November 2026 - Lung POCUS to differentiate atelectasis from pleural effusion

Case November 2026 – Lung Point-of-Care Ultrasound to differentiate atelectasis from suspected pleural effusion in an extremely preterm infant

Authors:

Dr. Luis Quiel - Neonatal-Perinatal Medicine Fellow at McGill University
Dr. Nina Nouraeyan - Neonatologist at the Jewish General Hospital; Department of Pediatrics of McGill University

Posted: November 4, 2026

Case Summary

This case highlights the role of lung POCUS in differentiating pleural from parenchymal abnormalities in an extremely preterm infant that developed progressive right-sided pulmonary opacification on day of life 4. Findings supported pulmonary atelectasis rather than pleural fluid accumulation as the likely explanation for the progressive radiographic opacification. Ventilatory management was subsequently optimized by increasing positive end-expiratory pressure (PEEP) to promote alveolar recruitment. POCUS was useful in refining the differential diagnosis and informing targeted ventilatory management in extremely preterm neonates.

Clinical Situation

An extremely preterm infant was delivered at 23+5 weeks of gestation to a 37-year-old mother (G3P1A1) with no significant past medical or surgical history. Her obstetric history included a previous term spontaneous vaginal delivery and a spontaneous pregnancy loss at 17 weeks of gestation. During the current pregnancy, a cervical cerclage was placed at 13 weeks because of cervical insufficiency. At 22+6 weeks, the mother was transferred to a tertiary care centre following mild abdominal pain, vaginal bleeding, and bulging membranes. During hospitalization, she received antibiotics and completed a course of antenatal corticosteroids. Subsequent cervical dilation to 3 cm and a positive AmniSure test raised concern for PPROM. Elevated maternal white blood cell count and C-reactive protein raised concern for intra-amniotic infection. Following cerclage removal, purulent material was observed in the vaginal canal, further supporting the clinical suspicion of infection. Vaginal delivery was initially attempted; however, fetal distress associated with bradycardia prompted an emergency cesarean delivery. The infant was born weighing 760 g and initially required positive-pressure ventilation followed by continuous positive airway pressure (CPAP). Due to worsening respiratory retractions and recurrent apneic episodes, endotracheal intubation was performed in the delivery room. Following admission to the neonatal intensive care unit (NICU), the infant was placed on assist-control volume-guarantee ventilation (AC-VG) with relatively low ventilatory requirements. Umbilical venous and arterial catheters were inserted, exogenous surfactant was administered and antibiotics were started. On DOL 4, serial chest radiographs demonstrated evolving right-sided pulmonary opacities. Given the presence of a UVC and concern for possible catheter displacement, catheter-associated pleural effusion was considered. Although the UVC tip projected within the inferior vena cava on radiography, concerns regarding catheter migration or related complications prompted withdrawal of the catheter to a peripheral position. The progressive radiographic abnormalities and diagnostic uncertainty prompted bedside lung POCUS to further characterize the pulmonary findings and guide clinical management.

Radiography Findings

Initial

The initial chest X-ray obtained on the morning of DOL 4 demonstrated increased pulmonary opacities predominantly involving the right mid-to-lower lung zones, with additional diffuse ground-glass opacities involving the contralateral lung. The endotracheal tube tip was approximately 3 mm above the carina, and the UVC tip projected within the inferior vena cava.

Repeat radiography with progression of opacity

A repeat chest X-ray obtained later that afternoon demonstrated progression to a more homogeneous right-sided pulmonary opacity, particularly involving the mid-to-lower lung fields. This raised concern for pleural effusion, although pulmonary atelectasis remained an important differential diagnosis.

Lung POCUS

Bedside lung POCUS was performed to investigate the progressive right-sided pulmonary opacification and evaluate for suspected pleural effusion in the context of a recently placed UVC. The examination demonstrated no sonographic evidence of pleural effusion. Areas of pulmonary atelectasis were identified in the dependant lung regions (R2 and R3), corresponding to the distribution of the radiographic abnormalities.

Coalecent B-lines with thickened pleural line.

Irregular pleural line (shred sign) with subpleural consolidations and static air bronchograms.

Again, irregular pleural line (shred sign) with subpleural consolidations and static air bronchograms.

A subsequent chest radiograph demonstrated improved pulmonary aeration and partial resolution of the right-sided atelectasis. No repeat lung ultrasound was performed following the ventilatory adjustment.

Serial chest Xray showing progression after lung POCUS guided intervention

Teaching points

Lung POCUS can differentiate pleural effusion from pulmonary atelectasis when chest radiography is inconclusive. Both conditions may present as homogeneous pulmonary opacification on chest radiography. Lung ultrasound provides additional bedside information by identifying pleural fluid and characterizing peripheral pulmonary abnormalities, including subpleural consolidation and atelectatic changes.
Progressive unilateral pulmonary opacification in an intubated extremely preterm infant requires a systematic diagnostic approach. The differential diagnosis includes pulmonary atelectasis, endotracheal tube malposition, pleural effusion, pulmonary consolidation, and catheter-related complications. Integrating clinical assessment with radiography and lung POCUS can help narrow the differential diagnosis and identify the most appropriate intervention.
Lung POCUS is particularly valuable when catheter-associated pleural effusion is suspected. Umbilical venous catheter migration or extravasation may lead to fluid accumulation within the pleural cavity. Bedside lung ultrasound can rapidly evaluate for pleural fluid and help distinguish this complication from pulmonary parenchymal abnormalities. A negative pleural ultrasound does not independently establish catheter safety or exclude other catheter-related complications.
Identifying pulmonary atelectasis can support individualized ventilatory management. In mechanically ventilated neonates, pulmonary atelectasis may contribute to impaired gas exchange and heterogeneous lung aeration. Identifying areas of collapse may support consideration of lung recruitment strategies, including cautious PEEP optimization, while accounting for the risks of overdistension and hemodynamic compromise.
Lung POCUS and chest radiography provide complementary information during clinical assessment. In this case, lung POCUS clarified the underlying pathology and informed the ventilatory strategy, while subsequent chest radiography documented improved pulmonary aeration following PEEP adjustment. Serial multimodal assessment can help clinicians evaluate evolving pulmonary abnormalities and treatment response.

Conclusion

This case demonstrates the clinical utility of lung POCUS in an extremely preterm infant with progressive unilateral pulmonary opacification and suspected pleural effusion. By demonstrating the absence of pleural fluid and identifying areas of pulmonary atelectasis, bedside ultrasound helped clarify the differential diagnosis and informed a targeted ventilatory strategy focused on improving lung recruitment. Following PEEP optimization, repeat chest radiography demonstrated improved pulmonary aeration and partial resolution of the right-sided collapse. Integrating lung POCUS into the bedside assessment of critically ill neonates may facilitate timely diagnostic clarification, support individualized ventilatory management, and complement conventional radiographic evaluation when pulmonary findings are inconclusive.