01OverviewDefinition, clinical context and the essential points that orientate the chapter.
Pericardial effusion may accompany inflammation, malignancy, bacterial or tuberculous infection, renal failure, hypothyroidism, heart failure, autoimmune disease, trauma, aortic disease or a recent cardiac procedure. Sometimes the cause remains uncertain after a proportionate investigation.
Management is determined by physiology, symptoms, cause and trajectory rather than a single size threshold. Comparison with previous imaging often distinguishes a tolerated chronic collection from a rapidly evolving emergency.
When an effusion accompanies active pericarditis, assess fluid physiology separately and use the acute or recurrent pericarditis regimen appropriate to the inflammatory phenotype; isolated fluid has no automatic anti-inflammatory indication.
Key points
- An effusion is a finding, not a diagnosis. Establish the clinical context, likely cause, echo size, haemodynamic effect and whether the volume is stable, enlarging or recurring.
- Slow accumulation may permit a very large effusion without shock; rapid bleeding can produce tamponade with a much smaller echo measurement.
- TTE should describe distribution, end-diastolic separation, chamber interaction, respiratory Doppler changes, IVC response, ventricular function and comparison with prior studies.
- Tamponade is a clinical-haemodynamic diagnosis. Tachycardia, raised JVP, pulsus paradoxus and impaired perfusion matter more than the presence or absence of the complete Beck triad.
- Drain urgently for haemodynamic compromise. Drain or obtain tissue for suspected purulent, tuberculous or malignant disease when the result and source control will alter treatment, even if classic tamponade is absent.
- A symptomatic, enlarging, recurrent or loculated effusion needs specialist review for catheter drainage, surgical window, biopsy or other cause-directed intervention.
- Isolated non-inflammatory fluid should not be treated automatically with aspirin, an NSAID, colchicine or corticosteroid. Use the dedicated Acute pericarditis and Recurrent pericarditis chapters when active inflammatory pericarditis is present.
- After drainage, track output and re-accumulation, send a complete targeted specimen set and document who will act on culture, cytology and biopsy results.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Inflammatory pericardial disease
Viral or idiopathic pericarditis, autoimmune disease and inflammation after myocardial injury can increase pericardial fluid production. Pain, inflammatory markers or pericardial enhancement support an active inflammatory phenotype.
Malignancy or infection
Cancer can infiltrate or obstruct pericardial drainage, while bacterial or tuberculous infection produces inflammatory exudate. Recurrent haemorrhagic fluid, systemic illness or immunosuppression increases concern.
Systemic fluid disorders
Renal failure, hypothyroidism and heart failure can permit gradual fluid accumulation through altered permeability, impaired drainage or raised venous pressure. These effusions may become large before symptoms appear.
Bleeding and procedural injury
Cardiac procedures, trauma, aortic disease or myocardial rupture may cause haemopericardium. Rapid bleeding raises intrapericardial pressure before a large fluid volume can accumulate.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Fluid accumulates
Inflammatory secretion, impaired lymphatic drainage or bleeding causes fluid to collect between the visceral and parietal pericardial layers faster than it can be removed.
- 2Pressure depends on speed
A slowly stretching pericardium can accommodate considerable fluid, whereas rapid accumulation produces a steep pressure rise with a much smaller volume. Size alone therefore does not define danger.
- 3Diastolic filling becomes restricted
When intrapericardial pressure approaches chamber filling pressure, right-atrial collapse may occur during systole and right-ventricular collapse in early diastole. Ventricular interaction becomes exaggerated with respiration.
- 4Tamponade causes obstructive shock
Restricted cardiac filling lowers stroke volume and cardiac output while systemic venous pressure rises. Compensatory tachycardia may eventually fail, producing hypotension, organ hypoperfusion and cardiac arrest.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
An asymptomatic collection may be found on echo or CT. Review earlier imaging, systemic symptoms, cancer history, renal and thyroid disease, inflammatory features and recent procedures before deciding that observation is sufficient.
Progressive dyspnoea, tachycardia, raised JVP, narrow pulse pressure, pulsus paradoxus, cool peripheries, oliguria, confusion or rising lactate indicates impaired filling and falling output.
Collapse after an invasive cardiac procedure, penetrating or blunt trauma, suspected type A aortic dissection or myocardial rupture may occur before the effusion appears large. Clot and loculation can make standard echo views misleading.
Fever, toxicity, bacteraemia, pneumonia or empyema, recent thoracic surgery, immunosuppression or a neutrophilic fluid appearance raises concern for bacterial infection and demands urgent drainage and antimicrobial source control.
Known cancer, weight loss, mediastinal disease, recurrent haemorrhagic fluid or unexplained large effusion should prompt cytology and oncology-linked assessment; a negative first sample does not always exclude malignancy.
Pleuritic positional pain, a rub, widespread ST or PR change, raised inflammatory markers or pericardial enhancement suggests active pericarditis. Confirm the phenotype and use the dedicated pericarditis chapter rather than treating fluid alone.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Transthoracic echocardiographyFirst step - Why
- Confirm fluid, measure the largest end-diastolic separation in standard views, define circumferential versus loculated distribution and assess haemodynamic effects.
- Interpretation and limitations
- Report small, moderate or large size with the actual measurement and comparison date. Right-atrial systolic collapse, right-ventricular early-diastolic collapse, marked respiratory inflow variation and a plethoric IVC support tamponade but must be integrated with the patient's circulation.
- 02
Serial echo comparison - Why
- Establish whether the collection is new, stable, enlarging, recurring after drainage or becoming loculated.
- Interpretation and limitations
- An increasing collection or new chamber interaction shortens the follow-up interval and may change an observational plan to drainage or surgical review.
- 03
ECG and continuous monitoring when unwell - Why
- Identify low voltage, electrical alternans, pericarditic change, ischaemia and peri-arrest rhythm.
- Interpretation and limitations
- A normal ECG does not exclude a clinically important effusion. Electrical alternans supports a large mobile collection but is not required for tamponade.
- 04
Baseline and cause-directed blood tests - Why
- Use FBC, CRP or ESR, U&E and eGFR, LFT, clotting, thyroid tests, blood cultures and autoimmune or infection tests according to presentation.
- Interpretation and limitations
- Testing should answer a clinical question. Obtain blood cultures before antibiotics when this causes no harmful delay, but do not postpone treatment of sepsis or purulent disease.
- 05
CT or CMR - Why
- Define loculation, clot, pericardial thickening or mass, extracardiac malignancy, inflammation and a safe procedural strategy when the patient is stable.
- Interpretation and limitations
- Cross-sectional imaging adds anatomy and tissue context but must not delay decompression in shock. CMR evidence of inflammation redirects drug treatment to the pericarditis pathway.
- 06
Pericardial fluid analysis - Why
- Send appearance, cell count and differential, protein and other locally agreed chemistry, Gram stain and bacterial culture, cytology and targeted TB, fungal or molecular tests according to risk.
- Interpretation and limitations
- Use the whole clinical and pathological picture; one negative culture or cytology result may be non-diagnostic. Record which team will review every pending result.
- 07
Pericardial or surgical tissue - Why
- Obtain histology and microbiology when fluid is non-diagnostic and malignancy, TB, persistent infection or another infiltrative process remains likely.
- Interpretation and limitations
- Choose biopsy when the expected diagnostic value will alter treatment, often during a required surgical drainage procedure rather than as an isolated low-yield intervention.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Pleural effusion
Pleural fluid causes breathlessness and reduced breath sounds but lies outside the pericardial sac. Thoracic ultrasound or echocardiography identifies its anatomical relation to the heart.
High-risk pulmonary embolism
Pulmonary embolism can produce raised venous pressure, tachycardia and obstructive shock. Right-ventricular dilatation, thromboembolic clues and absent pericardial compression favour embolism.
Cardiogenic shock
Severe ventricular failure causes low output and pulmonary congestion but usually shows primary pump dysfunction rather than chamber compression. Echocardiography differentiates the haemodynamic mechanism.
Constrictive pericarditis
Constrictive disease causes chronic impaired filling, raised JVP and ventricular interdependence through a rigid pericardium. Imaging may show thickening or calcification without a haemodynamically important effusion.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01AssessDefine cause, physiology and trajectoryFirst stepA new or previously documented pericardial effusion is identified.+
- 1Assess symptoms, pulse, blood pressure, JVP, perfusion, pulsus paradoxus when appropriate and any precipitating procedure, trauma, infection, renal failure, thyroid disease, autoimmune disease or cancer.
- 2Obtain TTE and compare with every available prior study. Document distribution, measured size, chamber interaction, respiratory Doppler findings, IVC and ventricular function.
- 3EscalationUse baseline and cause-directed tests rather than an indiscriminate panel. Escalate immediately if the collection is increasing rapidly or haemodynamic findings are evolving.
- 4For a stable, asymptomatic collection without a high-risk cause or tamponade physiology, agree a cause-based surveillance interval and explicit deterioration advice.
02EmergencyTamponade or threatened circulationShock, worsening perfusion or progressive symptoms with clinical and echo evidence of pericardial compression.+
- 1DefinitiveCall a drainage-capable cardiology and critical-care team, monitor continuously, obtain vascular access and use focused echo without delaying definitive treatment.
- 2Proceed to urgent image-guided pericardiocentesis with catheter drainage when anatomically appropriate. Choose surgical drainage for trauma, suspected aortic rupture, clotted postoperative blood, purulence, inaccessible or heavily loculated fluid, or when operative source control is required.
- 3Avoid routine diuresis, vasodilation and avoidable positive-pressure ventilation before decompression because reducing venous return can precipitate collapse; any temporary haemodynamic bridge must not replace drainage.
- 4Use the dedicated Cardiac tamponade chapter for peri-arrest detail and the special precautions around aortic dissection or traumatic haemopericardium.
03Drain or sampleSelect intervention for a stable effusionThe patient is not in shock but the cause, symptoms, size, trajectory or recurrence may justify intervention.+
- 1Arrange diagnostic drainage or tissue when purulent, tuberculous or malignant disease is suspected and the result will direct treatment; do not wait for classic tamponade when source control is needed.
- 2Consider therapeutic drainage for a persistent symptomatic large collection, progressive enlargement or clinically important recurrence after balancing procedural access and cause.
- 3Choose an image-guided percutaneous catheter when there is a safe fluid window; choose a surgical window or biopsy when fluid is loculated, recurs repeatedly, tissue is required or percutaneous drainage will not achieve source control.
- 4Before the procedure, define the specimen plan, anticoagulation and bleeding issues, likely access and post-procedure monitoring. Life-saving drainage should not be withheld solely because correction of coagulopathy is incomplete.
04InfectionPurulent effusionSepsis, positive blood culture, adjacent infection or fluid findings suggest bacterial pericardial infection.+
- 1Obtain blood and pericardial cultures without delaying treatment, start immediate intravenous antimicrobial therapy using microbiology advice and achieve complete drainage.
- 2Involve cardiothoracic surgery early because thick pus, septations and loculation frequently prevent adequate needle drainage and may require operative washout or window.
- 3Search for and control the source, including pneumonia, empyema, endocarditis, thoracic surgery or haematogenous infection, and narrow therapy to microbiology when available.
- 4Repeat imaging and inflammatory assessment to confirm resolution and identify constrictive evolution or re-accumulation.
05Cancer or recurrencePrevent repeated symptomatic accumulationMalignant, recurrent or repeatedly symptomatic effusion after initial drainage.+
- 1Send adequate-volume cytology and coordinate pathology, oncology and cardiology review; pursue tissue or extracardiac biopsy when the first sample is non-diagnostic and the result would alter cancer care.
- 2Use catheter drainage to monitor output and confirm lung and cardiac recovery. Discuss a surgical or percutaneous window, indwelling strategy or other local treatment when repeated accumulation is likely.
- 3Treat the underlying cancer or systemic cause when feasible and include prognosis, symptom burden and patient preference in the intervention plan.
- 4After any drainage, document a repeat-echo plan, drain-removal criteria, warning symptoms and named ownership of cytology, culture and recurrence follow-up.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Cardiac tamponade
Rising pericardial pressure prevents adequate chamber filling and produces obstructive shock. Deterioration can be rapid, particularly after bleeding, trauma or an invasive cardiac procedure.
Recurrent or loculated effusion
Malignant, purulent or postoperative fluid may reaccumulate or become divided by adhesions. Loculation complicates imaging and drainage and may require a surgical window or tissue sampling.
Constrictive physiology
Prolonged or intense pericardial inflammation can heal with fibrosis and impaired expansion. Persistent venous congestion may remain even after the free fluid has been drained.
Purulent sepsis
An infected collection can seed the bloodstream and become loculated. Antimicrobials may not provide adequate source control without complete drainage and early specialist surgical involvement.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- For any inpatient or unstable patient, monitor ECG, blood pressure, oxygen saturation, mental state, urine output and peripheral perfusion and reassess immediately after a clinical change.
- Repeat TTE urgently for new hypotension, tachycardia, raised JVP, worsening breathlessness or low-output features; do not rely on the previous fluid measurement.
- For conservatively managed effusion, set the next echo from cause, measured size and trajectory rather than using one interval for every patient.
- After pericardiocentesis, chart drain output and character, observe the access site and haemoglobin, and repeat imaging if output stops unexpectedly or symptoms recur.
- Watch for re-accumulation, bleeding, pneumothorax, infection and pericardial-decompression syndrome after drainage.
- Track every microbiology, cytology and tissue result to completion and record the clinician or team responsible for acting on it.
- In malignant or recurrent disease, align follow-up with oncology or the relevant specialty and revisit the balance between repeat procedures, durable drainage and symptom-focused care.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Trajectory beats a snapshot
A dated comparison with earlier imaging often contributes more than the label small, moderate or large because it shows whether the pressure-volume curve is being approached rapidly.
Tamponade is physiology
Echo signs support impaired filling, but treatment is driven by the patient's circulation. Positive-pressure ventilation, pulmonary hypertension, hypovolaemia and postoperative loculation can alter the classic pattern.
Sampling starts before the needle
The likely diagnoses determine tube types, volumes and laboratory destinations. A planned specimen set avoids losing the only opportunity for microbiology or cytology.
Purulent fluid needs source control
Antibiotics alone may not penetrate and clear a loculated infected collection; complete drainage and early surgical input are central treatment components.
A negative cytology result is contextual
Diagnostic sensitivity depends on tumour type, sample quality and burden. Persisting clinical suspicion may justify repeat fluid, pericardial tissue or biopsy of a safer extracardiac site.
Inflammation is a separate treatment decision
Fluid without evidence of active pericardial inflammation has no automatic anti-inflammatory drug target; cause and haemodynamics remain the treatment priorities.
11Common pitfallsFrequent interpretation and management errors.
- 01
Calling an effusion stable without comparing it with prior imaging or specifying its measured size and date.
- 02
Equating a small measurement with safety after a procedure or trauma, or equating a large chronic collection with tamponade in the absence of haemodynamic evidence.
- 03
Waiting for hypotension or the complete Beck triad before escalating evolving tamponade.
- 04
Sending an unstable patient to CT when immediate focused echo and drainage or surgery are required.
- 05
Performing repeated aspiration without a recurrence strategy for malignant or loculated disease.
- 06
Starting an anti-inflammatory pericarditis regimen solely because fluid is present despite no inflammatory phenotype.
- 07
Failing to assign ownership of cytology, culture or biopsy results after discharge or transfer.