A 13-year-old boy with asthma, gastroesophageal reflux (GERD), multiple food allergies, and history of 2 uncomplicated right middle lobe pneumonias within the last year presented to the emergency room with persistent cough and fever (max 102˚F) for 10 days, despite macrolide antibiotic treatment. A chest radiograph was performed in the emergency, followed by an esophagram/upper GI and CT examinations after admission (Fig 1).
Cavitary mass with internal air-fluid level
Although uncommon, complications from pneumonia in children do occur, and recent literature has suggested that they are increasing in prevalence.1 Complications of pneumonia include parapneumonic effusions, empyemas, lung abscesses, necrotizing pneumonia (multiple small abscesses), and empyema neccessitatis. These complications can lead to extended hospital admission and increased morbidity.1 Children usually recover completely without significant sequelae, unlike adults who often have underlying lung disease or co-morbidities.2 Although surgical intervention is often required to treat adults with these same complications due to high associated mortality (20%), children often need only conservative medical management.2,3
Ultrasound is invaluable for evaluation of the pediatric chest, as it involves no ionizing radiation, can be performed bedside, and allows excellent evaluation of simple or complex parapneumonic effusions and abscesses. Ultrasound should be used as first-line confirmation of a pleural effusion, as well as to guide treatment and need for percutaneous drainage, as it can readily distinguish between fluid, consolidations, and loculations.2 Ultrasound detects thin septae, fibrin strands, internal debris, and loculations in complex effusions, which are usually not evident by CT. CT should be reserved for complicated cases with worsening respiratory function or immunocompromised patients.2
For parapneumonic effusions and abscesses which are expanding or compromising respiratory function, percutaneous drainage should be considered. Ultrasound guidance is preferred, as it allows for realtime localization of collections or abscesses. Direct visualization under ultrasound is advantageous for catheter insertion and manipulation through septae or thick loculations that can interfere with drainage. In children, CT should not be used routinely; CT-guided drainage should be avoided, when possible, due to the potential risks of ionizing radiation in the pediatric population.2 Adjunctive tissue plasminogen activator (tPA) can be administered via a percutaneous catheter to promote drainage of an abscess by lysing fibrin strands.4 At our institution, we routinely use tPA for drainage of loculated effusions and empyemas with good results, although use of tPA is controversial in the literature. One major complication of percutaneous drainage is the formation of a bronchopleural fistula; however, these may also occur directly from the complicated pneumonia alone. Tissue plasminogen activator is contraindicated if a bronchopleural fistula is present. Other major complications of percutaneous drainage include pneumothorax and hemorrhage.
Pulmonary abscesses can be classified as primary or secondary. Primary pulmonary abscesses in a child are usually a complication of pneumonia or aspiration.5 Secondary pulmonary abscesses can be caused by underlying lung disease or pulmonary abnormality, either congenital or acquired. Secondary abscesses can also be seen in patients at risk of aspiration, such as those with neurodevelopmental abnormalities (seizures, muscular dystrophy) or esophageal abnormalities (achalasia, tracheoesophageal fistula, strictures).6 Underlying pulmonary disorders, such as cystic fibrosis or congenital lung malformation, are also implicated as causes of recurrent pneumonia and pulmonary abscesses.6
Radiographs often show a large cavitary mass with thick walls; air-fluid levels may be seen. CT may not be necessary on a routine basis, as radiographs may be sufficient for the diagnosis. Contrast-enhanced CT may be useful for delineation and extent of disease but should only be performed for worsening respiratory symptoms. On CT, pulmonary abscesses are usually round with thick walls and irregular luminal surfaces. Vessels and bronchi terminate abruptly at the abscess edge, and the walls of the abscess form acute angles with the chest wall.7 On ultrasound, abscesses are seen as a thick-walled collections containing echogenic pus and debris. Internal septations and bright echogenic foci with dirty shadowing from intraluminal air may be seen.
Lung abscesses in children often resolve with medical treatment alone. Usually, at least a 3-week course of intravenous antibiotics is needed with coverage for anaerobic organisms, which are most commonly implicated in pulmonary abscesses.8,9 However, in some cases, the patient may require intervention with ultrasound-guided percutaneous drainage. Abscess drainage is indicated if the patient has persistent fever, sepsis, or worsening respiratory symptoms which are not responding to medical treatment alone.2 Other indications include an enlarging abscess collection or imminent rupture into a bronchus. Percutaneous ultrasound-guided drainage of a recalcitrant pulmonary abscess is safe and effective, avoids surgery, and helps to shorten the clinical course of the illness.5
Empyemas form as a complication of pneumonia and are characterized as complex collections of pus within the pleural space. Inflammation of the pleura leads to increased vascular permeability and fibrin production, resulting in pleural adhesions which can form a thick rind.3 Blockage of lymphatic drainage leads to increasing fluid accumulation, further compressing and compromising the adjacent lung parenchyma.3 Empyema formation evolves in 3 stages: 1) an exudative phase with inflammation and simple effusion of low cellular count; 2) a fibrinopurulent phase in which fibrin covers the pleura and forms thin septae and loculations; and 3) an organizing phase with formation of a thick fibrous capsule which prevents lung re-expansion.3
On radiographs, empyemas appear as loculated effusions with convex borders or consolidated lung. On CT, empyemas are often lentiform in shape, compress vessels and bronchi, and form obtuse margins with the chest wall.7 Uniform thickening of the visceral and parietal pleura form the “split pleural” sign previously described in the literature.7 Pleural enhancement is usually present and greatest along the visceral pleural. Ultrasound is important, as it can distinguish fluid which is not readily defined on chest radiographs. Ultrasound of an empyema defines pleural thickening, loculations (which may have a honeycombed appearance), fibrous strands, and septae in the pleural space.
Most empyemas can be treated conservatively with antibiotics and chest tube drainage.2 At our institution, adjunctive tPA is used when draining empyemas. Video-assisted thoracoscopic surgery is reserved for severe cases which do not respond to conservative management. Within the current literature, there is still no clear consensus on surgical treatment in children.1-3
Necrotizing pneumonia or cavitary necrosis is a severe complication of pneumonia with destruction of the lung parenchyma and gangrenous necrotizing changes; there may be formation of multiple small abscesses. Necrosis develops as a result of ischemia caused by inflammation with occlusion of capillary vessels.6 Although the illness is severe, children usually recover fully without the need for surgical intervention or severe sequelae, contrary to what is typically seen in adults.6
On chest radiographs, necrotizing pneumonia appears as a large consolidation which may or may not contain small lucencies or cavities. CT is more sensitive than radiographs for evaluation of cavitation.6 Unlike pulmonary abscesses, necrotizing pneumonia on CT demonstrates loss of the normal lung architecture, decreased parenchymal enhancement, and absence of a thick wall. On ultrasound, consolidated lung will have multiple small cystic and hypoechoic areas with decreased or only mild peripheral color flow.
Pulmonary abscess secondary to occult aspiration from underlying esophageal achalasia.
In summary, children with recurrent pneumonia should receive follow-up imaging to document resolution of the infectious process and exclude an underlying pathologic process or mass. In our patient, the underlying cause of recurrent pneumonia — and ultimately abscess formation — was occult aspiration due to primary achalasia. Although our patient had been treated clinically in the past for gastroesophageal reflux, an upper GI was not preformed until an observant radiologist recommended the study for a dilated esophagus noted on chest radiographs.
Pulmonary abscesses in children are commonly related to pneumonia or aspiration. Children usually have an excellent prognosis with conservative medical management and no significant long-term sequelae. Percutaneous ultrasound-guided drainage should be considered if clinical symptoms do not improve, the abscess enlarges, or there is impending rupture into a bronchus. First-line ultrasound should be considered to distinguish between complex and simple parapneumonic pleural effusions, as it is effective in delineating loculations and septations.
Crum RP, Restrepo R, Altman N. Cavitary Lung Mass in a Febrile Child. J Am Osteopath Coll Radiol. 2014;3(2):21-24.