Back to basics: lung volumes on pediatric chest X‐rays—pitfalls and diagnostic implications

Abstract Evaluating lung “volumes” when interpreting pediatric chest radiographs is useful for supporting the diagnosis of lung pathology in children. Lung volumes can be estimated using semi‐objective criteria such as anterior rib counting. Estimating lung volumes is one advantage plain radiographs have over other imaging modalities such as ultrasound or even cross‐sectional imaging (Computed Tomography and Magnetic Resonance Imaging, where volumes can be calculated, but remain difficult to quickly be appreciated subjectively or semi‐objectively in clinical practice). Lung hyperinflation is often a surrogate of air‐trapping and may be suggestive of diseases such as bronchiolitis. Identifying under‐inspired chest radiographs is also important to avoid misinterpreting findings related to low lung volumes as pathology, which is a significant diagnostic pitfall in children. This pictorial review will demonstrate the method for evaluating lung volumes, specifically for identifying lung hyperinflation as a surrogate of air‐trapping and under‐inspiration for avoiding false positive diagnoses.