Pyopneumothorax is a potentially life-threatening condition marked by the presence of pus and air within the pleural cavity.
Pyopneumothorax could arise as a progression of either underlying hydropneumothorax or empyema. Therefore, etiological agents that cause these conditions could also play a role in the evolution of pyopneumothorax [1].
Symptoms of pyopneumothorax overlap with the symptoms seen in any severe lung infection and correlate with the degree of lung collapse on the ipsilateral side. Patients may present with pleuritic chest pain, severe cough and dyspnea, whilst also manifesting certain nonspecific symptoms such as fever, loss of appetite, loss of weight, and night sweats.
A recent history of pneumonia, pleural drainage, or penetrating injury may also be suggestive of the diagnosis [2] [3].
A variety of risk factors predisposing to pleural effusion or empyema that may progress to pyopneumothorax have been identified. Some of these predisposing factors are chronic lung disease, gastrointestinal reflux, and immunosuppression. Laboratory findings such as platelets >400 X 10*9, albumin < 30 g/L, sodium < 130 mmol/L and C-reactive protein >100 mg/L, and a history of either alcohol or drug abuse, suggests an increased risk of purulent pleural complications in patients admitted for community-acquired pneumonia [4].
Physical examination may reveal tachypnea, egophony, a dull note on percussion, decreased or absent breath sounds, rales, and rhonchi [5].
Laboratory and imaging techniques can be used to confirm the diagnosis. Leucocytosis is seen on a complete blood count, with the differential count suggestive of a left shift. Sputum should be collected in order to identify the etiological agent and to exclude tuberculosis. Antibiotic sensitivity testing should further be done on these samples. The presence of fever may mandate a blood culture.
Chest radiography is of prime importance for the differential diagnosis of pneumonia, pulmonary abscess, and empyema. An accurate diagnosis decides the course of future therapy, with pneumonia and lung abscess being treated with antibiotics, while empyema requires surgical evacuation of the pleural cavity [6] [7]. On a chest X-ray, lung abscess usually appears as a single round density with an air-fluid level. The empyema is characterized by the presence of an air-fluid level that extends to the chest wall. This is accompanied by the blunting of the costophrenic angle. Radiography in the lateral decubitus position may help determine whether the pleural collection is mobile or localized.
Chest CT should be performed when the clinical signs are characteristic for lung/pleural infection but the chest radiography is negative. Such a situation may be encountered in patients with immunosuppression. However, a CT-scan should be avoided in children due to the potential risks associated with excessive radiation exposure at a young age [8].
A Doppler ultrasonography may help distinguish a peripheral abscess from empyema by the presence of blood vessels in the tissue surrounding the abscess [9]. An ultrasonography control is needed during needle aspiration and drainage of the pleural cavity to avoid potential complications [10].
Pleural fluid obtained through diagnostic thoracentesis may reveal findings suggestive of an empyema. These pleural fluid characteristics include a purulent character of the fluid, elevated neutrophils, pleural fluid glucose levels < 60 mg/dl, lactate dehydrogenase >1000 IU/ml and the presence of microorganisms on pleural culture.