Pulmonary Interstitial Emphysema Workup

Updated: Nov 09, 2017
  • Author: Abhay J Bhatt, MD, MBBS; Chief Editor: Muhammad Aslam, MD  more...
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Workup

Approach Considerations

 

 

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Radiography

Pulmonary interstitial emphysema (PIE) is a radiographic and pathologic diagnosis. However, obtain blood gases in affected infants to ensure adequate gas exchange.

The classic radiologic appearance of PIE often provides a clear diagnosis. PIE is best visualized in the anteroposterior supine projection. This condition has two basic radiographic appearances, linear or cystlike radiolucencies, although both types often appear together.

Linear radiolucencies are coarse and nonbranching, measure from 3 to 8 mm, and vary in width but rarely exceed 2 mm. Cystlike radiolucencies are small, ranging from 1 to 4 mm in diameter; although generally round, they may also appear oval or slightly lobulated.

The disorganized, haphazard distribution of PIE in localized areas is unlike the anatomically organized pattern of the air bronchogram. The air bronchogram is a classic radiographic sign of respiratory distress syndrome (RDS), which should not be confused with PIE.

In RDS, long, smooth, branching, linear radiolucencies decrease in caliber from the hilum and frequently disappear at the lung periphery. PIE should be suspected when coarse radiolucencies appear in the lung periphery or when the lucencies do not branch in a pattern consistent with the normal bronchial tree.

In some infants receiving mechanical ventilation therapy, the distended airways and alveoli have a somewhat similar radiographic appearance to that of PIE. Over time, this either progresses to a classic radiographic picture of PIE or resolves very rapidly as the ventilator settings are lowered.

Rarely, PIE can be misinterpreted as a normally aerated lung surrounded by exudate, as in an aspiration syndrome or pulmonary edema. [26]

The first radiograph below shows a right-sided pneumothorax and PIE. Interstitial air prevents collapse of the underlying lung by a tension pneumothorax. In such cases, extreme caution is required during drainage of the pneumothorax to avoid perforation of the underlying lung.

This radiograph shows pneumothorax and pulmonary i This radiograph shows pneumothorax and pulmonary interstitial emphysema (PIE) on the right side. Interstitial air prevents collapse of the underlying lung by a tension pneumothorax. In such cases, extreme caution is required during drainage of a pneumothorax to avoid perforation of the underlying lung.
This radiograph, obtained from a 1-day-old prematu This radiograph, obtained from a 1-day-old premature infant at 24 weeks' gestation, shows bilateral pulmonary interstitial emphysema (PIE). Linear radiolucencies extending up to the lung periphery are visible.
This radiograph, obtained from a premature infant This radiograph, obtained from a premature infant at 26 weeks' gestation, shows characteristic radiographic changes of pulmonary interstitial emphysema (PIE) of the right lung.

Computed tomography (CT) scanning of the chest can be a helpful diagnostic tool if doubt about the diagnosis remains, particularly in persistent cases and if surgical interventions are being considered. A round or linear soft-tissue component seen in the wall of or within the air-containing spaces is a key to making the correct diagnosis. [27]  In addition, the presence of subpleural PIE, in which there is an interstitial air collection in the subpleural region of the lungs excluding the bronchovascular bundle, on CT scan suggests single or multiple alveolar rupture(s) as an origin of pneumomediastinal air. [1]  

See the Medscape Drugs & Diseases articles Imaging in Pulmonary Interstitial Emphysema, Respiratory Distress Syndrome Imaging,  and Imaging in Bronchopulmonary Dysplasia for more information on these topics.

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Histologic Findings

The histology of pulmonary interstitial emphysema (PIE) has been well described by Plenat et al. [13]  Interstitial slits are preferentially located in the perivenous topography.

Occasionally, the peribronchial arterial or arteriolar sheaths are involved. Air dissects through a plane just next to the arterial or arteriolar face, opposite the bronchus, which is pushed into adjoining parenchyma. Most often, the bronchoarterial solidarity is respected.

Seldom, air can dissect arterioles and bronchioles and isolate them from the adjacent lobules. On the periphery of interstitial slits, the small vessels are compressed but never ruptured, whereas the collagen fibers are constantly broken and squeezed together.

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