Pericardial effusion: Approach to diagnosis

INTRODUCTION — The pericardium is a fibroelastic sac surrounding the heart that contains a thin layer of fluid. A pericardial effusion is considered to be present when accumulated fluid within the sac exceeds the small physiologic amount (15 to 50 mL). An approach to pericardial effusion, including identification and management, is presented here.

Related issues are discussed separately:

●(See "Etiology of pericardial disease" and "Acute pericarditis: Clinical presentation and diagnosis" and "Pericardial disease associated with cancer: Clinical presentation and diagnosis" and "Purulent pericarditis" and "Tuberculous pericarditis" and "Post-cardiac injury syndromes" and "Pericardial complications of myocardial infarction".)

●(See "Management of pericardial effusion and acute pericarditis during pregnancy" and "Pericardial disease associated with cancer: Management".)

WHEN TO SUSPECT PERICARDIAL EFFUSION — Pericardial effusion should be suspected in the following clinical settings, particularly in patients with any of the disorders known to involve the pericardium (table 1). (See "Etiology of pericardial disease", section on 'Pericardial effusion'.)

Urgent conditions — Diagnosis and management of pericardial effusion is most urgent for patients with cardiac tamponade. Purulent pericarditis also requires urgent identification and treatment.

●Cardiac tamponade – Cardiac tamponade is caused by pericardial fluid accumulating under pressure, impairing cardiac filling and reducing stroke volume. Tamponade is suspected based upon the patient's history (which may include a cause of pericardial disease or effusion (table 1 and table 2)), symptoms (eg, fatigue, dyspnea, syncope, presyncope), and signs. Nearly all patients with cardiac tamponade have one or more of the following physical findings (see "Cardiac tamponade", section on 'Clinical presentation'):

•Sinus tachycardia – This nonspecific sign is seen in nearly all patients with cardiac tamponade, while hypotension is more variably present. In the setting of cardiac tamponade, sinus tachycardia is a sign of hemodynamic compromise, which should be urgently treated with pericardial fluid drainage.

•Elevated jugular venous pressure – This finding is seen in nearly all patients with cardiac tamponade. Peripheral edema may also be present. However, patients who are severely hypovolemic may present with low pressure tamponade, which is associated with low jugular venous pressure. (See "Cardiac tamponade", section on 'Low-pressure cardiac tamponade'.)

•Pulsus paradoxus – This finding is defined as an abnormally large decrease in systolic blood pressure (>10 mmHg) on inspiration. It is a common finding in moderate to severe cardiac tamponade and is a direct consequence of ventricular interdependence (waveform 1 and waveform 2 and waveform 3). (See "Pulsus paradoxus in pericardial disease".)

•Hemodynamic deterioration – Cardiac tamponade is one of the causes of hemodynamic instability and should be suspected, particularly in patients with a condition that may involve the pericardium (eg, ascending aortic dissection). (See "Clinical features and diagnosis of acute aortic dissection", section on 'Hypotension'.)

The diagnosis and management of cardiac tamponade, including urgent pericardial fluid removal, are discussed separately. (See "Cardiac tamponade".)

●Purulent pericarditis – This condition typically presents with high fever and tachycardia, with or without chest pain. A high index of suspicion is required, particularly in patients with a known infection that may seed or spread to the pericardium or prior perforating injury of the pericardium. Urgent diagnosis and management is required, as discussed separately. (See "Purulent pericarditis".)

Other clinical settings — An evaluation for pericardial effusion is also indicated in patients with the following findings or conditions:

•All cases of acute pericarditis. (See "Acute pericarditis: Clinical presentation and diagnosis", section on 'Diagnostic evaluation'.)

•Unexplained low voltage on the electrocardiogram (ECG). (See 'ECG findings' below.)

•Unexplained new radiographic cardiomegaly, particularly when present without pulmonary congestion. (See 'Chest radiograph' below.)

•Presence of isolated left (or left larger than right) pleural effusion [1].

Additional clinical presentations that may suggest pericardial effusion are discussed below (see 'Clinical presentation' below). Also, a pericardial effusion may be detected as an incidental finding on imaging (eg, echocardiography or computed tomography [CT]) performed to evaluate another condition.

Clinical presentation — The following clinical findings occur in patients with pericardial effusion with or without cardiac tamponade.

Symptoms and signs — Patients with pericardial effusion may experience chest pain or fullness. However, many patients with pericardial effusion without tamponade have no symptoms or signs directly caused by the pericardial effusion, although they may have symptoms related to the underlying cause of pericardial disease (eg, fever in the setting of infectious or immune-mediated pericarditis). Thus, pericardial effusions are often discovered incidentally during evaluation for other cardiopulmonary diseases.

In the absence of cardiac tamponade, physical signs of pericardial effusion are so insensitive and nonspecific that they are of historic rather than practical interest. As an example, the ability to percuss cardiac dullness beyond the apical point of maximal impulse is consistent with pericardial effusion, but it depends upon the absence of disease of the lower lobe of the left lung or left pleura and the expertise of the examiner. Ewart sign (which includes a triangular area of dullness at the tip of the left scapula along with tubular breath sounds and egophony at the same location) suffers from similar limitations [2].

Initial test findings — The presence of a pericardial effusion may be suggested by the ECG or chest radiograph.

ECG findings — An ECG should be performed in patients with suspected pericardial disease. The most common ECG findings in patients with a pericardial effusion are sinus tachycardia, low QRS voltage, and electrical alternans. If pericarditis is present, the ECG findings typical of that disorder (such as ST elevation and PR depression) are also seen (waveform 4). (See "Acute pericarditis: Clinical presentation and diagnosis", section on 'Electrocardiogram'.)

●Sinus tachycardia – Sinus tachycardia (sinus rhythm with rate >100 beats per minute) is a nonspecific sign that is common in patients with pericardial effusion, particularly those with cardiac tamponade. In a study of ECG findings in 241 patients with moderate or large pericardial effusion, sinus tachycardia was present in 43 of 64 patients (67 percent) with cardiac tamponade and 41 of 160 patients (26 percent) without tamponade [3].

●Low QRS voltage – Low QRS voltage is common in patients with pericardial effusion. Low QRS voltage may be observed in the limb leads and/or precordial leads. Low QRS voltage in the limb leads (waveform 5) is present when the amplitudes (nadir to peak) of the QRS complexes in each of the six limb leads is less than 5 mm (0.5 mV). Low voltage in the precordial leads is present when the amplitude in each these leads is less than 10 mm (1 mV).

While the frequency of low voltage appears to be higher among patients with cardiac tamponade than among other patients with pericardial effusion, the presence of low voltage is not specific for cardiac tamponade. In the above-cited study of ECG findings in 241 patients with moderate or large pericardial effusion, low voltage in limb and/or precordial leads was present in 66 percent of patients with cardiac tamponade and in 34 percent of patients without cardiac tamponade [3]. Low voltage is more common with moderate or large pericardial effusions than with small effusions (eg, 83 versus 13 percent in one series [4]).

The combination of low voltage and sinus tachycardia should raise concern about pericardial effusion with cardiac tamponade. However, the combination of low voltage and sinus tachycardia is not specific to patients with pericardial effusion, as this combination of findings may also be seen in patients in a variety of clinical settings, such as chronic obstructive pulmonary disease, pleural effusion, cardiomyopathy, and prior cardiac surgery (table 3).

●Electrical alternans – Electrical alternans is an ECG finding that is observed in some patients with pericardial effusion, particularly those with cardiac tamponade. Electrical alternans is characterized by beat-to-beat alternating amplitude of the QRS complexes (and more subtly of other waveforms) that reflects swinging of the heart in the pericardial fluid (waveform 6 and movie 1). The pattern is usually most apparent in one or more of the precordial leads. (See "ECG tutorial: Miscellaneous diagnoses", section on 'Electrical alternans'.)

Electrical alternans (waveform 6) with sinus tachycardia is a highly specific sign of pericardial effusion, usually with cardiac tamponade, but is only modestly sensitive. As a result, its absence does not exclude cardiac tamponade. In the above-cited study of ECG findings in 241 patients with moderate or large pericardial effusion, electrical alternans was observed in 35 percent of patients with cardiac tamponade and in only 7 percent of patients without tamponade [3].

In contrast, QRS alternans with other tachycardias (eg, paroxysmal supraventricular tachycardias or ventricular tachycardia) is a nonspecific finding resulting from alternation in conduction on a beat-to-beat basis, not from mechanical movement of the heart.

Chest radiograph — A chest radiograph performed in patients with suspected pericardial effusion may identify findings (such as pleural effusions, lung disease, hilar masses, or mediastinal widening) related to the cause of pericardial effusion [5].

However, an enlarged cardiac silhouette on chest radiograph is neither a sensitive nor specific sign of pericardial effusion or cardiac tamponade. The findings on chest radiograph in patients with pericardial effusion are variable, depending on the etiology and size of the pericardial effusion and underlying comorbidities. Small to moderate effusions (less than 200 to 300 mL) are generally not associated with significant findings on the chest radiograph [5], while larger pericardial effusions typically present with an enlarged cardiac silhouette with clear lung fields (image 1).

Cardiac biomarkers — Among patients with pericardial effusion, cardiac biomarkers (eg, serum troponin) may be elevated in those in whom the effusion occurs in association with acute myopericarditis or myocardial infarction. Troponin elevations, typically modest, may occur in association with a variety of other acute illnesses. (See "Elevated cardiac troponin concentration in the absence of an acute coronary syndrome" and "Acute pericarditis: Clinical presentation and diagnosis", section on 'Cardiac biomarkers' and "Myopericarditis".)

DIAGNOSTIC APPROACH — Once a pericardial effusion is suspected, the diagnostic approach includes the following three steps:

●Identify and assess the pericardial effusion – A pericardial effusion is generally diagnosed by echocardiography, with additional cardiac imaging performed only in selected cases, as discussed below. (See 'Cardiac imaging' below.)

●Assessing its hemodynamic impact – Once it is determined that a pericardial effusion is present, the next step is to determine if cardiac tamponade is present, as this is a cause of hemodynamic instability and requires urgent pericardial drainage. (See 'Urgent conditions' above and "Cardiac tamponade".)

●Diagnostic evaluation – After a pericardial effusion has been identified, evaluation is performed to determine its cause. (See 'Clinical presentation' above.)

CARDIAC IMAGING — An echocardiogram is the key diagnostic test for pericardial effusion [5]. Additional cardiac imaging with cardiac computed tomography (CT), cardiovascular magnetic resonance (CMR) imaging, and cardiac catheterization is reserved for patients in selected clinical settings, as discussed below.

Effusion types — A pericardial effusion may be free-flowing or loculated:

●Free-flowing effusion – (See 'Effusion size' below.)

●Loculated – When a pericardial effusion becomes loculated (regional or compartmentalized) it may not be visible in standard echocardiographic views. In some cases, it may be best appreciated in subcostal or transesophageal echocardiographic views, or by cardiac CT or CMR. In other cases (eg, cardiac tamponade early after cardiac surgery), a loculated hematoma may be identified by surgical exploration [6].

Echocardiography

Identifying the effusion — Most pericardial effusions are diagnosed on transthoracic echocardiogram (TTE). Two-dimensional (2D) echocardiography is both sensitive and specific for the detection of pericardial effusion and also provides information regarding the hemodynamic significance of the effusion (ie, identification of cardiac tamponade). (See 'Hemodynamic effects' below and "Echocardiographic evaluation of the pericardium".)

Pericardial fluid appears on an echocardiogram as an echolucent space between the pericardium and the epicardium. Physiologic pericardial fluid (25 to 50 mL) is generally visible only during ventricular systole. A significant pericardial effusion (exceeding 25 to 50 mL) is identified as an echo-free space throughout the cardiac cycle. (See "Echocardiographic evaluation of the pericardium", section on 'Normal appearance on echocardiographic imaging' and 'Effusion size' below.)

While M-mode echocardiography can identify an effusion (image 2), 2D echocardiography permits a better estimate of the size of the effusion, its distribution, and its distance from potential pericardiocentesis sites.

Effusion size — Pericardial effusion size is assessed and monitored in patients with pericardial effusion, although pericardial size alone does not determine its hemodynamic significance. (See "Pericardial effusion: Approach to management", section on 'General management' and 'Hemodynamic effects' below.)

Although 2D echocardiography cannot precisely quantify pericardial effusion size (which is better quantified by cardiac CT or CMR), a common approach is to grade free-flowing effusions as small, medium, or large as determined by the size of the echo-free space surrounding the heart. The site of fluid accumulation for a free-flowing effusion is positional due to gravity dependence.

●Small effusions (50 to 100 mL) are typically only seen posteriorly and are generally less than 10 mm wide, causing minimal separation between the epicardial (visceral) pericardium and the thicker parietal pericardial sac. A small free-flowing pericardial effusion is typically identified on echocardiography above the right atrium in the apical four-chamber view with the patient in the left lateral decubitus position (image 3).

●Moderate effusions (100 to 500 mL) are generally seen along the length of the posterior wall but not anteriorly; the echo-free space is 10 to 20 mm at its greatest width.

●Large effusions (>500 mL) are generally seen circumferentially (movie 2 and image 4 and image 5); the echo-free space is greater than 20 mm at its greatest width.

Hemodynamic effects — The diagnosis of cardiac tamponade is based largely upon clinical and imaging (primarily echocardiographic) findings, although definitive confirmation of the diagnosis is made by hemodynamic assessment via cardiac catheterization during pericardial fluid drainage. (See "Cardiac tamponade", section on 'Diagnosis'.)

With cardiac tamponade, the pericardial effusion is commonly moderate or large (movie 1), but may be small if the effusion has accumulated rapidly. The speed of pericardial fluid accumulation affects the size of pericardial effusion that causes cardiac tamponade (figure 1). The normal pericardium can stretch to accommodate increases in pericardial volume, with the amount of stretch related to the period of time over which the pericardial effusion accumulates, as discussed separately. (See "Cardiac tamponade", section on 'Pathophysiology'.)

Echocardiographic features of cardiac tamponade include (see "Cardiac tamponade", section on 'Echocardiogram'):

●Collapse of the right atrium at end-diastole and the right ventricle in early diastole (movie 3 and movie 4).

●Reciprocal changes in left and right ventricular volumes with respiration, which are important in the pathogenesis of pulsus paradoxus (figure 2). (See "Pulsus paradoxus in pericardial disease".)

●Increased respiratory variation of mitral and tricuspid valve inflow velocities (increase in mitral flow by 30 percent and decrease in tricuspid valve flow by 60 percent on the first beat of expiration).

●Dilation (plethora) of the inferior vena cava and less than a 50 percent reduction in its diameter during inspiration, reflecting systemic congestion (image 6 and image 7).

The diagnosis and management of cardiac tamponade are discussed in detail separately. (See "Cardiac tamponade".)

Cardiac CT and CMR — Imaging with cardiac CT or CMR is reserved for patients with nondiagnostic echocardiographic evaluation who require further assessment to identify and examine a pericardial effusion (eg, suspected loculated effusion) or to identify other suspected pericardial pathology (eg, constrictive pericarditis or a pericardial mass). (See "Constrictive pericarditis: Diagnostic evaluation", section on 'Additional testing' and "Pericardial disease associated with cancer: Clinical presentation and diagnosis", section on 'Further cardiac imaging'.)

Cardiac CT or CMR is helpful in identifying, characterizing, and quantifying a pericardial effusion and also identifying other pericardial findings such as pericardial thickening and pericardial tethering (which are associated with constrictive pericarditis) [7,8]. In patients who are hemodynamically unstable, cardiac CT is generally preferred to CMR. (See 'Differential diagnosis' below and "Constrictive pericarditis: Diagnostic evaluation", section on 'Additional testing'.)

In some cases, pericardial effusion may be first detected by CT, especially when CT is used to detect pulmonary embolus, a more common cause of shortness of breath and hypotension.

CARDIAC CATHETERIZATION — Hemodynamic assessment via cardiac catheterization is generally reserved for patients (usually with suspected cardiac tamponade) undergoing pericardial fluid drainage. When feasible, the diagnosis of cardiac tamponade is confirmed by identifying typical hemodynamic findings prior to pericardial fluid removal and resolution of hemodynamic abnormalities after drainage. (See "Cardiac tamponade", section on 'Cardiac catheterization'.)

DIFFERENTIAL DIAGNOSIS — The differential diagnosis of pericardial effusion suspected on echocardiography includes epicardial fat (commonly visualized anterior to the right ventricular free wall and in the interventricular and atrioventricular grooves) and pleural effusion. These entities can usually be distinguished from pericardial effusion by careful review of the echocardiogram. Epicardial fat may be identified by the presence of faint linear striations within it. A key landmark for posterior pericardial effusion is that it tracks anterior to the descending aorta. If echocardiographic findings are nondiagnostic, cardiac CT or CMR can distinguish these entities. (See "Echocardiographic evaluation of the pericardium", section on 'Normal anatomy' and "Echocardiographic evaluation of the pericardium", section on 'Differentiating between pleural and pericardial effusions'.)

IDENTIFYING THE ETIOLOGY — The cause of the effusion is investigated by clinical evaluation (history, physical examination, blood tests) and in some cases by evaluation of pericardial fluid with or without pathologic examination of the pericardium (algorithm 1).

The cause of a pericardial effusion may be apparent or suspected based upon the clinical setting in which it occurs. Examples include suspected cardiac perforation complicating an invasive procedure, breast or lung cancer, a recent myocardial infarction, severe hypothyroidism, or end-stage kidney disease. (See "Invasive diagnostic cardiac electrophysiology studies", section on 'Complications of invasive cardiac electrophysiology studies' and "Pericardial disease associated with cancer: Clinical presentation and diagnosis" and "Post-cardiac injury syndromes" and "Overview of the management of chronic kidney disease in adults", section on 'Pericarditis' and "Clinical manifestations of hypothyroidism", section on 'Cardiovascular system' and "Clinical manifestations of hypothyroidism".)

When the cause of pericardial effusion is not apparent, evaluation starts with a clinical assessment but may require sampling of the pericardial effusion and/or the pericardial tissue for laboratory analysis. The frequency of different causes of pericardial effusion varies in published reports, depending in part upon the patient population (location and clinical features), as well as the aggressiveness with which an underlying diagnosis was sought (table 2) [9-12]. (See "Etiology of pericardial disease".)

In many cases, the specific etiology of a pericardial effusion cannot be established even when fluid and/or pericardial tissue is analyzed. The likelihood of establishing a specific cause appears to be greater with larger effusions. In series of patients with acute pericarditis (including those with small or undetectable effusions), the underlying diagnosis was established in only approximately 15 to 20 percent [13,14]. In contrast, studies confined to moderate to large pericardial effusions have revealed diagnoses in up to 90 percent of cases when very aggressive diagnostic approaches are taken [10]. Such aggressive approaches are often not warranted in clinical practice, however, given the benign natural history of many of these effusions. (See "Acute pericarditis: Clinical presentation and diagnosis", section on 'Establishing a definite etiology'.)

Causes — Pericardial effusion can develop in patients with virtually any condition that affects the pericardium, including acute pericarditis and a variety of systemic disorders. The development of a pericardial effusion may have important implications for prognosis (as in patients with intrathoracic neoplasm), diagnosis (as in myopericarditis or acute pericarditis), or both (as in dissection of the ascending aorta).

Pericardial effusions can occur as a component of almost any pericardial disorder (table 1), but the majority result from one of the following conditions (see "Etiology of pericardial disease"):

●Acute pericarditis (viral, bacterial, tuberculous, or idiopathic in origin)

●Autoimmune disease

●Post-myocardial infarction or cardiac surgery

●Sharp or blunt chest trauma, including a cardiac diagnostic or interventional procedure

●Malignancy, particularly metastatic spread of noncardiac primary tumors

●Mediastinal radiation

●Renal failure with uremia

●Myxedema

●Aortic dissection extending into the pericardium

●Selected drugs

The frequency of the different causes of pericardial effusion varies in published reports, depending primarily upon geography and the patient population (table 2). Patients with hemorrhagic pericardial effusions have a somewhat different distribution of causes, although the overlap with serous effusions is significant. (See "Etiology of pericardial disease", section on 'Spectrum of clinical presentation'.)

Evaluation — Selected clinical information may be helpful for establishing the etiology of a pericardial effusion. This was illustrated in a review of 322 patients with a moderate or large pericardial effusion [9]. In 60 percent of patients, the cause of the effusion was a known medical condition. In the remaining patients, the cause of the effusion was assessed based upon the following features:

●The size of the effusion.

●The presence or absence of cardiac tamponade.

●Inflammatory signs (defined as two or more of the following features: characteristic chest pain, pericardial friction rub, fever >37°C, and diffuse ST-segment elevation).

The presence or absence of these features suggested, but did not confirm, a specific diagnosis [9]:

●The presence of inflammatory signs was associated with acute idiopathic pericarditis (likelihood ratio 5.4).

●A large effusion without inflammatory signs or cardiac tamponade was associated with chronic idiopathic pericardial effusion (likelihood ratio 20).

●Cardiac tamponade without inflammatory signs was associated with a malignant effusion (likelihood ratio 2.9).

Laboratory tests — If the initial history and physical examination do not suggest a specific diagnosis, extensive laboratory testing seeking an etiology is unlikely to be helpful. In such cases, we limit routine testing to:

●Complete blood count

●Chemistry profile and renal function

●Thyroid function

●Chest radiography

A serum antinuclear antibody (ANA) test should be considered in a young female with an effusion and associated acute pericarditis since, rarely, this can be the initial presentation of systemic lupus erythematosus.

A careful history directed toward the presence of a coexisting rheumatologic disorder should also be obtained. It is important to keep in mind that a positive ANA is a nonspecific finding. In cases where a rheumatologic diagnosis is being considered in a patient with pericarditis and an effusion, a rheumatology consultation should be sought. (See "Pericardial involvement in systemic autoimmune diseases".)

Pericardial fluid analysis and biopsy — Drainage of a pericardial effusion is often performed for therapeutic benefit (ie, in cardiac tamponade). However, pericardial fluid drainage and analysis should be considered for diagnostic purposes in patients without cardiac tamponade if there is significant uncertainty regarding the diagnosis or if knowledge of a particular diagnosis would change the management of the patient (ie, the presence of metastatic malignancy). In addition, pericardial biopsy can be an important part of the diagnostic approach.

The invasive nature of pericardiocentesis and pericardial biopsy must be weighed against two factors: a relatively low diagnostic yield from the procedure, and the clinical relevance of a specific diagnosis, as many low-risk patients can be managed empirically without making a specific diagnosis. The yield of diagnostic pericardiocentesis has varied in different series, but in most, a definitive diagnosis has been made following pericardiocentesis in less than 40 percent of cases [10,11,13]. In a more contemporary series of 269 patients who had undergone pericardiocentesis, an etiology was determined in 74 percent of cases; the most common etiologies were idiopathic in 26 percent, malignant in 25 percent, and iatrogenic in 20 percent [15]. When an etiology for the pericardial effusion was confirmed, malignancy, purulent infection, and tuberculosis were the most frequently identified causes.

We consider pericardial fluid analysis and pericardial biopsy separately since they are frequently helpful, but many patients are successfully managed without either procedure. Our approach is in general agreement with the 2015 European Society of Cardiology guidelines for the diagnosis and management of pericardial disease [5].

We perform pericardial fluid analysis in the following settings:

●In any patient undergoing therapeutic pericardiocentesis for treatment of cardiac tamponade.

●When there is a clinical suspicion of purulent, tuberculous, or neoplastic pericarditis. (See "Purulent pericarditis" and "Tuberculous pericarditis" and "Pericardial disease associated with cancer: Clinical presentation and diagnosis".)

●In patients with moderate-to-large pericardial effusions of unknown etiology that do not respond rapidly to antiinflammatory therapy.

In patients with chronic pericardial effusions, we do not recommend repeated diagnostic pericardiocentesis due to its low yield.

The biochemical, immunologic, cytologic, and bacteriologic characteristics of an effusion can be established by laboratory analysis of the pericardial fluid. In some cases this analysis can also determine the etiology of the effusion [16,17]. Among the most helpful diagnostic studies are:

●Gram stain and bacterial and fungal culture.

●Cytology.

●Acid-fast bacillus (AFB) stain and mycobacterial culture along with adenosine deaminase, interferon-gamma, or lysozyme (for tuberculous pericarditis) [18].

●Polymerase chain reaction (PCR) testing is ordered if a specific organism (eg, Mycobacterium tuberculosis) is suspected.

Parameters such as protein, lactate dehydrogenase (LDH), glucose, red cell count, and white cell count are rarely helpful in establishing an etiology; specifically, Light criteria, used for differentiating transudative versus exudative pleural effusions, do not reliably distinguish exudative from transudative pericardial effusions and should not be applied to pericardial fluid analysis [19,20]. However, a PCR test for specific viruses can be ordered when management may be affected by the results, such as identifying cytomegalovirus (CMV) in a transplant patient, although the yield of PCR remains fairly low in many instances [21]. (See "Etiology of pericardial disease" and "Tuberculous pericarditis" and "Approach to the diagnosis of cytomegalovirus infection".)

If patient characteristics and local expertise favor pericardial drainage via percutaneous pericardiocentesis, analysis is limited to the pericardial fluid. However, whenever surgical drainage is performed, we also recommend pericardial biopsy. In addition, pericardial biopsy should be performed in any patient in whom there is ongoing diagnostic uncertainty as to the etiology if a specific diagnosis would significantly change the management.

Pericardioscopy enables endoscopic inspection and targeted biopsy of the parietal and visceral pericardium [2]. This approach has been used in patients with unexplained pericardial effusions or to diagnose recurrent idiopathic effusion [22-25]. When performed in one of the few centers with a special interest and expertise in using this approach, a specific diagnosis was established in 49 to 65 percent of patients, a value higher than generally obtained by pericardial biopsy performed under fluoroscopic guidance [22-24].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Pericardial disease".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topic (see "Patient education: Cardiac tamponade (The Basics)")

●Beyond the Basics topics (see "Patient education: Pericarditis (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Etiology – Pericardial effusion can develop in patients with virtually any condition that affects the pericardium (table 1), including acute pericarditis and a variety of systemic disorders. The frequency of different causes of pericardial effusion varies in published reports, depending on factors including geography and patient demographics, as well as the aggressiveness with which an underlying diagnosis is sought (table 2).

●Clinical presentation – The presence of pericardial effusion may be suspected from the history, physical examination, ECG, and chest radiograph. However, in the absence of cardiac tamponade, physical signs are not sensitive or specific for pericardial effusion. (See 'Diagnostic approach' above.)

●Diagnosis and evaluation – Once a pericardial effusion is suspected, the diagnostic approach consists of three steps: confirming the presence of a pericardial effusion (generally by echocardiography), assessing its hemodynamic impact (ie, determining if cardiac tamponade is present), and identifying the cause of the pericardial effusion.

•Diagnosis – The presence of pericardial effusion is usually established with echocardiography. (See 'Cardiac imaging' above.)

•Assess the hemodynamic impact – Both clinical and echocardiographic findings can be helpful in assessing the hemodynamic impact of a pericardial effusion. Cardiac tamponade occurs when the intrapericardial pressure from an accumulating pericardial effusion impedes filling of one or both ventricles. (See 'Urgent conditions' above.)

Patients with cardiac tamponade require urgent pericardial fluid drainage, as discussed separately. (See "Cardiac tamponade" and "Pericardial effusion: Approach to management", section on 'Indications for pericardial fluid removal'.)

•Identification of the cause – In some cases, the most likely cause of the pericardial effusion will be clear due to the presence of another illness or systemic disorder known to involve the pericardium. If the cause is not apparent, the routine use of a broad panel of screening laboratory tests is not usually helpful. In such cases, evaluation of the pericardial fluid and pericardium itself may suggest an etiology, particularly if the effusion is large.

Patients with suspected purulent pericarditis require urgent diagnosis and management, including pericardial drainage, as discussed separately. (See "Purulent pericarditis".)