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Health condition

Pleural empyema, infected fluid around the lung - and how it is cleared.

It usually starts as pneumonia that will not settle. Finding it early, draining it well and knowing when to involve a surgeon is what changes the outcome.

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A radiographer guides a patient onto the bed of an advanced 3 Tesla MRI scanner in a London imaging suite

Why trust this guide

  • 01

    Editorial team

    Written by our editorial team from the UK sources listed on each page.

  • 02

    Sourced from guidance

    Checked against the British Thoracic Society Pleural Disease Guideline 2023 and the trials behind it, listed at the end.

  • 03

    Current for 2026

    Reflects modern UK practice including image-guided small-bore drains, intrapleural tPA and DNase, and early surgical referral.

Key facts

Pleural empyema at a glance.

The essentials, in plain English - what it is, why it happens and how it is treated in the UK today.

  • What it is

    Infected fluid - pus, or fluid that is heading that way - trapped in the pleural space between the lung and the chest wall.

  • Usual cause

    A complication of pneumonia. Less often it follows chest surgery or trauma, oesophageal rupture or an infection below the diaphragm.

  • Three stages

    Simple parapneumonic effusion, then complicated parapneumonic effusion, then empyema - the fluid thickens and forms septations as it goes.

  • Who is at risk

    People with diabetes, heavy alcohol use, injecting drug use, weakened immunity, aspiration risk, older age - and children after pneumonia.

  • Key test

    Sampling the fluid. Pus, a pH below 7.2, glucose below 3.4 mmol/L or a positive culture all point to infection needing drainage.

  • Core treatment

    Prompt broad-spectrum antibiotics with anaerobic cover plus chest drainage, with surgery held in reserve for those who do not settle.

Why this guide matters

Pneumonia that will not settle deserves a second look.

Pleural infection is easy to miss early and hard to treat late. The three points below shape everything else on this page.

  • Persistent fever is a signal

    If pneumonia is not improving after a few days of antibiotics, an ultrasound and a sample of any pleural fluid can find infection early.

  • Antibiotics need drainage

    Once fluid is infected, it usually has to be drained. A small-bore drain with the right adjuncts avoids surgery for most people.

  • Early surgical opinion helps

    If there is no clear improvement at around five to seven days, involving a thoracic surgeon sooner shortens illness and hospital stay.

How the diagnosis is made

From a fever that lingers to a clear plan.

The steps a respiratory team will normally follow, in order - so you know what to expect and why.

  1. 01

    Assessing

    Clinical assessment

    Fever that persists despite antibiotics, pleuritic pain and reduced breath sounds over the affected side prompt a closer look.

  2. 02

    Assessing

    Chest X-ray

    Shows fluid as a blunted costophrenic angle or a dense white area - it cannot say whether the fluid is infected.

  3. 03

    Assessing

    Bloods and cultures

    Inflammatory markers, white cell count, kidney function and albumin, plus blood cultures before or alongside antibiotics.

  4. 04

    Confirming

    Thoracic ultrasound

    Shows the size of the collection, any septations and the safest spot to insert a needle or drain.

  5. 05

    Confirming

    Diagnostic pleural aspiration

    A small sample of fluid is checked for pus, pH, glucose and culture. pH under 7.2 usually means a drain is needed.

  6. 06

    Planning

    CT chest with contrast

    Maps loculated pockets, looks at the lung underneath and helps identify a cause such as a blocked airway.

  7. 07

    Planning

    Risk scoring - RAPID

    Kidney function, age, purulence, infection source and albumin combine into a score that helps predict outcome and plan follow-up.

Typical timeline: assessment and fluid sampling within a day or two of suspicion, with treatment started straight away.

Symptoms

What pleural empyema actually feels like.

Often it looks like pneumonia that has stalled. Symptoms build over days to weeks - and some features mean it is time to act quickly.

  • Persistent fever

    A temperature that keeps returning despite a course of antibiotics for pneumonia is the classic warning sign.

  • Pleuritic chest pain

    Sharp pain that catches on breathing in or coughing, usually on one side of the chest.

  • Breathlessness

    Fluid squeezes the lung, so even short walks or stairs can leave you short of breath.

  • Malaise and exhaustion

    A deep, flat tiredness and feeling generally unwell that does not lift as pneumonia should.

  • Weight loss and poor appetite

    Common when the infection has been simmering for weeks - and a reason to check for other causes too.

  • Cough

    Often present from the original pneumonia, with or without sputum. It may ease while the pleural infection persists.

  • Sweats and rigors

    Drenching night sweats or shaking chills reflect a significant ongoing infection.

  • Red flag - signs of sepsis

    Confusion, a racing heart, low blood pressure or very fast breathing need emergency assessment.

Treatment

How pleural empyema is treated in the UK.

Antibiotics and drainage together, intrapleural drugs for thick or loculated fluid, and keyhole surgery for those who do not settle.

  • Broad-spectrum antibiotics

    Started promptly and chosen to cover the usual bacteria including anaerobes. Adjusted once cultures return, and often continued for several weeks.

  • Small-bore chest drain

    A thin tube placed under ultrasound guidance to drain the infected fluid. Usually the first drainage step for pleural infection.

  • Saline flushes

    Regular small flushes of saline through the drain help keep it clear and support drainage of thick fluid.

  • Intrapleural tPA and DNase

    Two drugs given through the drain in loculated or thick collections. They break up septations and thin the pus so it drains.

  • VATS decortication

    Keyhole surgery to clear infected material and free the lung. Considered when infection and a residual collection persist despite drainage.

  • Nutritional support

    Infection and weight loss go together. Dietitian input and supplements help wound healing and recovery of muscle.

  • Chest physiotherapy

    Breathing exercises and early mobilisation help the lung re-expand and reduce the risk of further chest infection.

  • Treating the source

    Managing the cause and the risks - blood sugar, alcohol, aspiration, an obstructed airway or a source below the diaphragm.

What this guide is based on

The sources behind every claim on this page.

UK national guidance and the key trials behind it, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your respiratory physician or GP knows your history and can tell you which parts apply to you. If in doubt, get seen.

  • British Thoracic Society. BTS Pleural Disease Guideline 2023 (Thorax, 2023).

  • Rahman NM et al. Intrapleural use of tissue plasminogen activator and DNase in pleural infection (MIST2). New England Journal of Medicine, 2011.

  • Rahman NM et al. The RAPID score for predicting mortality in pleural infection. Chest, 2014.

  • NICE. Guidance on the diagnosis and management of pneumonia in adults.

Red flags

When pleural infection needs urgent attention.

Pleural infection can become serious quickly. These are the situations that need emergency care or an early specialist opinion.

  • Signs of sepsis

    Confusion, fast heart rate, low blood pressure, cold clammy skin or very fast breathing - call 999 or go to A&E immediately.

  • Respiratory failure

    Severe breathlessness at rest, blue lips or difficulty speaking in full sentences is an emergency needing oxygen and hospital care.

  • No improvement after 5 to 7 days

    Ongoing fever, high inflammatory markers or a persisting collection despite antibiotics and drainage should prompt an early surgical opinion.

  • Fever after chest surgery or trauma

    A new temperature and worsening chest pain in the days or weeks after an operation or injury to the chest needs prompt review.

  • Severe pain after vomiting

    Sudden severe chest pain after forceful vomiting or an oesophageal procedure can signal oesophageal rupture - an emergency.

  • Persistent air leak

    Air bubbling continuously in the drain, or coughing up large volumes of fluid, can indicate a bronchopleural fistula and needs specialist review.

  • Blocked or stopped drain

    A drain that stops draining while fever continues may mean a blocked tube or a pocket of pus it cannot reach.

  • Unwell child after pneumonia

    Fast breathing, persisting fever or refusing to feed after pneumonia in a child warrants same-day paediatric assessment.

  • Weight loss with a persistent effusion

    Unexplained weight loss alongside pleural fluid deserves a search for an underlying cause, including a blocked airway or cancer.

Living with it

A slow recovery, with a clear path back.

Four things that make the biggest difference once the infection is under control - patience, movement, nutrition and follow-up.

A quiet reminder

Prevention is part of recovery.

Keeping vaccinations up to date, stopping smoking, controlling diabetes and cutting back on alcohol all lower the chance of another chest infection.

  1. 01 Recovery

    Expect weeks, not days

    Antibiotics often continue for several weeks and energy returns gradually. Fatigue and some breathlessness can linger while the lung re-expands.

  2. 02 Movement

    Keep moving and breathing deeply

    Short, regular walks and the breathing exercises your physiotherapist teaches help the lung re-expand and protect against another chest infection.

  3. 03 Nutrition

    Feed the recovery

    Protein-rich meals and supplements help rebuild strength after weight loss. Limit alcohol - it slows healing and raises the risk of a repeat infection.

  4. 04 Follow-up

    Attend the review scans

    A repeat chest X-ray and clinic review check the fluid has cleared. Mild pleural thickening can persist and often improves over months.

Frequently asked

Everything we get asked about pleural empyema.

Quick answers on how it differs from an effusion, why drainage matters and when surgery is needed.

  • What is pleural empyema?

    It is a collection of infected fluid or pus in the pleural space - the thin gap between the lung and the chest wall. It usually develops as a complication of pneumonia and needs drainage as well as antibiotics.

  • How is it different from a pleural effusion?

    A pleural effusion is any excess fluid in the pleural space and is often not infected. Empyema is the infected end of the spectrum, identified by sampling the fluid - pus, a low pH, low glucose or a positive culture.

  • Why can antibiotics alone not clear it?

    Infected pleural fluid thickens and forms septations, creating pockets that antibiotics cannot fully reach. Draining the fluid removes the infected material and lets the lung expand, so antibiotics and drainage work together.

  • What are tPA and DNase used for?

    They are drugs given through the chest drain in loculated or thick collections. Tissue plasminogen activator breaks down fibrin septations and DNase thins the pus. Used together they improve drainage and can reduce the need for surgery.

  • When is surgery needed?

    When infection and a residual collection persist despite antibiotics, a good drain and intrapleural treatment - usually judged after around five to seven days. Video-assisted thoracoscopic surgery (VATS) decortication clears the infected material and frees the lung.

  • How long does recovery take?

    Most people improve over several weeks. Drain time varies, antibiotics often continue after discharge, and fatigue can last for weeks or months. Some pleural thickening may remain, usually with few long-term effects.

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