

Seashore Sign. Pleural sliding evidenced on M mode

Barcode sign. The absence of pleural sliding in M Mode suggesting pneumothorax

B lines are not observed.

Confirmatory finding: The lung point is observed. In the case of a pneumothorax without total lung collapse, regions of lung and parietal pleura will remain adherent to the parietal pleura. The areas where these collapsed and adherent lungs are juxtaposed is termed the “lung point.” This appears as a region with intermittent lung sliding because the collapsed lung (to some extent) still inflates synchronously with the respiratory cycle (Figure 12). Determination of this finding requires both a comprehensive screen and experienced operator. A lung point is not evident in pneumothorax with total lung collapse.

Lung Point. Confirmatory finding in pneumothorax

Malignant diaphragmatic pleural nodule from metastatic cholangiocarcinoma

Thoracic Ultrasound: Performance characteristics of the procedure (applies only to diagnostic procedures)

The performance characteristics for ultrasound in a variety of clinical settings can be summarized as follows:

Diagnostic ultrasound: The diagnostic accuracy of ultrasound is 93 percent for pleural effusion, 97 percent for alveolar consolidation, and 95 percent for alveolar-interstial syndrome when compared to standard chest CT scans. Diagnostic accuracy far exceeds that of physical examination and portable chest radiography (PUBMED:14695718).

Thoracentesis: Ultrasound is substantially better at determining the location of pleural fluid than is physical examination. In a study that compared site selection by physical examination with site selection by ultrasound as the “gold standard,” 25/172 (15%) of sites localized by physical examination were found to be inaccurate (PUBMED:12576363). In 83 cases without a determined site by physical examination, ultrasound demonstrated a safe needle access site (>10 mm in diameter) 54 percent of the time. Sensitivity and specificity were 77 percent and 60 percent (positive predictive value, 86%; negative predictive value, 46%), respectively, for identifying a proper puncture site when clinical examination was compared with ultrasound. Experienced physicians did not perform better on clinical examination than did physicians in training. In addition, ultrasound guidance increases the likelihood of a successful tap over guidance by physical examination alone. (PUBMED:7962588)

Pneumothorax: Bedside ultrasound performance characteristics have been demonstrated to be highly variable (49%-100%). However, bedside ultrasound appears to have a higher sensitivity for detecting pneumothorax compared with chest radiographs (using CT scanning as the gold standard). For example, in a series of 176 trauma patients, the sensitivity of bedside ultrasound was 98 percent versus 76 percent for the supine portable chest radiograph, (PUBMED:16141018) The technique’s specificity is not significantly different from that of chest radiography, ranging from 94 percent to 100 percent. In addition, the presence of lung sliding on ultrasound has been reproducibly demonstrated to have a negative predictive value greater than or equal to 99 percent in ruling out pneumotrax in multiple studies of critically ill patients and in trauma victims. Although the presence of lung sliding excludes pneumothorax, the absence of lung sliding has a sensitivity of only 95 percent and a specificity of 91 percent for pneumothorax. Therefore, the absence of lung sliding does not confirm the presence of pneumothorax.

Thoracic Ultrasound: Alternative and/or additional procedures to consider

Although more sensitive than chest radiography under certain conditions, ultrasound is not superior to CT for comprehensive diagnostic imaging of the chest. Complex pleural and lung parenchymal diseases, the presence of excessive chest wall thickness, and obesity may limit ultrasound interpretation. Ultrasound serves as a secondary option when patient management is constrained by clinical instability and patient transport creates substantial risk. Similarly, ultrasound guidance is not as good as guidance by CT imaging for complicated, interventional pleural procedures, such as empyema drainage using a pigtail catheter or biopsy of a pleural mass.

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