An empyema can develop in multiple anatomical cavities: pleural cavity, thoracic cavity, uterus , appendix , meninges , gallbladder , brain and joints. However, the pleural variant of empyema is probably the most common form: for this reason, the focus in this article will be exclusively on pleural empyema .
Pleural empyema – otherwise known as pyothorax – outlines a collection of pus in the pleural cavity, the space between the lung and the inner surface of the chest wall.
The empyema can be limited to a specific portion of the pleural cavity or involve the entire cavity.
The pathogenesis of pleural empyema can be related to multiple causal elements:
- sub-phrenic/pulmonary abscesses
- infections ( bacterial , parasitic and nocosomal) from lung laceration, propagation of pathogens via the lymphatic /blood/trans-diaphragmatic route
- surgical interventions
- esophageal perforation
- superinfection of a hemothorax (presence of blood in the pleural fluid ) which was initially sterile
Pleural empyema is often described as a complication of Streptococcus pneumoniae infections ( pneumonia ): in similar circumstances, the pleural affection takes on the more precise connotation of meta-pneumonic empyema . Lung abscess is also among the most frequent etiopathological elements involved in empyema.
Only in rare cases, empyema can be a consequence of thoracentesis , a diagnostic practice aimed at collecting a sample of pleural fluid using a needle inserted directly into the pleural cavity.
The pathogens most involved in the manifestation of empyema are Staphylococcus aureus , streptococci, gram negative bacteria ( Klebsiella pneumoniae , Escherichia coli , Proteus , Salmonella , Acinetobacter baumannii ), anaerobes (Bacteroides) and parasites (Paragonimus).
The symptoms, as well as their intensity, depend on the severity of the empyema. Generally speaking, hospitalized empyema patients complain of asthenia , chills , weight loss , dyspnea , chest pain , fever , general malaise and cough. Chest pain is exacerbated by deep breathing and coughing .
In the vast majority of diagnosed empyemas, a constant trend of the disease was observed, distinguishable in three phases:
- Exudative phase of empyema (acute empyema). This phase lasts approximately two weeks and is characterized by exudative inflammation with poor fibrin synthesis . The pleural fluid is not very dense and has few cells. Only an immediate and specific antibiotic therapeutic intervention carried out in this phase can ensure complete restoration to integrum .
- Fibrino- purulent phase of empyema (frank empyema): after the first 14 days from the onset of empyema, the second phase begins, in which an enormous quantity of polymorphonuclear granulocytes , bacteria and necrotic material is produced , associated with a conspicuous fibrin deposition. The co-presence of these substances favors the chronicity of the empyema. This phase begins during the third week from the onset of the condition, and ends after 14 days.
- Organization phase (chronic empyema): it constitutes the last stage, in which the visceral pleura is fixed with the parietal pleura, to the point of forming a sort of resistant rind or armor that encloses the lung, limiting its mechanics.
Due to an inflammatory and fibrous reaction, the pleura that delimits the empyema thickens excessively and becomes inelastic: in doing so, the lung is denied the possibility of re-expanding.
To minimize the risk of complications, antibiotic therapy should begin from the very first symptoms, therefore during the exudative phase of the empyema. A delay in treatment can favor the onset of complications:
- spread of the infection
- bronchopleural fistulas: the purulent material that is not evacuated through surgery can drain spontaneously into the bronchial side , resulting in the appearance of foul-smelling purulent sputum
- fibrothorax: clinical condition characterized by the reduction of width, expandability and parietal elasticity of the hemithorax. The result is functional damage with severe restrictive ventilatory deficit.
- sepsis: alarming and exaggerated Systemic Inflammatory Response (SIRS), sustained by the body following a bacterial insult
- empyema necessitatis: clinical condition in which pus collects in the subcutaneous tissue and fistulizes outside the chest. This form of empyema is a typical complication of Mycobacterium tuberculosis infections .
The diagnosis of pleural empyema is established when the quantity of leukocytes in the pleural fluid is greater than at least 15,000 units per mm3 and the presence of microorganisms in situ is detected.
Routine diagnostic techniques include:
- chest x-ray
- Chest CT
- Culture examination after thoracentesis
From the diagnostic results, the purulent pleural fluid presents peculiar biochemical characteristics, reported in the table.
|Pleural LDH||> 200 U/dl|
|Pleural LDH/serum LDH||> 0.6|
|Glucose||< 40-60 mg/dl|
|Leukocytosis||15,000-30,000 polymorphonuclear leukocytes (PMN)/mm 3|
|Pleural fluid proteins||> 3g/dl|
The main goal of treatment for empyema is twofold. On the one hand it is necessary to remove the bacterium or in any case the pathogen with an appropriate pharmacological (antibiotic) treatment, on the other it is essential to constantly evacuate the purulent material that accumulates in the pleural cavity.
While waiting for the results of the antibiogram , it is recommended to start the treatment by administering aminoglycoside antibiotics such as gentamicin and tobramycin, associated with a broad-spectrum penicillin .
The treatment of empyema depends on the developmental stage in which the disease is diagnosed.
If in the initial stage thoracentesis and antibiotic therapy are sufficient for the patient’s complete recovery, in the subsequent stages of empyema the therapy is more complex. As early as the third week from the onset of symptoms (phase II), the doctor must subject the patient to closed drainage, clearly always associating antibiotic treatment . Stage III, the most dangerous, requires pleural decortication, which consists in the removal of the visceral pleura.
The prognosis depends on when antibiotic treatment is started and the purulent fluid is removed. Before the introduction of antibiotics into therapy, empyema-related mortality was significantly higher.