March 2026 - Meconium Aspiration Syndrome

Case Summary

This case highlights the role of lung point-of-care ultrasound (POCUS) in the diagnosis of meconium aspiration syndrome (MAS) in a term newborn presenting with severe respiratory distress and pulmonary hypertension. Lung ultrasound demonstrated widespread, unevenly distributed consolidations with pleural line abnormalities and interstitial involvement, findings characteristic of MAS. In neonates with respiratory distress, lung ultrasound allows rapid bedside evaluation of lung aeration patterns and can help distinguish between common etiologies such as respiratory distress syndrome (RDS), transient tachypnea of the newborn (TTN), and MAS. Early use of POCUS can therefore improve diagnostic accuracy and guide clinical management.

Clinical Situation

This infant was delivered by emergency Caesarean section due to an abnormal fetal heart rate tracing. Meconium-stained amniotic fluid was noted at delivery. At birth, the newborn was hypotonic, apneic, and had a heart rate below 100 beats per minute. The infant required immediate resuscitation and was rapidly intubated for respiratory support. Shortly after intubation, the endotracheal tube became obstructed by thick secretions and had to be removed. A trial of non-invasive respiratory support was attempted; however, the infant quickly developed severe hypercapnia, with a CO₂ level reaching 104 mmHg, as well as persistent hypoxemia with oxygen saturations remaining below target despite an FiO₂ of 100%. The infant was therefore reintubated at approximately two hours of life prior to transfer to a tertiary neonatal intensive care unit. Following admission, lung point-of-care ultrasound was performed and demonstrated findings highly suggestive of meconium aspiration syndrome. The infant subsequently received surfactant therapy. Targeted neonatal echocardiography was also performed and demonstrated signs of pulmonary hypertension. Inhaled nitric oxide therapy was therefore initiated. Respiratory status progressively improved over the following days. Inhaled nitric oxide was discontinued on day of life 3, and the infant was extubated the same day to bubble CPAP. The infant was weaned from bubble CPAP on day of life 10 and required low-flow nasal cannula oxygen support for an additional period of 6 days. By day of life 16, respiratory status had stabilized and the infant was successfully weaned to room air. The infant was discharged home in good clinical condition on day of life 20.

POCUS Examination

Lung point-of-care ultrasound was performed at the bedside using a GE Venue Go ultrasound system equipped with a high-frequency linear “hockey stick” transducer (8–18 MHz). The lungs were systematically examined using a six-zone anterior scanning protocol. Each hemithorax was evaluated in three anterior regions to allow a rapid assessment of lung aeration patterns. Lung ultrasound demonstrated multifocal areas of consolidation unevenly distributed throughout the lungs, with greater involvement of dependent regions. The interface between consolidated and normally aerated lung tissue appeared irregular, producing a characteristic shred (fractal) sign (A), a classic sonographic feature of lung consolidation. Within the consolidated regions, dynamic air bronchograms were visible. Additional pleural line abnormalities were also noted, including pleural line thickening overlying the affected areas.

In the consolidated zones, A-lines disappeared and were replaced by dense coalescent B-lines, consistent with alveolar–interstitial involvement. In surrounding lung regions, multiple B-lines were present, while some localized A-lines persisted, reflecting patchy and heterogeneous lung aeration, a pattern typical of meconium aspiration syndrome (B). A small pleural effusion was also identified, suggesting significant pulmonary inflammation and exudative lung injury (A). Overall, the lung ultrasound findings were highly suggestive of severe meconium aspiration syndrome.

Teaching Points

Lung ultrasound is a valuable bedside tool for evaluating neonatal respiratory distress. Typical lung ultrasound findings in meconium aspiration syndrome include: 

• Multifocal and unevenly distributed lung consolidations

• Shred (or fractal) sign at the interface between consolidated and aerated lung and air bronchograms

• Extensive pleural line abnormalities (thickening, discontinuity, blurring)

• Dense or coalescent B-lines reflecting alveolar-interstitial involvement

• Heterogenous (Patchy) distribution with spared areas showing localized A-lines

• Possible pleural effusion in severe cases 

Compared with chest radiography, lung ultrasound provides a dynamic and radiation-free assessment of lung pathology, enabling clinicians to monitor disease evolution and response to therapy.

Conclusion

This case reinforces the utility of lung ultrasound in the evaluation of neonatal respiratory distress, demonstrating how characteristic sonographic patterns can support the identification and monitoring of a wide range of neonatal lung diseases, including meconium aspiration syndrome.