Pediatric Thoracic and Cardiovascular Imaging
Pediatric chest imaging begins with the differences between the neonatal and adult chest. The thymus is normally large and can mimic a mass: the spinnaker sail sign, wave sign, and notched contour are normal. A trap is overdiagnosing mediastinal widening or pneumonia in a neonate; assess whether the trachea and vessels are displaced before calling a thymic shadow abnormal. In respiratory distress, first check lung volumes, position of tubes and lines, and symmetry. Transient tachypnea of the newborn shows normal or increased volumes with perihilar streaking and fluid in the fissures. Respiratory distress syndrome shows low volumes, reticulogranular opacity, and air bronchograms, often requiring surfactant. Meconium aspiration shows hyperinflation and patchy asymmetric opacities; congenital diaphragmatic hernia shows bowel in the chest with mediastinal shift.
Know congenital lung malformations: CPAM (cystic, usually a single lobe, normal systemic venous drainage), bronchopulmonary sequestration (systemic arterial supply, often left lower lobe), congenital lobar overinflation, and bronchial atresia. For cardiac disease, divide lesions into cyanotic and acyanotic and note ductal dependency. Tetralogy of Fallot has a boot-shaped heart with decreased pulmonary vascularity; transposition shows a narrow pedicle and egg-on-side silhouette; total anomalous pulmonary venous return can show a snowman. Vascular rings compress the trachea and esophagus and are evaluated with barium swallow, CT, or MRI.
Worked rule: In a neonate with respiratory distress and a scaphoid abdomen, suspect congenital diaphragmatic hernia and place a nasogastric tube before ventilation; the frontal radiograph showing bowel loops in the left hemithorax with shift confirms the diagnosis. Avoid mask positive-pressure ventilation when CDH is suspected.