Case vignette
6yo M w/ asthma presents with 2wks of cough and 2d of F and SOB. No improvement with MDI. No trismus, drooling, or voice changes.
HR 137, BP 95/60, RR 22, SpO2 94%, T 38.3
Decreased breath sounds R lung base. No stridor or wheezing. Supple neck.
Your differential is highlighted by URI, pneumonia, asthma, pneumothorax, and atelectasis. A CXR is performed that appears unremarkable. You turn to US.
What do you see?
CP11 US1: normal lung fields anteriorly
CP11 US2: the visceral parietal pleural interface (VPPI) appears normal on the left but irregular, or "shredded," on the right (more inferiorly).
CP11 US3: hepatization (lung tissue looks like liver) with dynamic air bronchograms (pus/air moving in and out of view).
What do you do next?
Clinically, you suspect pneumonia. You recognize viral pneumonia is common in children, but the child is over 5yo and has subpleural consolidations >1cm. This is concerning for a bacterial etiology. Identifying hepatization and dynamic air bronchograms, you feel it is appropriate give antibiotics. You initiate a 7d course of high dose (90 mg/kg/d) TID amoxicillin. You give the child tylenol and ensure he tolerates PO. His vital signs improve and he looks sufficiently well to discharge with close follow up.
In 1-2d, he has substantial symptom improvement. He finishes his antibiotic course and does well.
Teaching points. Chest XR has notoriously high (and variable) false negative rates for diagnosing pneumonia, especially early in the disease process. (It can also lead to false positives, for example atelectasis can be mistaken for consolidation.) When your clinical suspicion for pneumonia is high, use ultrasound to augment your pre-test probability. This can be particularly helpful in pediatric populations to limit radiation and in critically ill patients who are difficult to perform 2 view CXRs on.
Multiple ultrasound findings can assist:
Early in pneumonia, B-lines and subpleural consolidations can be seen. Focal B-lines (not seen in this case) are the most sensitive but least specific sign. Next, the "shred sign" represents subpleural consolidations. It consists of an irregular, or shredded, visceral parietal pleural interface. This is also more sensitive but less specific for pneumonia. In pediatrics, >1cm of subpleural consolidation is suggestive of bacterial pneumonia.
Over time, purulent fluid in the alveoli can make the lung look like liver tissue ("hepatization"). In addition, you will often see "dynamic air bronchograms," which represent air movement in small bronchi. Hepatization and dynamic air bronchograms are less sensitive but the most specific for pneumonia. Note static air bronchograms are more suggestive of atelectasis.
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In regards to pediatric pneumonia, bacterial etiologies are uncommon in children <5yo. Atypical bacterial infections are especially unusual. Bacterial etiologies increase with age. Amoxicillin is an appropriate initial treatment for vaccinated children without penicillin allergy. If atypical pathogens are suspected, azithromycin is often given.
Note if this child had evidence of an asthma exacerbation (wheezing), concurrent treatment with bronchodilators and corticosteroids would be appropriate.
Sources:
- Biagi C, Pierantoni L, Baldazzi M et al. Lung ultrasound for the diagnosis of pneumonia in children with acute bronchiolitis. BMC Pulm Med. 2018;18:191. PMID 30526548 (https://pubmed.ncbi.nlm.nih.gov/30526548/)
- Lung Ultrasound: Pneumonia. James Rippey. Life in the Fast Lane. Nov 3, 2020. https://litfl.com/lung-ultrasound-pneumonia/. Accessed 4/12/21
-The Dynamic Air Bronchogram. Lichtenstein D, Meziere G, Seitz J. Chest. 2009; 135:1421-25. PMID 19225063 (https://pubmed.ncbi.nlm.nih.gov/19225063/)
Pediatric community acquired pneumonia