Main Air Leak Syndromes
Spontaneous pneumothorax and pneumomediastinum in infants require careful analysis of radiographs, as classic patterns typical of adult patients may be absent.
- Pneumothorax. Diagnosing pneumothorax in critically ill neonates is complicated by the fact that radiographs are most often performed with the patient in the supine position. In this position, free air rises and accumulates over the anterior surface of the lung. Because of this, the classic visceral pleural line may not be visible. Key radiographic markers include total hyperlucency of the affected hemithorax, unnaturally sharp contours of the mediastinum and diaphragm dome, and the formation of a pathologically deep costophrenic sulcus (the so-called deep sulcus sign).
- Pneumomediastinum. The accumulation of air in the mediastinum classically outlines the contours of the thymus, making it clearly visible on the radiograph. In severe cases, gas can spread cranially, penetrating the soft tissues of the neck.
- Pneumopericardium. Characterized by the presence of an air halo that completely surrounds the cardiac silhouette, separating it from surrounding structures.
Pleural Effusions
If the neonate has no hydrops fetalis, the most common cause of fluid accumulation in the pleural cavity is chylothorax. The exact etiology of this condition is not fully understood, but the primary theory is late maturation of the thoracic duct.
- Antenatal period. Pathological fluid accumulation is usually detected during routine fetal ultrasound. If the effusion volume is large, there is a risk of pulmonary hypoplasia. In such cases, fetal intrauterine thoracentesis may be used.
- Postnatal imaging. After birth, the diagnosis is confirmed by chest radiography, which visualizes a characteristic opacification corresponding to pleural effusion (bilateral chylothorax is common).
- Characteristics of the aspirate. Aspiration of pleural fluid reveals a high lymphocyte count. It is important to remember that initially the fluid is clear; it acquires its characteristic "milky" appearance exclusively after the infant begins receiving enteral nutrition containing fats.
The prognosis for chylothorax is favorable in most cases, with complete resolution, though the condition may require multiple therapeutic aspirations.
Genetic Surfactant Disorders
Abnormalities in surfactant function and metabolism caused by genetic defects can lead to severe interstitial lung disease.
Genetic variants and clinical presentation:
- Surfactant protein B (SpB) and ATP-binding cassette transporter A3 (ABCA3) gene mutations have an autosomal recessive inheritance pattern. Respiratory symptoms with these mutations manifest immediately after birth.
- Surfactant protein C (SpC) gene mutations are most commonly inherited in an autosomal dominant manner and can remain asymptomatic for a long time, presenting clinically in later infancy.
Imaging methods:
- Radiography: initial stages reveal diffuse hazy opacification of the lung fields. As the disease progresses, a pronounced reticular pattern develops.
- Computed tomography (CT): the pattern directly depends on the histopathological picture. Pulmonary alveolar proteinosis (PAP) manifests as a crazy paving pattern. Cellular nonspecific interstitial pneumonia (NSIP) or chronic pneumonitis of infancy on CT show a combination of ground-glass opacification, interlobular septal thickening, and cystic changes.
Another distinct entity is pulmonary interstitial glycogenosis (PIG), which occurs in both preterm and term infants shortly after birth. On CT, it mimics surfactant deficiency (ground-glass opacification and parenchymal cysts are visualized). The definitive diagnosis is established only after pathomorphological examination of lung tissue.
Lines and Tubes
Analysis of a newborn's radiograph necessarily includes assessing the correct position of invasive devices.
- Endotracheal tube (ETT). The tip of the tube is extremely mobile and can shift significantly with any movements of the infant's head and neck. The correct position of the ETT must be assessed strictly taking into account the position of the child's head at the time of the radiograph.
- Umbilical arterial catheter. Inserted via the umbilical artery, it passes into the internal and common iliac arteries, reaching the aorta. To avoid thrombosis, the tip should not be located at the level of origin of major visceral branches. Two positions are acceptable: "High" (at the level of vertebral bodies Th6–Th9) and "Low" (below the L3 body).
- Umbilical venous catheter. It runs upward toward the liver, enters the left portal vein, passes through the ductus venosus, and empties into the inferior vena cava (IVC). The ideal tip position is strictly at the junction of the inferior vena cava and the right atrium.
- Central venous catheters (CVCs). Regardless of access site (internal jugular vein or upper extremity PICC lines), catheter tips should be positioned in the superior vena cava.
Briefly: answers to topical questions
What pathological conditions and iatrogenic factors cause pneumothorax in newborns?
Causes of pneumothorax in newborns include spontaneous conditions, complications of diseases, and medical interventions.
Pathological conditions include:
- Spontaneous pneumothorax — occurs independently and causes respiratory distress.
- Meconium aspiration syndrome — accompanied by the development of air leaks.
Iatrogenic factors include:
- Positive pressure ventilation — pneumothorax is a direct complication of this respiratory support.
- Anastomotic leak (leak) — following surgical repair of esophageal atresia may manifest with a radiographic picture of tension pneumothorax.
What conservative and surgical treatments are used for refractory congenital chylothorax?
Fluid evacuation methods are used to treat congenital chylothorax, while specific therapy for refractory forms is not described in the materials.
Available methods include:
- Intrauterine drainage — used in the antenatal period for large effusion volumes to prevent pulmonary hypoplasia.
- Repeated paracentesis (aspirations) — used in the postnatal period, as the condition often requires repeated removal of accumulating fluid until complete resolution.
Remember the difference in umbilical catheter pathways: The arterial catheter goes down (into the iliacs) and then up into the aorta; the venous catheter goes straight up (into the liver, through the duct into the inferior vena cava).
Class and exam questions
Why might a pneumothorax in infants be occult on a standard chest radiograph?
Radiographs in critically ill neonates are performed in the supine position. Because of this, free gas accumulates not in the apices (as in the upright position), but over the anterior surface of the lung, causing only the deep sulcus sign and generalized hyperlucency.
Is clear pleural fluid a reason to rule out chylothorax?
No. The effusion in chylothorax contains many lymphocytes, but acquires its classic milky appearance exclusively after the infant starts enteral feeding with fat-containing formulas.
How to differentiate SpB mutations from SpC mutations based on the clinical presentation?
Surfactant protein B (SpB) mutations present with respiratory symptoms immediately after birth (autosomal recessive), whereas SpC mutations (autosomal dominant) may not manifest until later in infancy.
What else to study on this topic
- Pathomorphological criteria for the diagnosis of pulmonary interstitial glycogenosis (PIG).
- Technique and indications for in utero fetal pleural drainage in chylothorax.
- Differential CT diagnosis of "crazy-paving" and "ground-glass opacity" patterns in infants.
- Assessment of endotracheal tube migration during flexion and extension of the newborn's neck.
- Radiographic anatomical landmarks for determining the Th6-Th9 and L3 levels.
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