Lung Ultrasound in Children: B-lines, Pleural Line, and Consolidation

The Role of Lung Ultrasound According to ESPR 2025

The European Society of Paediatric Radiology 2025 practical recommendations for imaging common pediatric lung diseases emphasize the role of ultrasound as an accessible method without ionizing radiation, useful for pleural pathology, peripheral inflammatory changes, and dynamic observation. The ESPR consensus text states that the choice of imaging method should depend on the clinical scenario, age, severity of the condition, and diagnostic question: ESPR, Imaging of common paediatric pulmonary diseases, 2025.

For the ultrasound diagnostician, the focus should not be on trying to 'see the entire lung' but on a standardized assessment of the accessible lung surface and pleura. Central lesions covered by aerated lung are not visualized by ultrasound, so a normal image does not exclude disease if clinical suspicion persists.

When Ultrasound is Particularly Informative

Ultrasound is most useful when the pathological process contacts the pleura or alters the pleural space. This is typical for parapneumonic effusion, empyema, peripheral pneumonic consolidation, atelectasis, pleural complications, and several emergency conditions. The method is also convenient for repeated studies as it allows for dynamic assessment without radiation exposure.

In pediatrics, the advantage is enhanced by the thin chest wall and frequent subpleural location of inflammatory changes. However, ultrasound does not replace clinical assessment and other imaging methods if central lung areas, the mediastinum, complications outside the ultrasound window, or an alternative diagnosis need evaluation.

Probe and Scanning Technique

The examination is performed with a probe that provides an optimal balance between pleural line resolution and depth of view. A linear probe is usually convenient for small children and pleural assessment; for larger children, deep effusion, or the need for a wider field, a convex or microconvex probe is used. Settings should allow visualization of the pleural line, ribs, air artifacts, and subpleural changes.

Scanning is conducted over the anterior, lateral, and posterior chest areas with comparison of symmetrical zones. The protocol should document the side, anatomical surface, pleural line characteristics, presence and distribution of B-lines, consolidation, bronchograms, and pleural fluid. In severe conditions, a focused bedside protocol is permissible, but the area of maximum tenderness, auscultatory changes, or radiological suspicion should be included.

Pleural Line: What to Describe

A normal pleural line appears as a thin hyperechoic line between the acoustic shadows of the ribs, moving synchronously with breathing. The report should describe not only the visualization but also its regularity, continuity, thickening, fragmentation, and reduction or absence of lung sliding.

An irregular, discontinuous pleural line combined with focal B-lines or subpleural hypoechoic areas supports an inflammatory or interstitial-alveolar pattern in the area. Isolated pleural line changes without clinical correlation require cautious interpretation: artifacts, incomplete probe contact, and respiratory movements can mimic pathology.

B-lines in Children

B-lines are vertical hyperechoic artifacts originating from the pleural line, extending deep into the image, and moving with lung sliding. They reflect changes in the air-fluid or tissue ratio in subpleural areas but are not a standalone diagnosis.

It is practically important to distinguish between single scattered B-lines, focal clustering in the symptom area, and a diffuse bilateral pattern. Focal B-lines near an irregular pleura and small subpleural consolidation often support a local inflammatory process. Diffuse B-lines require broad differential diagnosis and correlation with clinical findings, saturation, laboratory data, and other imaging methods.

Consolidation: Pneumonia or Atelectasis

Consolidation on ultrasound appears as a subpleural area of tissue-like echostructure replacing the normal air artifact. Important descriptors include location, shape, echogenicity, contours, pleural connection, presence of air or fluid bronchograms, and associated effusion.

Dynamic air bronchograms changing with respiration support inflammatory consolidation. More homogeneous consolidation with signs of volume reduction and less pronounced bronchogram dynamics may correspond to atelectasis. These signs should not be interpreted in isolation: mixed changes, such as pneumonia with areas of atelectasis or obstructive components, are possible in children.

Pleural Effusion and Complications

Ultrasound effectively identifies pleural fluid and helps distinguish free anechoic effusion from complex, heterogeneous, or septated content. In parapneumonic complications, it is important to describe fluid echogenicity, presence of septa, loculations, pleural thickening, and adjacent consolidation.

For the clinician, particularly significant in the report are signs affecting management: fluid accessibility for puncture or drainage, multicamerality, associated consolidation, signs of organization. Ultrasound is also convenient for guiding interventions if provided by local protocol and team competencies.

Minimum Reporting Protocol

The report should be reproducible. Ideally, it should first specify technical conditions and study volume, then describe each side by zones: pleural line, sliding, B-lines, consolidation, pleural fluid. A syndromic conclusion is then formulated, not just a list of artifacts.

• Pleura: line is smooth or irregular, sliding preserved or reduced, presence of thickening or interruption.
• B-lines: absent, single, focal multiple, or diffuse; specify side and zone.
• Consolidation: location, tissue-like nature, bronchograms, pleural connection.
• Effusion: presence, free or complex nature, septa, loculations.
• Interpretation: signs of peripheral pneumonic consolidation, atelectasis, pleural complication, or absence of ultrasound signs in accessible zones.

Limitations and Typical Errors

The main limitation of the method is the inability to assess pathology completely surrounded by aerated lung. Therefore, a negative ultrasound does not exclude pneumonia if the focus is central or not adjacent to the pleura. Further imaging is required if clinical findings do not match, in line with the ESPR 2025 approach to method selection.

Typical errors include considering B-lines as a diagnosis, failing to specify the extent of changes, confusing atelectasis and pneumonia without describing bronchograms, ignoring posterior areas in a supine child, and not describing the nature of pleural fluid. A standardized report reduces these risks and makes the study useful for pediatricians, pulmonologists, intensivists, and surgeons.