Characteristic Chest X-Ray Findings in Term Neonates with Persistent Respiratory Distress
While chest X-ray (CXR) has traditionally been used for neonatal respiratory imaging, lung ultrasound is now the preferred first-line imaging modality due to superior diagnostic accuracy and absence of radiation exposure. 1, 2 However, when CXR is performed, specific patterns help distinguish between the major causes of respiratory distress in term neonates.
Important Clinical Context
The question asks about CXR findings, but current evidence strongly favors lung ultrasound as the primary imaging modality for neonatal respiratory distress. 1, 2 Lung ultrasound has demonstrated equal or superior diagnostic accuracy compared to CXR while eliminating radiation exposure, and it provides more specific pathognomonic findings for differential diagnosis. 1, 3
CXR Findings by Diagnosis
Transient Tachypnea of the Newborn (TTN)
- Fluid in lung fissures is a characteristic finding on CXR in TTN, representing delayed clearance of fetal lung fluid. 4
- Bilateral perihilar streaking or prominent vascular markings may be present. 5
- Hyperinflation with flattened diaphragms can occur. 5
- Important caveat: CXR findings in TTN are relatively nonspecific compared to ultrasound, which shows the pathognomonic pattern of bilateral confluent B-lines in dependent areas with normal superior fields. 6, 1
Respiratory Distress Syndrome (RDS)
- Diffuse bilateral ground-glass opacification throughout all lung fields without spared areas. 7, 5
- Air bronchograms may be visible. 5
- Low lung volumes with poor aeration. 5
- Critical distinction: Unlike TTN, RDS shows uniform involvement without regional variation. 7
Pneumonia
- Focal or patchy consolidations. 6, 5
- Pleural effusions may be present. 6
- Distribution can be unilateral or bilateral depending on etiology. 5
Meconium Aspiration Syndrome (MAS)
- Patchy, asymmetric infiltrates. 5
- Hyperinflation alternating with areas of atelectasis. 5
- Dynamic pattern: The radiographic appearance changes as meconium plugs migrate during mechanical ventilation. 6
Critical Limitations of CXR
CXR exposes neonates to ionizing radiation with potential long-term risks including increased cancer risk, particularly in premature infants. 2, 8 Studies demonstrate that routine use of lung ultrasound reduces CXR utilization by approximately 29% (from 100% to 71.2% of patients) and decreases radiation dose per infant from 5.54 to 4.47 µGy. 8
CXR has poor inter-observer reliability for neonatal respiratory diseases. 3 For bronchopulmonary dysplasia prediction, CXR shows Cohen's kappa values of only 0.19-0.41, indicating poor agreement between readers. 3 In contrast, lung ultrasound demonstrates excellent reliability with Cohen's kappa ≥0.9 for RDS diagnosis and ≥0.82 for BPD prediction. 3
Recommended Imaging Approach
Lung ultrasound should be the first-line imaging modality for term neonates with respiratory distress. 1, 2 Reserve CXR for:
- Cases where ultrasound findings are unclear or inconclusive. 9
- Suspected pneumothorax when ultrasound is not immediately available (though ultrasound is more sensitive). 6
- Evaluation for congenital malformations of the chest or airways. 5
Integration of clinical features with imaging findings is essential for accurate diagnosis in most cases. 5 The specific timing of symptom onset (immediate at birth versus within 2 hours), gestational age, and response to oxygen help narrow the differential diagnosis alongside imaging patterns.