Empyema differential diagnosis

Empyema Microchapters
Patient Information
Overview
Classification Subdural empyema Pleural empyema
Differential Diagnosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Differential diagnosis

Empyema must be diffrentiated from pneumonia, lung abscess, lung cancer and parapneumonic effusions as shown below:

Variable	Empyema Thoracis	Lung abscess	Pleural effusion	Pneumonia	Lung cancer
Presentation	Variable presentation but may follow long standing pneumonia	Usually has history of aspiration pneumonia, alcoholics, drug abusers, seizure disorder, have undergone recent general anesthesia, or have a nasogastric or endotracheal tube.	Usually follows pneumonia as a complication	presents with fever, pleuritc chest pain, cough	mostly asymptomatic but may have cough productive with hemoptysis and chronic history of smoking
Causes	In general any bacteria can cause an empyema, however different bacteria are associated with different rates of empyema formation.[1]  Common causes include bacteroides, fusobacterium, haemophilus influenzae, pneumococcal infections, staphylococcus aureus, streptococcus, TB	Lung abscess is commonly caused by bacterial infections and these include bacteroides, peptostreptococcus and prevotella mostly after aspiration	Common causes of transudative pleural effusion include;[1][2][3][4][5] left ventricular failure, Nephrotic syndrome, and cirrhosis, while common causes of exudative pleural effusions[6] are bacterial pneumonia and malignancy	Pneumonia can result from a variety of causes, including infection with bacteria, viruses, fungi, parasites, and chemical injury to the lungs	Direct cause of lung cancers is DNA mutations that often result in either activation of proto-oncogenes (e.g. K-RAS) or the inactivation of tumors suppressor genes (e.g. TP53) or both. The risk of these genetic mutations may be increased following exposure to environmental components example smoking
Laboratory findings				Laboratory findings are non specific example leukocytosis, sputum samples for gram staining and culture. Other tests include urine antigen test, PCR, C-reactive protein and procalcitonin	The laboratory findings are non specific including: neutropenia, hyponatremia, hypokalemia, hypercalcemia, respiratory acidosis, hypercarbia, hypoxia, and tumor cells in sputum and pleural effusion cytology.
Physical examination				Physical examination increased respiratory rate, low oxygen saturation, difficulty breathing, bronchial breathe sounds, crackling sounds, or increased whispered pectoriloquy.
CXR			A homogenous opacification is noted at the affected side. The costophrenic angle is obliterated with a meniscus.	CXR shows areas of diffused opacities.
Chest ultrasound	Ultrasound in empyema is positive for suspended microbubble sign, air fluid level, curtains sign and loss of gliding sign.	Ultrasound in lung abscess is negative for suspended microbubble sign, curtains sign and loss of gliding sign but air fluid level may be seen,.	Ultrasonography is not needed in making diagnosis of pleural effusion however, chest or upper abdominal ultrasound may show subpulmonic effusion.	Not reqiured unless complicated with empyema
CT scan	Seen as a lung mass whose cavity is regular with smooth and regular lumen, well-defined defined boundary and shape changes with change in patient's position. Mass may resolve on antibiotics The split pleura sign is present (most reliable sign to differentiate empyema from lung abscess)	Lung mass whose cavity is rregular with undulated lumen, irregular-poorly defined boundary and shape does not change with change in patient's position. Mass may resolve on antibiotics		CT findings in pneumonia include:[1] Airspace consolidation Ground-glass oppacities Pleural effusion Hiliar and/or mediastinal lymphadenopathy Bronchiectasis Tree-in-bud appereance	Seen as a lung spiculated irregular solid mass that does not resolve on antibiotics