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Infectious Disease and Microbiology – Pleural Effusion and Fever
Basics and Definitions
A pleural effusion is the accumulation of fluid in the pleural space due to increased production or decreased absorption. Light’s criteria distinguish transudates from exudates with high sensitivity and specificity. An exudative effusion meets at least one of the following: pleural fluid protein/serum protein >0.5, pleural fluid LDH/serum LDH >0.6, or pleural fluid LDH greater than two-thirds the upper limit of normal serum LDH. Parapneumonic effusions occur secondary to bacterial pneumonia and are classified as uncomplicated (free-flowing, sterile, resolve with antibiotics), complicated (low pH, low glucose, loculated), or empyema (gross pus in the pleural space). Empyema may be simple (single locule) or complex (multiloculated), most commonly caused by Streptococcus pneumoniae.
Clinical Approach
Symptoms depend on etiology and include dyspnea, pleuritic chest pain, fever, weight loss, edema, and hemoptysis. Evaluation requires careful history, physical examination, and diagnostic thoracentesis. Initial pleural fluid analysis includes protein, LDH, glucose, amylase, cytology, and cell count. In febrile patients or when fluid is turbid or malodorous, Gram stain, aerobic and anaerobic cultures are essential, with consideration of pH, acid-fast bacilli smear and culture, and fungal studies. Pleural biopsy and bronchoscopy are indicated when tuberculosis or malignancy is suspected. Thoracoscopy or open pleural biopsy is reserved for unresolved diagnostic cases.
Epidemiology
Pleural effusions account for approximately 1.5 million cases annually in the United States. Tuberculosis is the leading cause of exudative effusions worldwide but is less common in the US. In intensive care units, about 10% of pleural effusions are parapneumonic.
Etiology
Transudative effusions result from systemic factors and are rarely associated with fever; causes include heart failure, nephrotic syndrome, cirrhosis, constrictive pericarditis, pulmonary embolism, and myxedema. Exudative effusions arise from local pleural disease and commonly present with fever; causes include infections (bacterial, mycobacterial, fungal, viral, parasitic), malignancy, pulmonary embolism, and connective tissue diseases. Other causes include pancreatitis, esophageal rupture, chylothorax, hemothorax, drug reactions, asbestos-related disease, post-cardiac injury syndromes, radiation, sarcoidosis, uremia, and yellow nail syndrome. In patients with AIDS, noninfectious causes predominate, though bacterial pneumonia, Pneumocystis jirovecii, tuberculosis, and disseminated fungal infections remain important. Tuberculous pleurisy is typically an exudate with low pH, normal-to-low glucose, and lymphocytic predominance. Vertebral osteomyelitis, hantavirus pulmonary syndrome, parasitic infections, and Chagas disease should also be considered in appropriate settings.
Diagnosis
Acute febrile illness with chest pain and leukocytosis suggests aerobic bacterial pneumonia with parapneumonic effusion. Subacute presentations with weight loss and aspiration risk suggest anaerobic infection. Tuberculous pleuritis presents with fever, dyspnea, pleuritic pain, and weight loss, though pleural pain may be absent.
Diagnostic Tests and Interpretation
Neutrophil-predominant effusions suggest parapneumonic effusion, pulmonary embolism, or pancreatitis, while lymphocyte predominance favors tuberculosis, malignancy, or rheumatologic disease. Eosinophilic effusions occur in hemothorax, parasitic disease, asbestos exposure, pulmonary embolism, and Churg–Strauss syndrome. Low pleural glucose (<60 mg />L) and low pH (<7.3) indicate complicated infection, malignancy, or rheumatoid pleuritis. acid-fast stains and cultures have low sensitivity in tuberculous pleurisy; pleural biopsy significantly improves diagnostic yield. ada levels>70 U/L and elevated interferon-γ support tuberculosis, with reduced utility in low-prevalence regions. Elevated pleural amylase suggests pancreatic disease, lung adenocarcinoma, or esophageal rupture. Imaging includes chest radiography, ultrasound for septations, CT for parenchymal disease or embolism, and PET scanning for suspected malignancy.
Management
Uncomplicated parapneumonic effusions require antibiotics alone. Complicated effusions require tube thoracostomy, often with intrapleural fibrinolytics. Persistent loculated effusions or empyema require thoracoscopy or decortication. Simple empyema is managed with large-bore chest tubes; complex empyema often necessitates surgical intervention.
Follow-Up and Prognosis
Persistently unexplained effusions require reevaluation for tuberculosis and pulmonary embolism. Untreated tuberculous pleurisy frequently progresses to active tuberculosis within several years, mandating full antituberculous therapy. Tuberculous empyema may lead to severe pleural fibrosis and restrictive lung disease.
Basics and Definitions
A pleural effusion is the accumulation of fluid in the pleural space due to increased production or decreased absorption. Light’s criteria distinguish transudates from exudates with high sensitivity and specificity. An exudative effusion meets at least one of the following: pleural fluid protein/serum protein >0.5, pleural fluid LDH/serum LDH >0.6, or pleural fluid LDH greater than two-thirds the upper limit of normal serum LDH. Parapneumonic effusions occur secondary to bacterial pneumonia and are classified as uncomplicated (free-flowing, sterile, resolve with antibiotics), complicated (low pH, low glucose, loculated), or empyema (gross pus in the pleural space). Empyema may be simple (single locule) or complex (multiloculated), most commonly caused by Streptococcus pneumoniae.
Clinical Approach
Symptoms depend on etiology and include dyspnea, pleuritic chest pain, fever, weight loss, edema, and hemoptysis. Evaluation requires careful history, physical examination, and diagnostic thoracentesis. Initial pleural fluid analysis includes protein, LDH, glucose, amylase, cytology, and cell count. In febrile patients or when fluid is turbid or malodorous, Gram stain, aerobic and anaerobic cultures are essential, with consideration of pH, acid-fast bacilli smear and culture, and fungal studies. Pleural biopsy and bronchoscopy are indicated when tuberculosis or malignancy is suspected. Thoracoscopy or open pleural biopsy is reserved for unresolved diagnostic cases.
Epidemiology
Pleural effusions account for approximately 1.5 million cases annually in the United States. Tuberculosis is the leading cause of exudative effusions worldwide but is less common in the US. In intensive care units, about 10% of pleural effusions are parapneumonic.
Etiology
Transudative effusions result from systemic factors and are rarely associated with fever; causes include heart failure, nephrotic syndrome, cirrhosis, constrictive pericarditis, pulmonary embolism, and myxedema. Exudative effusions arise from local pleural disease and commonly present with fever; causes include infections (bacterial, mycobacterial, fungal, viral, parasitic), malignancy, pulmonary embolism, and connective tissue diseases. Other causes include pancreatitis, esophageal rupture, chylothorax, hemothorax, drug reactions, asbestos-related disease, post-cardiac injury syndromes, radiation, sarcoidosis, uremia, and yellow nail syndrome. In patients with AIDS, noninfectious causes predominate, though bacterial pneumonia, Pneumocystis jirovecii, tuberculosis, and disseminated fungal infections remain important. Tuberculous pleurisy is typically an exudate with low pH, normal-to-low glucose, and lymphocytic predominance. Vertebral osteomyelitis, hantavirus pulmonary syndrome, parasitic infections, and Chagas disease should also be considered in appropriate settings.
Diagnosis
Acute febrile illness with chest pain and leukocytosis suggests aerobic bacterial pneumonia with parapneumonic effusion. Subacute presentations with weight loss and aspiration risk suggest anaerobic infection. Tuberculous pleuritis presents with fever, dyspnea, pleuritic pain, and weight loss, though pleural pain may be absent.
Diagnostic Tests and Interpretation
Neutrophil-predominant effusions suggest parapneumonic effusion, pulmonary embolism, or pancreatitis, while lymphocyte predominance favors tuberculosis, malignancy, or rheumatologic disease. Eosinophilic effusions occur in hemothorax, parasitic disease, asbestos exposure, pulmonary embolism, and Churg–Strauss syndrome. Low pleural glucose (<60 mg />L) and low pH (<7.3) indicate complicated infection, malignancy, or rheumatoid pleuritis. acid-fast stains and cultures have low sensitivity in tuberculous pleurisy; pleural biopsy significantly improves diagnostic yield. ada levels>70 U/L and elevated interferon-γ support tuberculosis, with reduced utility in low-prevalence regions. Elevated pleural amylase suggests pancreatic disease, lung adenocarcinoma, or esophageal rupture. Imaging includes chest radiography, ultrasound for septations, CT for parenchymal disease or embolism, and PET scanning for suspected malignancy.
Management
Uncomplicated parapneumonic effusions require antibiotics alone. Complicated effusions require tube thoracostomy, often with intrapleural fibrinolytics. Persistent loculated effusions or empyema require thoracoscopy or decortication. Simple empyema is managed with large-bore chest tubes; complex empyema often necessitates surgical intervention.
Follow-Up and Prognosis
Persistently unexplained effusions require reevaluation for tuberculosis and pulmonary embolism. Untreated tuberculous pleurisy frequently progresses to active tuberculosis within several years, mandating full antituberculous therapy. Tuberculous empyema may lead to severe pleural fibrosis and restrictive lung disease.
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