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

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.