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Persistent Localized PIE Can Occur in the Absence of Mechanical Ventilation

September 30, 2009
Written by: , Filed in: Chest Radiology
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Background to the Case Study
A 33-week (estimated gestational age), 2017-gram female infant developed respiratory distress (RD) after birth. Initial chest X-ray (CXR) showed diffuse hazy opacity; 12-hour CXR revealed granular opacities consistent with surfactant deficiency syndrome, which was associated with linear left perihilar lucencies and consistent with pulmonary interstitial emphysema (PIE). In addition, an intraparenchymal retrocardiac focus of gas was identified.

Post intubation film showed a left pneumothorax. Chest tube was placed and surfactant administered. Infant was extubated 1 day after birth.

Follow-up CXR showed persistent RD syndrome (RDS) and left cystic lucencies. On physical examination, infant had coarse breath sounds, diminished on the left; respiratory rate was 78 breaths per minute; and she had O2 saturation of 93% at 0.71 per minute.

CT showed pneumomediastinum associated with linear and cystic lucencies of left lung causing contralateral mediastinal shift. Gas surrounded central bronchovascular bundles.

On day of life 20, follow-up CT showed cystic lung lesions had increased and was associated with increased mass effect and mediastinal shift. Patient did well, was weaned from oxygen, and was discharged at 35 days of life. At 7 months, CT showed resolution of interstitial and cystic lucencies.

Conclusions
Premature infants aged >=26 weeks gestation have developed terminal air sacs, some alveoli and type II pneumocytes. Hyaline membrane or surfactant deficiency disease causes atelectasis, hypoventilation, and hypoxemia. Symptoms begin before 6 hours of life and peak between 24 and 48 hours.

With development of synthetic surfactant, radiographic appearance of RDS changes. Now, instead of low volume lungs, homogenous opacity with lucent air-bronchograms and asymmetric opacities are identified. Surfactant decreases alveolar surface tension, allowing alveoli to expand with less effort.

Air leaks including PIE, pneumomediastinum, pneumopericardium, pneumothorax, and pneumoperitoneum may occur.

When the alveolar basement membrane ruptures, air moves into the interstitium.

Pulmonary Interstitial Emphysema is seen radiographically as small lucent dots within interstitium, vascular sheath, and lymphatics. Here, the misplaced air holds up traffic, impairing gas exchange, if focal, causing mass effect.

Focal cystic lucencies in the lung of a young infant can mimic the CXR appearance of congenital cystic adenomatoid malformation, congenital lobar emphysema, and bronchogenic cyst, among others.

While management of Pulmonary Interstitial Emphysema is medical, treatment of congenital lung masses is surgical.

This report illustrates a case of PIE that developed in the absence of mechanical ventilation and persisted following the one day of ventilator treatment.

The authors note that local persistent PIE should be added to differential diagnosis of cystic lung mass and can be distinguish when serial CXR are reviewed.

Patients with congenital lung lesions have evidence of a mass at birth, while the child who develops PIE would be expected to have an initial film that did not have cysts or evidence of mass effect.

Author: Sosamma T. Methratta, MD

Reference:
Berk DR, Varich LJ. Localized Persistent Pulmonary Interstitial Emphysema in a Preterm Infant in the Absence of Mechanical Ventilation. Pediatr Radiol; 2005; 35 (December): 1243-1245

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