Parapneumonic effusion
A parapneumonic effusion is a pleural effusion arising alongside bacterial pneumonia, ranging from a sterile uncomplicated collection to infected, loculated empyema. Diagnosis rests on thoracentesis with Light's criteria, pH, and glucose; complicated effusions and empyema require prompt chest tube drainage plus intravenous antibiotics, with intrapleural fibrinolytics or surgery for inadequate drainage.
- Topic reviewThe full article, organized the way the exam asks it.
- ABIM-format MCQsVignettes with an explanation for every wrong answer.
- Key factsThe numbers and thresholds worth memorizing, up front.
- AI tutorMedBrain answers the question you're stuck on.
What this article covers
- Overview
A parapneumonic effusion is a pleural effusion that develops on the same side as bacterial pneumonia, lung abscess, or bronchiectasis.
- Epidemiology
An estimated 20% to 40% of patients hospitalized with bacterial pneumonia develop a measurable parapneumonic effusion, and empyema complicates up to 10% of hospitalized community-acquired pneumonia (CAP).
- Risk factors
Delayed or mismatched antibiotic therapy: pneumonia treated late, or with an agent that misses the causative organism, allows bacterial invasion of the pleural space.
- Pathophysiology
Bacteria reach the pleural space by direct extension across an inflamed visceral pleura overlying a pneumonic focus, less often by hematogenous seeding or after chest trauma or surgery.
- Clinical features
Fever and pleuritic chest pain: sharp, inspiration-worsened pain over the affected hemithorax, often the symptom that flags a complicating effusion.
- Differential diagnosis
Tuberculous pleural effusion: also exudative, but classically lymphocyte predominant (more than 50%) with a nucleated cell count under 5,000/microliter and elevated adenosine deaminase, unlike the…
- Diagnosis
What establishes the diagnosis: confirmed by diagnostic thoracentesis in a patient with pneumonia and a new ipsilateral effusion; it is complicated when pH is below 7.2, glucose is below 60 mg/dL…
- Management
First-line, start empiric intravenous antibiotics covering Streptococcus pneumoniae, Streptococcus pyogenes, Staphylococcus aureus, and Streptococcus anginosus, with routine anaerobic coverage…
- Complications
Sepsis and bacteremia: untreated or inadequately drained pleural infection can seed the bloodstream, particularly with Staphylococcus aureus.
- Prognosis
Most uncomplicated parapneumonic effusions resolve fully with antibiotics and need no further intervention.
- Prevention
Prompt, pathogen-appropriate antibiotics for pneumonia: starting effective treatment early reduces the likelihood that a sterile effusion progresses to a complicated, infected collection.
Read the whole article
Subscribing to Internal Medicine opens every article, the full question bank and MedBrain, on the web, iPhone and Android.
Related articles
- Community-acquired pneumonia
Community-acquired pneumonia is a lower respiratory tract infection acquired outside the hospital that is diagnosed by a compatible clinical syndrome plus a new infiltrate on chest imaging, risk-stratified with CURB-65 or the Pneumonia Severity Index to guide site of care, and treated with empiric antibiotics chosen by site of care and comorbidity, escalating to cover MRSA or Pseudomonas aeruginosa when risk factors are present.
- Empyema
Empyema is frank pus or a culture/Gram-stain-positive bacterial infection of the pleural space, most often complicating pneumonia, that requires prompt drainage plus antibiotics rather than antibiotics alone.
- Pleural effusion
Pleural effusion is fluid accumulation in the pleural space from an imbalance of hydrostatic/oncotic pressure or increased capillary permeability; Light's criteria separate exudates from transudates, and management treats the underlying cause, with therapeutic thoracentesis, chest tube drainage, or pleurodesis for symptomatic or complicated effusions.
- Lung abscess
Lung abscess is a necrotic, pus-filled cavity in the lung parenchyma, most often from aspiration of oropharyngeal anaerobes in a patient with impaired airway protection, diagnosed by a cavity with an air-fluid level on imaging and treated with prolonged anaerobe-covering antibiotics plus postural drainage.
- Sepsis
Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection, identified by an acute rise in SOFA score of 2 points or more in a patient with known or suspected infection. Survival depends on recognizing the pattern early and completing the hour-1 bundle: lactate, blood cultures before antibiotics, broad-spectrum antibiotics such as cefepime 2 g IV every 8 hours, and 30 mL/kg crystalloid for hypotension or a lactate of 4 mmol/L or higher.
- Tuberculosis
Tuberculosis, caused by Mycobacterium tuberculosis, remains a leading global cause of infectious death and presents as latent infection, primary/secondary pulmonary disease, or extrapulmonary and disseminated (miliary) disease. Diagnosis rests on AFB smear, NAAT, and mycobacterial culture (the gold standard), and drug-susceptible active disease is treated with a four-drug regimen (isoniazid, rifampin, pyrazinamide, ethambutol) for 2 months followed by isoniazid plus rifampin for 4 to 7 months.