Aspiration pneumonia in children: an iconographic essay*

In most cases of aspiration pneumonia in children, the disease is specific to this age group. Clinical and radiological correlation is essential for the diagnosis. The present pictorial essay is aimed at showing typical images of the most common etiologies.

supplemented by computed tomography and esophagealgastroduodenal seriography (EGDS) are almost always enough to make the diagnosis (13,18) .

DISCUSSION
The function of conducting food from the mouth to the stomach involves a joint action of the muscles innervated by the IX, X, XI and XII cranial pairs (12,19) . Due to immaturity, central nerve system injuries or drugs effects, this mechanism may be disturbed, and part of the food is diverted into the airways (Figures 1, 2 and 3). In such situations, radiological findings are similar to those observed in adult individuals (13) .

INTRODUCTION
Recently, the Brazilian radiological literature has been worried a lot about the relevance of imaging methods in the improvement of the diagnosis in pediatrics (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11) . Aspiration pneumonias result from passage of the oropharyngeal, esophageal or stomach contents into the lower respiratory tract (12) . The resulting compromise of the lungs depends on the nature and amount of aspirated material (12) . In the pediatric group, aspiration occurs most frequently because of deglutition abnormality, congenital malformations and gastroesophageal reflux. Lipoid pneumonia is more rarely observed and is always iatrogenic (13)(14)(15)(16)(17) . Chest radiography, sometimes

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Any stasis resulting from narrowing of the esophageal lumen may lead to aspiration (18)(19)(20) . Usually, this does not occur in cases of acquired achalasia and stenosis, because children frequently adapt themselves to such conditions. Esophageal atresia usually is detected and surgically corrected before causing significant aspiration (18,19) . Amongst those cases of compression by anomalous vessels, compression by double aortic arch is the one that most frequently causes symptoms (13,21) (Figure 4). The diagnosis of H-type tracheoesophageal fistula may be late, as contrast-enhanced images not always can easily demonstrate it (13,18) (Figure 5).     Figure 6. A twenty-month-old female child presenting with fever and cough. A: Anteroposterior chest radiography revealing the presence of bilateral, diffuse, ill defined, coalescent opacities in the middle lobe, conditioning the partial fading of the cardiac silhouette. B: Computed tomography, axial section identifying bilateral, predominantly central consolidations with air bronchograms. C: EGDS demonstrating reflux. As no clinical and radiological improvement was observed after antibiotic therapy, lung biopsy was indicated and showed foreign body granulomas and vegetal fibers presumably coming from gastroesophageal reflux. After appropriate treatment, clinical and radiological healing was observed.

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Respiratory manifestations stand out in the wide spectrum of gastroesophageal reflux disease (18)(19)(20)(21) . More than highlighting the presence of reflux -whose diagnosis is essentially clinical -, EGDS plays a relevant role in the demonstration of either normal or pathological anatomy (19)(20)(21) . In the absence of anatomical alterations, reflux is considered to be primary, resulting from generally transient immaturity of the distal esophageal high pressure zone (19,20) (Figure 6). Surgical intervention is indicated in cases of reflux secondary to partial or total obstruction -usually hypertrophic pyloric stenosis or malformations of the second portion of the duodenal arch ( Figure 7) (13,19,20) .
Lipoid pneumonia is not related to anatomical or functional anomalies (13,15) . Aspiration occurs because of the use of mineral oil in the treatment of intestinal constipation (Figure 8) or as an adjuvant in cases of intestinal subocclusion caused by Ascaris lumbricoides (4) . The oil inhibits the cough reflex and ciliary motion, and silently reaches the alveoli. Because of the difficulty in removing the oil from the lungs, such pneumonias present a slow evolution pattern (14,15) .

IMAGING FINDINGS
Aspiration pneumonias involve the alveoli (12,20,21) . The literature reports a most frequent involvement of the posterior segments of the upper lobes and the upper segments of the lower lobes (12,13,18) . This happens as aspiration occurs with the child in dorsal decubitus, like in most gastroesophageal reflux and vomiting episodes (12,13) . In other situations, such as tracheoesophageal fistula and lack of motor coordination, other pulmonary segments may be affected (19)(20)(21) (Figures 2  and 5). In most of cases, chest radiography and EGDS are sufficient to confirm the clinical suspicion; eventually, high resolution computed tomography is useful (13) . Aspiration may result in atelectasis or pneumonia, the latter with or without atelectatic component (13) . The absence of fever suggests pure atelectasis (22) (Figures 3 and 9).  After four-day anti-reflux treatment, the symptoms disappeared and chest radiography was normal. C: Normal anteroposterior chest radiography after treatment for gastroesophageal reflux disease.
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