Pulmonary pneumatocele: its significance, aetiology, imaging features and follow-up

Clinical History

A four-month-old female child presented with the chief complaints of breathlessness for three weeks associated with dry cough, chest retraction, different tone of cry and fever since one day. She was tachycardic and tachypnoeic. On auscultation, bilateral ronchi with crepitations were heard. Blood culture revealed Staphylococcus aureus.

Imaging Findings

Chest radiograph showed a right upper zone consolidation along with a thin-walled, rounded radiolucent lesion in the left lower zone with no air-fluid levels, or calcifications within (Fig. 1). Chest CT revealed a thin-walled air-filled cavity measuring 3.3x3x3.2 cm in the basal segment of the left lower lobe, showing neither air-fluid level nor calcification (Fig. 2a & 3). In addition to this, atelectasis involving posterior segment of right upper lobe was also noted (Fig. 2b). Follow-up chest radiograph taken after 1 month showed resolution of the previously detected findings on imaging (Fig. 4).

Discussion

Pneumatoceles are cystic air-filled spaces within the lung parenchyma that result from an underlying inflammation or bronchial injury. [1] The mechanism behind the formation of a pneumatocele is believed to be necrosis of the lung parenchyma which allows one-way passage of air into the interstitial space. Causes include pneumonia, blunt chest trauma, hydrocarbon ingestion with aspiration, and chronic obstructive pulmonary disease. In children, pneumatoceles commonly occur as a complication to severe pneumonia. [2] Among the several pneumonia-causing organisms, bacterial pathogens, Streptococcus pneumonia and Staphylococcus aureus are the commonest pathogens causing pneumatoceles in children. Other organisms include Pseudomonas aeruginosa, Klebsiella, E.coli, Mycobacteria, Proteus mirabilis, Mycoplasma and Aspergillus fumigatus. Children with Hyperimmunoglobulin E syndrome (HIE) or Job’s syndrome are also prone to pulmonary pneumatoceles. [3-5] On radiographs and CT examinations, pneumatoceles appear as rounded thin-walled air-filled spaces in the lung parenchyma. [2] 85% of pneumatoceles are asymptomatic and resolve spontaneously or following treatment of the underlying primary infection without a clinical or imaging sequelae. [1, 3] Although CT for pneumatoceles with or without contrast is not routinely indicated, a contrast Chest CT was done for our patent as she had no previous antenatal scans available and also to rule out other possible differentials such as cystic adenomatoid malformation or bronchogenic cyst, each of which has a different treatment approach.
Another option would have been to "wait and watch", but as the clinical status of the patient was unstable, CT was chosen to narrow the differential diagnosis. Complications when present include rupture with resultant pneumothorax or bronchopleural fistula formation, rapid enlargement of the pneumatocele may cause cardio-pulmonary collapse, called tension pneumatocele, and secondary infection of a pneumatocele indicated by an air fluid level. First line management of a complicated pneumatocele is image-guided percutaneous, transcatheter aspiration and drainage. In conditions where this treatment strategy fails, the alternate lifesaving option is surgical procedures like lobectomy or pneumectomy.

Differential Diagnosis List

Final Diagnosis

Pulmonary pneumatocele complicating bacterial pneumonia

URL:	https://www.eurorad.org/case/13016
DOI:	10.1594/EURORAD/CASE.13016
ISSN:	1563-4086