Empyema

What is empyema?

The term "empyema" identifies any generic accumulation of purulent liquid (rich in pus) inside a PRE-formed body cavity. The "empyema must therefore be distinguished from the" abscess, which consists in the "accumulation of purulent material inside" a NEO-formed cavity.

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 widespread form: for this reason, the attention in this article will be focused exclusively on pleural empyema.

Causes

Pleural empyema - otherwise known as pyothorax - delineates 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 confined to a specific portion of the pleural cavity or involve the entire cavity.
The pathogenesis of pleural empyema can be related to several causal elements:

• subphrenic / pulmonary abscesses
• infections (bacterial, parasitic and nocosomal) from lung laceration, propagation of pathogens by lymphatic / blood / trans-diaphragmatic route
• surgical interventions
• esophageal perforation
• sepsis
• superinfection of a hemothorax (presence of blood in the pleural fluid) initially sterile
• tuberculosis

Pleural empyema is often described as a complication of Streptococcus pneumoniae (pneumonia): in similar circumstances, pleural disease takes on the more precise connotation of meta-pneumonic empyema. Lung abscess is also one of the most frequent etiopathological elements involved in empyema.
Only in rare cases, empyema can be a consequence of thoracentesis, a diagnostic practice aimed at taking 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).

Symptoms

Symptoms, as well as their intensity, depend on the severity of the empyema. In general, patients admitted to empyema complain of asthenia, chills, weight loss, dyspnoea, chest pain, fever, general malaise and cough. Chest pain comes. exacerbated by deep breaths and coughing.
In the overwhelming majority of diagnosed empyema, a constant trend of the disease was observed, distinguishable in three phases:

1. Exudative phase of empyema (acute empyema). This phase lasts about two weeks and is characterized by an exudative inflammation with poor fibrin synthesis. The pleural fluid is not very dense and has few cells. Only an immediate antibiotic treatment. and specific, carried out at this stage, can ensure a complete returned ad integrum.
2. Fibrin-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 deposition of fibrin. The co-presence of these substances favors the chronicization of empyema. This phase begins during the third week from the onset of the disease, and ends after 14 days.
3. Phase of organization (chronic empyema): it constitutes the last stage, in which the visceral pleura is fixed with the parietal one, to form a sort of resistant shell or shell 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 so doing, the lung is denied the possibility of re-expanding.

Complications

To minimize the risk of complications, antibiotic therapy should start from the very first symptoms, therefore during the exudative phase of empyema. A delay in therapy can favor the onset of complications:

• spread of infection
• broncho-pleural fistulas: purulent material that is not evacuated by surgery can spontaneously drain into the bronchial side, resulting in the appearance of foul-smelling purulent sputum
• fibrothorax: clinical condition characterized by the reduction of the amplitude, expansibility and parietal elasticity of the hemithorax. This results in 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 subcutis and fistulises outside the chest. This form of empyema is a typical complication of Mycobacterium tuberculosis.

Diagnosis

The diagnosis of pleural empyema is ascertained when the amount 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 scan
• Culture examination after thoracentesis

From the diagnostic results, the pleural purulent fluid has peculiar biochemical characteristics, shown in the table.

Parameter

Indicative value

pH

< 7,20

Pleural LDH

> 200 U / dl

Pleural LDH / Serum LDH

> 0,6

Glucose

<40-60 mg / dl

Leukocytosis

15,000-30,000 polymorphonuclear leukocytes (PMN) / mm3

Pleural fluid protein

> 3g / dl

Treatment

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 treatment (antibiotic), on the other hand it is essential to constantly evacuate the purulent material that accumulates in the pleural cavity.
Pending the results of the antibiogram, it is recommended to start treatment by administering aminoglycoside antibiotics such as gentamicin and tobramycin, combined with a broad spectrum penicillin.
The therapy of empyema depends on the evolutionary stage in which the affection is diagnosed.
If in the initial stage thoracentesis and antibiotic therapy are sufficient for the complete recovery of the patient, in the subsequent stages of empyema the therapy is more complex. Already starting from the third week from the onset of symptoms (phase II) the doctor must undergo the patient to the closed drainage, clearly always associating antibiotic treatment. Stage III, the most dangerous, requires pleural decortication, which consists in the removal of the visceral pleura.
Prognosis depends on when antibiotic treatment is started and purulent fluid removed. Before the entry of antibiotics into therapy, mortality related to empyema was significantly higher.