Pericardial fluid: acceptable levels and what the finding means

Pericardial effusion is an excess of fluid between the visceral and parietal layers of the pericardium. Normally, this "lubricating" space in a healthy person contains approximately 15-50 ml of serous fluid; it reduces friction and helps the heart move freely. Any volume above the physiological limit is considered an effusion and requires an assessment of the context: acuity, causes, symptoms, and hemodynamic significance. [1]

The key question when detecting an effusion is whether there is a threat to blood flow (tamponade) and how quickly the volume has accumulated. A small, slowly developing effusion in an asymptomatic patient is often harmless; conversely, even a moderate volume accumulated over hours can cause cardiac compression and a drop in blood pressure. Therefore, the rate of accumulation is more important than the liters and millimeters themselves. [2]

The diagnostic "skeleton" is simple: echocardiography as a first-line method confirms the presence of fluid, evaluates its thickness in diastole, distribution and signs of tamponade; then, according to indications, laboratory diagnostics, computed tomography or magnetic resonance imaging are carried out to clarify the causes, especially if a tumor, tuberculosis, trauma or complicated purulent process is suspected. [3]

Management is always two-step: (1) stabilization (recognize and, if necessary, urgently drain the threat of tamponade), (2) search for and treatment of the cause (viral/autoimmune pericarditis, uremia, hypothyroidism, neoplasm, tuberculosis, post-procedural complications, etc.). It is the cause that will determine the prognosis and long-term tactics, and not the fact that “there is fluid” itself. [4]

Epidemiology

In developed countries, up to half of moderate-to-large effusions remain idiopathic (often viral or immune in nature) despite careful examination; other common causes include cancer (approximately 10-25%), infections (including tuberculosis - up to 60% in endemic regions), iatrogenic injuries, and connective tissue diseases. A significant proportion of effusions are detected incidentally during echocardiography/X-rays performed for other reasons. [5]

In patients with chronic kidney disease, uremic pericarditis with effusion is possible; the first treatment here is intensification of dialysis, and only if there is no effect or signs of tamponade is drainage indicated. According to modern reviews, with intensification of dialysis over 7-14 days, some effusions regress without invasive interventions. [6]

Malignant pericardial effusions are common in patients with lung and breast tumors, lymphomas, melanoma, and metastatic processes. This group has a high risk of recurrence after a single puncture; repeat interventions and pericardial windows reduce the recurrence rate, and survival is largely determined by the oncology. [7]

Postprocedural and postoperative effusions (following electrode implantation, catheterization, and cardiac surgery) are distinguished separately. They are often transient, but in the case of perforations, they can quickly lead to tamponade. Therefore, in patients recently operated/interventionally treated, the threshold for ultrasound monitoring is low. [8]

Reasons

Classic infectious and inflammatory causes include viral (often idiopathic), bacterial (including purulent), tuberculous, and fungal infections in immunocompromised individuals. Tuberculosis is characterized by a subacute course, fever, high protein levels, and lymphocytosis in the fluid; diagnosis is confirmed by microbiology/PCR and clinical and radiological evaluation. [9]

Non-infectious causes: autoimmune diseases (SLE, rheumatoid arthritis, systemic vasculitis), uremia in renal failure, hypothyroidism, radiation therapy to the mediastinum, drug effects (e.g., hydralazine, isoniazid - less common). Each of these has its own markers and "keys" to treatment. [10]

Malignant effusions are caused by pericardial involvement by tumor cells, outflow obliteration, and/or increased vascular permeability. Cytology/biopsy, contrast imaging, and early contact with oncologists are essential: systemic antitumor therapy ultimately determines the sustainability of the effect. [11]

Trauma and iatrogenic injuries (perforations during catheterization, implantation of electrodes, after ablations, cardiac surgeries) can cause hemopericardium with rapid development of tamponade - this is a separate channel of “red flags” where minutes matter. [12]

Risk factors

Risk factors for "harmful" (large, recurrent, or tamponade-threatening) effusions largely overlap with predictors of poor outcome in pericarditis: high fever, subacute course, large effusion, signs of tamponade, lack of response to nonsteroidal anti-inflammatory drugs within a week, immunosuppression/trauma/anticoagulation. The presence of even one of these signs increases the risk of complications and requires inpatient observation. [13]

Risk factors for recurrence include malignancy, tuberculosis, uremia, prolonged immunosuppression, and a pronounced chronic inflammatory background. In patients with chronic renal failure, the key risk modifier is the adequacy of dialysis; in oncology, it is the tumor's sensitivity to systemic therapy. [14]

After cardiac procedures, risk factors for perforations and hemopericardium include antithrombotic therapy, osteoporosis/fragile tissue, complex anatomy, and aggressive instrumentation. Clinics typically have protocols for early postoperative ultrasound to detect dangerous effusions. [15]

Patients with hypothyroidism, CKD, diabetes, and the elderly are more likely to have asymptomatic chronic effusions that are discovered incidentally. Context and assessment of dynamics are important here, rather than a single millimeter reading. [16]

Risk factors for the development of pathology include pregnancy and old age.

The most common causes of pericardial inflammation ( pericarditis ) are tuberculosis and rheumatic diseases. This is an infectious-allergic reaction that results in the formation of a large amount of exudate.

Risk factors in this case can be considered:

• bacterial, viral and fungal diseases: scarlet fever, acute respiratory viral infections, HIV, pneumonia, pleurisy, endocarditis, candidiasis, etc.,
• the presence of parasites in the body ( echinococcal infection, toxoplasmosis, etc.),
• allergic pathologies, including food and drug allergies,
• autoimmune diseases ( rheumatoid arthritis, lupus erythematosus, systemic scleroderma, dermatomyositis, etc.),
• autoimmune processes ( rheumatic fever, etc.),
• chronic heart failure,
• inflammatory diseases of the cardiac membranes ( myocarditis, endocarditis),
• any heart injuries (penetrating and non-penetrating),
• cancer and radiation therapy,
• congenital and acquired pathologies of the development of the pericardium (the presence of cysts and diverticula in it),
• hemodynamic disturbance, edema syndrome,
• diseases of the endocrine system and metabolic disorders ( obesity of the heart, glucose metabolism disorder and diabetes mellitus, hypothyroidism ).

As we have already mentioned, fluid in the pericardium can accumulate as a result of stab wounds to the heart, but the same situation can also be observed after surgery on the organ, as a result of a postoperative complication (inflammation).

Myocardial infarction is a unique form of trauma to the heart, which can also involve inflammatory complications and lead to increased fluid levels in the pericardial sac. The same can be said about ischemic (necrotic) changes in the cardiac myocardium.

If you look closely, you'll see many similarities in the causes of pericarditis and hydropericardium. In theory, the latter condition is a type of non-infectious pericarditis, since congestion in the pericardium inevitably causes inflammatory pathological processes within it.

Pathogenesis

The pericardium is a thin sac containing a small amount of fluid. When production increases (due to inflammation, swelling) or resorption decreases (due to uremia, hypothyroidism), effusion forms. Hemodynamic consequences depend on the rate of accumulation and the distensibility of the pericardium: rapid bleeding of even 150-250 ml can cause tamponade, while slow accumulation of a liter or more is sometimes tolerated for a time without collapse. [17]

Cardiac tamponade is the ultimate point: intrapericardial pressure exceeds the filling pressure of the chambers, primarily the right, leading to collapse of the right atrium and ventricle during diastole, limitation of cardiac output, and shock. Echo signs: diastolic collapse of the right ventricle/systolic collapse of the right atrium, dilated non-collapsing inferior vena cava, respiratory variations in transvalvular flow. [18]

Inflammatory effusion is accompanied by increased protein and cell counts, sometimes with fibrin and septa (loculations). Malignant effusions are often hemorrhagic, with positive cytology; uremic effusions are serous-fibrinous and often regress with increased dialysis. These characteristics help guide treatment. [19]

In chronic cases, effusion can lead to thickening and adhesion of the pericardial layers and the formation of constriction (compressive pericarditis) - another reason for long-term observation after large effusions and purulent/tuberculous forms. [20]

Symptoms

The presentation ranges from a complete absence of complaints to shock. The most common symptoms are shortness of breath, fatigue, a feeling of pressure/heaviness in the chest, intolerance of lying down, and sometimes a dry cough, hiccups, and dysphagia due to compression of adjacent structures. Fever and pleuritic pain may occur with inflammation. [21]

Physical examination may be normal with moderate effusions. With large effusions, muffled tones, jugular vein distension, and a paradoxical pulse are observed; with tamponade, signs of shock are present. An ECG with large effusions may show low voltage and electrical alternans. [22]

Renal patients often have minimal complaints despite significant volumes, so the uremic group is monitored proactively. In cancer patients, symptoms often worsen subacutely, and recurrence of effusion after a single puncture is not uncommon. [23]

There are always “red flags” that raise alarm: increasing shortness of breath at rest, dizziness/fainting, hypotension, severe weakness, “empty” jugular veins without respiratory fluctuations - these are reasons for an emergency echo and, possibly, immediate drainage. [24]

Table 1. Tamponade "Red Flags"

Sign	What does it mean?	Action
Diastolic collapse of the right ventricle, systolic collapse of the right atrium	High probability of tamponade	Immediate decompression
Non-falling IVC (>20 mm)	High intrapericardial pressure	Urgent decision on drainage
Pulsus paradoxus, hypotension, dyspnea at rest	Hemodynamic compromise	Resuscitation algorithm + drainage
Electrical alternans on ECG	Large, movable "heart-swing"	Do not delay Echo/treatment

Forms and stages

By time: acute (hours-days), subacute (weeks), chronic (more than 3 months). By size (echo, diastolic "echo-free" gap): small <10 mm, moderate 10-20 mm, large >20 mm. By distribution: circular or localized. By composition: transudate, exudate, hemorrhagic. This classification helps both assess risks and plan tactics. [25]

By etiology, the following are distinguished: inflammatory (viral/bacterial/tuberculous), tumor, uremic, metabolic (hypothyroidism), post-traumatic/iatrogenic, post-operative. Different causes require different diagnostic kits and pace of intervention. [26]

Special conditions: purulent pericarditis (rare, but extremely dangerous, urgent surgical drainage and antibiotics are indicated), malignant recurrent effusion (often requires long-term drainage tactics/“window” + systemic oncotherapy), uremic (priority is dialysis). [27]

In long-term chronic effusions without inflammation, constriction after resorption is possible - therefore, large and persistent effusions are monitored more closely, even if they are initially asymptomatic. [28]

Table 2. How to read the "size" of effusion by Echo

Criterion	Small	Moderate	Large
Diastolic gap (mm)	<10	10-20	>20
Common symptoms	Often no	Shortness of breath on exertion	Shortness of breath at rest, compression
Risk of tamponade	Short	Average	High
Surveillance tactics	Without frequent monitoring	Control according to plan	Low drainage threshold

Complications and consequences

The main complication is cardiac tamponade, leading to shock and risk of death without immediate drainage. The more rapid the accumulation and the less distensible the pericardium (after inflammation/radiation therapy), the higher the risk of tamponade at smaller volumes. [29]

Long-term risks include recurrences (especially in malignant and tuberculous cases) and constriction after purulent/tuberculous episodes. For cancer patients, frequent recurrent effusions worsen quality of life and require a long-term drainage strategy. [30]

In uremic pericarditis, delayed drainage in the presence of ineffective dialysis increases the risk of infections and hemodynamic complications; however, excessively early invasiveness is also unnecessary if the effusion is stable and there is a chance of regression with adequate dialysis. The balance is determined by the nephrocardiology team. [31]

In postoperative/iatrogenic hemopericardium, complications are determined by the rate of blood loss and coagulopathy; readiness for emergency pericardiocentesis/surgery is important. [32]

Table 3. Common complications and what to do about them

Complication	Context	Tactics
Tamponade	Any rapid accumulation	Immediate drainage
Recurrence of effusion	Malignant, TB, immune	Long-term drainage/window + etiotropy
Constriction	Purulent/TB, chronic	Observation, if confirmed - pericardiectomy
Catheter infection	Long-term drainage	Strict asepsis, replacement/short lead times

Diagnostics

Echocardiography is the first-line test: it confirms the effusion, its size/location, and signs of tamponade, and assesses associated dysfunction. It is useful to document images and sizes in different windows to compare dynamics. Important: hemodynamics depend on the rate of accumulation, not just on the "slit thickness." [33]

CT/MRI are the "second level" for complex anatomy, locations, thick/calcified pericardium, suspected tumor/TB, and when mapping adjacent structures is necessary preoperatively. MRI adds tissue characterization of the pericardium and myocardium, while CT provides information on the relationship with the pleura/mediastinum and volumetric planning. [34]

Laboratory: complete blood count, CRP/ESR, biochemistry (creatinine, liver), TSH (hypothyroidism!), troponin (myopericarditis), coagulogram; if indicated - tuberculosis tests, autoantibodies, tumor markers according to context. If drainage - pericardial fluid analysis (cells, protein, LDH, glucose, culture, PCR/cytology). [35]

When to drain for "diagnosis"? If a bacterial/purulent process, neoplasia, and tamponade are suspected, this is a direct recommendation; in chronic large (>20 mm) idiopathic effusions, pericardiocentesis/drainage can also be considered. [36]

Table 4. Diagnostic route

Step	Tool	Target
1	Echocardiography	Fact, size, tamponade
2	Basic tests	Inflammation, kidneys/thyroid, myocardium
3	CT/MRI (as indicated)	Anatomy, tumor/TB, pericardial thickness
4	Drainage and fluid analysis (as indicated)	Etiology and therapeutic decompression

Differential diagnosis

Not all dyspnea and hypotension with an enlarged cardiac shadow are pericardial effusions: they are differentiated from pleural effusions, massive pulmonary embolism, heart failure with chamber dilation, and acute aortic dissection (which can cause hemopericardium). Echo quickly establishes the correct diagnosis. [37]

Chest pain syndrome differentiates pericarditis (pleuritic pain + friction rub) from myocardial ischemia; troponins and ECG are helpful here, but changes and a moderate increase in troponin (myopericarditis) are also possible with pericarditis. [38]

Large effusions with low voltage and electrical alternans must be distinguished from electrolyte and endocrine causes of low voltage. Again, context is crucial. [39]

In case of fever and subacute course with weight loss, think about tuberculosis and tumor; here the shift is towards early drainage and targeted verification. [40]

Table 5. What can “imitate” effusion/tamponade

State	What is similar?	How to distinguish
Pleural effusion	Shortness of breath, shadow on x-ray	Echo/ultrasound of the pleura, CT
LE (TELA)	Shortness of breath, tachycardia, hypotension	CT angio, echo signs of RV overload without fluid
Aortic dissection	Pain, shock	CT angio of the aorta, hemopericardium
Systolic heart failure	Cardiomegaly, shortness of breath	Echo: dilation, but no fluid

Treatment

1) Emergency care and drainage. If clinical and echocardiographic signs of tamponade are present, immediate ultrasound/X-ray-guided pericardiocentesis with drainage is performed. In cases of purulent pericarditis and complex locations, a surgical window/pericardiectomy is most often indicated. The choice of approach and anesthesia is determined by the patient's condition and the center's experience. [41]

2) Empirical anti-inflammatory therapy for pericarditis. For inflammatory (non-bacterial) effusions, the basis is NSAIDs in adequate doses with gradual withdrawal based on symptoms and CRP, plus colchicine (usually 0.5-1 mg/day adjusted for weight and tolerability) for 3 months during the first episode and up to 6-12 months during relapses: it halves the risk of recurrence. Glucocorticoids - only if indicated (autoimmune cause, intolerance to NSAIDs/colchicine). [42]

3) Etiotropic tactics.

• Uremic effusion: intensification of dialysis (daily/6 times a week for 4 hours for 7-14 days) is the first line; if ineffective or threatened, drainage is recommended. [43]
• Tuberculous/purulent: antibacterial/anti-tuberculosis therapy + surgical drainage if indicated (thick pus, coagulated locules). [44]
• Malignant: systemic antitumor therapy + drainage. A single puncture often results in recurrence; extended drainage or a pericardial window reduces reaccumulation with comparable early mortality. Intrapericardial agents are discussed in individual cases, but systemic tumor treatment is the standard. [45]

4) Long-term management and prevention of chronicity. The catheter is left in place for several days until drainage is reduced; strict aseptic technique is observed. Echo and CRP monitoring helps adjust the timing of NSAID/colchicine discontinuation. In cases of chronic, large idiopathic effusions, planned drainage/window placement may be considered to prevent late tamponade. [46]

Table 6. Where is pericardiocentesis and where is the “window”?

Scenario	Pericardiocentesis (plus drainage)	Surgical "window"
Tamponade, circular effusion	Fast, ultrasound-guided - the method of choice	Reserve if anatomy is complex/locules
Purulent pericarditis	Not always sufficient	Preferred: flushing/debridement
Malignant recurrence	Effective, but relapse rates are higher	Lower relapse rate, comparable early mortality
Chronic large effusion >3 months	Consider	Consider (the effect lasts longer)

Table 7. Anti-inflammatory therapy for pericarditis with effusion (guidelines)

Preparation	Dose (adult)*	Duration	Comments
Ibuprofen	600-800 mg 3 times a day	1-2 weeks with taper according to SRB	Alternatives: aspirin, naproxen
Colchicine	0.5 mg 1-2 times a day	3 months (first episode); 6-12 months (relapse)	Reduces the risk of relapse by approximately 2 times
GKS	Individually	Briefly on the indications	Risk of relapse is higher; avoid first line
IL-1 inhibitors	According to the diagrams	Resistant relapses	In specialized centers
*Doses and regimens are selected by a doctor, taking into account weight, kidneys/liver, and concomitant conditions. [47]

Table 8. “Norms” and gradations: what is considered acceptable

Parameter	Norm	The threshold of "effusion"	Comment
Pericardial fluid volume	≈15-50 ml	>50 ml (clinically significant)	Physiological lubrication
Echo thickness of the diastolic gap	-	≥ some clearance	Classification: <10 / 10-20 / >20 mm
IVC on Echo	Diameter <20 mm, inhalation - collapse	>20 mm, collapse <50%	Sign of high pressure in the pericardium
ECG voltage	Normal	Low/alternance	For large effusions

Prevention

Primary prevention of pericardial effusion as such does not have a specific "pill"; the goal is to control the causes: vaccination and hygiene to reduce infections, thyroid control, careful anticoagulation and invasive procedures, adequate management of autoimmune diseases, and timely screening and treatment of tuberculosis in risk groups. In patients with CKD, dialysis should be optimized to prevent uremic pericarditis. [48]

Secondary prevention of pericarditis recurrence includes colchicine in addition to NSAIDs, cautious and short-term use of glucocorticoids (only when indicated), treatment of triggers (infections, stress), and a monitoring plan with follow-up echocardiography. For cancer patients, close collaboration with oncologists is essential: systemic therapy reduces the risk of recurrent fluid accumulation better than any one-time treatment. [49]

Forecast

The prognosis is determined by the cause and the presence of complications. Small idiopathic effusions without inflammation or symptoms are usually benign and do not require frequent visits. Inflammatory forms, with proper treatment, usually resolve without sequelae; the risk of relapse is significantly reduced with the inclusion of colchicine. [50]

Worse short-term outcomes are associated with tamponade, purulent and tuberculous processes, and malignant effusions. In oncology, outcomes are determined by tumor sensitivity; surgical "window" reduces fluid recurrence but does not change the prognosis of the disease itself. In uremic patients, adequate dialysis improves the prognosis without the need for ongoing invasive interventions. [51]

FAQ

• How much fluid is "normal" in the pericardium?

Typically 15-50 ml. Anything above that, seen on Echo as an “echo-free” gap, is an effusion that requires contextual assessment. [52]

• Is a small asymptomatic effusion dangerous?

More often than not, no. The danger depends on the rate of accumulation and signs of tamponade. Small, asymptomatic effusions are usually observed. [53]

• When is it necessary to puncture the pericardium?

In case of tamponade, suspicion of a bacterial/purulent or malignant process, as well as in case of chronic large (>20 mm) idiopathic effusion. [54]

• Does colchicine help with effusion?

For pericardial effusions, yes: colchicine as part of therapy reduces the risk of relapse and protracted progression. For tumor/uremic effusions, other measures are needed. [55]

• What is better for tumor effusion - puncture or "window"?

Both tactics are comparable in early survival, but the pericardial window has fewer recurrences; the choice depends on the condition, anatomy and oncotherapy plans. [56]