Review and study of cases of infectious pleural effusion

Introduction:

Up to 40% of patients with acute bacterial pneumonia are associated with pleural effusion (PE) and 5 – 10% of these develop an empyema. The pleural liquid microbiological study is often unsuccessful for various reasons: truly sterile pleural liquid, antibiotic treatment prior to inadequate technique to detect certain germs (Legionella, anaerobic germs...), the low number of germs and low sensitivity of the techniques used. As such, many infectious pleural effusions fail to receive a true etiological diagnosis.

Material and methods:

Retrospective study of the clinical histories of 28 patients with infectious PE admitted to our hospital's Respiratory Department between May 2016/January 2017. Patients with parapneumonic and tuberculous PE and empyema were included. Anamnesis, physical examination and radiological imaging were evaluated. The results of diagnostic thoracentesis and pleural biopsy performed were collected. Thoracic ultrasound was used to locate small effusions, find the puncture point and characterise the effusions. Cases that presented pleural liquid that was purulent in appearance and those in which the micro-organism responsible was isolated were considered empyemas. Etiology of the effusion: 57% parapneumonic; 36% empyema; 7% tuberculous. The pathogen was isolated in 8 patients (80%) of those with empyemas, with the most frequent micro-organism being Streptococcus intermedius (4 cases), followed by Streptococcus anginosus (3 cases) and H. influenzae (1 case).

Results:

The histological confirmation of granulomas via pleural biopsy or Ziehl stain/mycobacterial culture was necessary for the diagnosis of tuberculous PE. The sample presented an average age of 56.3 and 18 patients were active smokers or former smokers with an index of cumulative exposure of 35 packs/year. They remained hospitalised for an average of 18 days.

Conclusions:

• The diagnostic yield of the bacteriology was very high for the group of empyemas.

• As in other series, it was not possible to determine the microbiological etiology of (parapneumonic) infectious pleural effusion by means of a clinical radiological diagnosis.

• The use of thoracic ultrasound has been standardised in the management of this pathology and is used in a high percentage of suspected cases of infectious pleural effusion.