Chest radiograph interpretation in children — formative SAQs

SAQ 1 (10 marks)

A 3-year-old is brought to the emergency department with a 2-day history of fever and cough. A chest radiograph is performed in the department as an erect PA film. You are the paediatric registrar asked to interpret the film systematically before the formal radiologist's report is available. ^{[1] [3]}

1. Outline the structured technical-quality check you will perform before reading the lung fields, naming the five components and the finding that indicates adequacy in each. (5) ^{[1] [3]}
2. Describe the ABCDEFGH systematic review, stating what you look for in each zone. (3) ^[1]
3. State the named radiographic sign that localises an alveolar opacity to a particular lobe by the border it erases, and the sign that confirms the opacity is alveolar rather than pleural. (2) ^[1]

Model answer — SAQ 1

(1) Technical-quality check (5). I assess five components before reading the fields. First, projection: I confirm the film is PA, AP, or lateral, and that the projection matches the clinical question; a PA film in a cooperative child is the reference standard because the heart is least magnified. Second, position: erect or supine — an erect film best shows the apices, the costophrenic angles, and a small pleural effusion that layers dependently. Third, rotation: I check that the medial ends of the clavicles are symmetric and equidistant from the spinous processes; if they are not, the child is rotated and the heart and mediastinum are unreliable, because rotation widens the mediastinum and magnifies the heart. Fourth, inspiration: I confirm that at least nine posterior ribs cross the diaphragm at the midclavicular line; fewer indicates under-inflation, which crowds the ribs, elevates the diaphragm, and falsely enlarges the heart. Fifth, penetration: I confirm that the thoracic spine is just visible through the cardiac shadow and the intervertebral discs of the lower thoracic spine are seen; if the film is too white the mediastinal detail is lost, and if too black the lung detail is burned out. If the film fails any of these, I flag it as limited and interpret the key findings with the limitation stated. ^{[3] [1]}

(2) ABCDEFGH review (3). I review the film zone by zone. A — Airway: the trachea should be midline and the carina visible; deviation suggests a tension process, a mass, or volume loss. B — Bones: I trace every rib, the clavicles, and the spine for fractures or lytic or sclerotic lesions; in suspected non-accidental injury I look specifically for posterior rib fractures near the costovertebral junctions. C — Cardiac: the heart size and shape, the cardiothoracic ratio on a good film, and the silhouette sign to localise adjacent consolidation. D — Diaphragm: both hemidiaphragms should be sharp, the right slightly higher than the left, and the costophrenic angles clear. E — Effusions: I look in the dependent spaces and behind the heart, remembering a supine film hides free fluid. F — Fields: I assess the lung zones for aeration, consolidation, nodules, interstitial change, and air-trapping, comparing side with side. G — Gastric and gadgets: I identify every tube and line and confirm its position. H — Hilum and mediastinum: the hila should be symmetric with the left slightly higher, the mediastinal contour is traced, and the thymus is recognised as normal in the young child. ^[1]

(3) Named signs (2). The silhouette sign localises disease to a lobe by the border it erases: an opacity that obliterates the right heart border lies in the right middle lobe, and one that obliterates the diaphragm lies in the lower lobe, because a pathological density of soft-tissue attenuation adjacent to a structure of similar density destroys that structure's normal border. The air bronchogram — dark branching bronchi seen against the white background of consolidated alveoli — confirms that the opacity is alveolar and within the lung, rather than pleural or chest-wall in origin. ^[1]