Dr Ken Goh Junyang
Consultant, Department of Respiratory and Critical Care Medicine, Singapore General Hospital

Pleural infection with its intricate clinical presentation often makes diagnosis complex. Increased awareness and a high degree of suspicion in the primary care setting are key to early recognition and treatment. This is vital with local mortality rates of between 4-12% with figures expected to rise with the increasingly elderly population.

INTRODUCTION

What it is

Pleural infection, commonly referred to as complicated parapneumonic effusion or empyema, occurs when there is bacterial entry and replication in the pleural space.

Despite advances in treatment such as closed tube drainage, surgery and intrapleural therapy, the overall mortality rate is reported to be 10-20%, with local mortality rates between 4-12%. The incidence of pleural infection continues to rise worldwide, particularly in the elderly population, where it is associated with the highest mortality. It therefore is a condition associated with significant healthcare burden, and one where early recognition and treatment are important to reduce morbidity and mortality.

Approximately 20-50% of patients with pneumoniahave an associated pleural effusion, of whom approximately 5-10% progress to pleural infection. However, while the term parapneumonic effusion seem to suggest an evolution from pneumonia to pleural infection, we now know that about a third of pleural infection cases have no associated pneumonic illness on radiological assessment.

PRESENTATION

Common presenting complaints include chest pain, fever, cough or dyspnoea, but clinical presentation can be non-specific and variable, which makes early diagnosis challenging.

The classic presentation is that of a relatively young patient presenting with fever, chest pain and symptoms of an acute respiratory illness. However, elderly patients or patients with multiple comorbidities can also present insidiously or with non-specific symptoms such as malaise and loss of appetite.

Risk Factors

Risk factors associated with pleural infections include immunosuppression, diabetes, male gender, poor oral hygiene, gastro-oesophageal reflux disease and alcohol excess. However, there is currently no validated risk prediction tool to identify patients who are at high risk of developing infection in the pleural space.

Most pleural infections are community-acquired, accounting for 86% of all pleural infections in a local study.

In community-acquired pleural infections, gram positive aerobic bacteria predominate. Streptococcus anginosus is the most common causative organism by far, accounting for almost half of all culture-identified organisms, followed by methicillin-susceptible Staphylococcus aureus.

Nevertheless, gram-negative bacteria particularly Klebsiella pneumoniae, can cause community acquired pleural infections. Polymicrobial infections (including anaerobic bacteria) are also common, necessitating empiric broad spectrum antimicrobial cover.

MANAGEMENT IN PRIMARY CARE

The priority for clinicians in both the primary care and hospital setting is to have a high index of suspicion for pleural infections.

Clinical suspicion based on history and clinical examination should prompt further evaluation with chest X-ray imaging, which is a useful ‘screening’ and diagnostic tool in this respect. Clinicians will also have to evaluate the important distinction between the so-called ‘simple’ parapneumonic effusion and pleural infection. While the former usually resolves with antibiotic therapy targeted at the underlying pneumonia, pleural infections often require prompt pleural drainage and extended antibiotic therapy.

Once a diagnosis of pleural infection is suspected, evaluation at a hospital setting is recommended to facilitate further clinical and radiological assessment (ultrasonography and/or computed tomography scans), and consideration for chest drain insertion and other treatment modalities.

Treatment of pleural infection requires a multidisciplinary approach, where administration of intrapleural fibrinolytics and enzymatic therapy (e.g. alteplase/DNase) or video-assisted thoracoscopic surgery (breakdown of septations and decortication) may be employed.

CONCLUSION

Pleural infection remains a formidable medical challenge. The increasing incidence and intricate clinical presentation make diagnosis complex. Increased awareness in both the primary care setting and the hospital ‘front door’ is key to early recognition and treatment.

Successful treatment involves prompt antibiotic therapy, pleural drainage, and where appropriate, timely intrapleural therapy or surgery to minimise the significant morbidity and mortality associated with this condition.

REFERENCES

1. Roberts ME, Rahman NM, Maskell NA, et al. British Thoracic Society Guideline for pleural disease. Thorax 2023;0:1-34.
2. Chalmers JD, Singanayagam A, Murray MP, Scally C, Fawzi A, Hill AT. Risk factors for complicated parapneumonic effusion and empyema on presentation to hospitalwith community-acquired pneumonia. Thorax. 2009;64(7):592–7
3. Brims F, Popowicz N, Rosenstengel A, Hart J, Yogendran A, Read CA, et al. Bacteriology and clinical outcomes of patients with culture‐positive pleural infection inWestern Australia: A 6‐year analysis. Respirology. 2019;24(2):171–8
4. Goh KJ, Chew WM, Ong JCL, et al. A retrospective cohort study evaluating the safety and efficacy of sequential versus concurrent intrapleural instillation of tissueplasminogen activator and DNase for pleural infection. Pulm Med 2023;6340851.
5. Yong GKW, Wong JJJ, Zhang X, et al. Intrapleural fibrinolytic therapy for pleural infections: outcomes from a cohort study. Ann Acad Med Singap 2024;53:724-33.

Dr Goh Junyang Ken obtained his medical degree from Duke-NUS Medical School in 2012. He obtained specialist accreditation in Respiratory Medicine and Intensive Care Medicine in 2018 and 2019 respectively and is currently a Consultant with the Department of Respiratory and Critical Care Medicine at Singapore General Hospital. Dr Goh completed an Advanced Pleural Fellowship at the Oxford Pleural Unit (Oxford University Hospitals Trust) under Professor Najib Rahman in 2023, and currently leads the Pleural Service at the Singapore General Hospital.

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