CASE 17863 Published on 30.08.2022
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Pulmonary interstitial emphysema after lung transplantation: an early sign of chronic lung allograft rejection.

Section

Chest imaging

Case Type

Clinical Cases

Authors

Lucas Walgrave, Walter De Wever

University Hospital Leuven, campus Gasthuisberg, Herestraat 49, 3000 Leuven, Belgium

Connected authors
Patient

25 years, male

Categories
Area of Interest Respiratory system, Thorax ; Imaging Technique CT, CT-High Resolution
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Clinical History

We present a case of a 25-year-old male who was hospitalized due to respiratory deterioration several years after bilateral lung transplantation. He had a history of neonatal bronchiolitis obliterans and recurrent infections, leading to severe bronchiectasis and organizing pneumonia, warranting lung transplantation.

Imaging Findings

Computed tomography (CT) of the chest showed extensive multifocal linear and cystic air spaces distributed in the subpleural, perifissural, septal and peribronchovascular spaces, with ground glass attenuation of the background parenchyma (Fig. 1). These findings were markedly progressive compared to the CT scans performed two and three years prior (Fig. 2, 3). Consecutive CT performed three months after hospital admission showed the formation of large cysts/bullae in the subpleural and perifissural spaces along with extensive parenchymal destruction, volume loss and fibrosis (Fig. 4).

Discussion

Pulmonary interstitial emphysema (PIE) is a rare condition defined by air dissecting within the interstitial tissues of the lung. This creates cystic air spaces histologically characterized by a surrounding inflammatory and fibrotic reaction [1].

The Macklin effect describes air from these ruptured alveoli spreading along the bronchovascular bundles to the pulmonary hilum and subpleural space, causing pneumomediastinum and pneumothorax respectively [2–6]. 

PIE is a well-known condition in the pre-term neonate, most often occurring in cases of surfactant deficiency and mechanical ventilation [7, 8]. In this discussion we focus on PIE in adults, often occurring as an acute sequela of barotrauma. It has also been documented in various interstitial lung diseases (ILD), severe asthma, drug inhalation, chronic graft-versus-host disease, and post-lung transplantation. The spectrum of associated ILDs is broad, ranging from idiopathic pulmonary fibrosis to hypersensitivity pneumonitis and connective tissue disease-associated ILDs [5, 6, 9–22]. 

PIE seen in the first thirty days after lung transplantation is a sign of dehiscence of the bronchial anastomosis [23, 24]. Slowly progressive, refractory PIE reflects underlying structural parenchymal damage due to chronic rejection and remodeling of the transplanted lung, causing destruction of the secondary pulmonary lobule. PIE may be seen before the diagnosis of CLAD (chronic lung allograft dysfunction) can be made clinically, and before other radiological signs of BOS (bronchiolitis obliterans syndrome) and RAS (restrictive allograft syndrome) may be present [25, 26].

PIE can be seen on plain radiograph as linear or cystic radiolucencies converging towards the hilum. However, it is best characterized on CT, appearing as elongated pockets of air in the subpleural, septal and peribronchovascular spaces. PIE is accentuated on expiratory scans, due to the increased contrast to the adjacent parenchyma [27, 28]. PIE may appear as sharply and regularly delineated streaks, or as more irregular and branching emphysema in the pulmonary interstitium. PIE can mimic classic centrilobular and paraseptal emphysema; the distribution along the bronchovascular bundles can help differentiate these entities [6, 28].

Prognosis of PIE is variable, depending on etiology, comorbidities, and treatment [18]. Management is often centered around the causative pathology. In cases of barotrauma, supplemental oxygen can be administered to reduce hypoxia and increase the reabsorption rate of the air. Pneumomediastinum and pneumothorax may resolve without treatment, or require chest tube thoracostomy [29].

In conclusion, the detection of slow onset, progressive and refractory PIE after lung transplantation is an important clue to the early diagnosis of CLAD.

Differential Diagnosis List
Pulmonary interstitial emphysema signifying chronic lung allograft rejection.
Pulmonary interstitial emphysema in thoracic air leak syndrome.
Cystic lung diseases
Centrilobular/paraseptal emphysema
Final Diagnosis
Pulmonary interstitial emphysema signifying chronic lung allograft rejection.
Case information
URL: https://eurorad.org/case/17863
DOI: 10.35100/eurorad/case.17863
ISSN: 1563-4086
License

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Figure 1

Chest CT, axial view, performed at the time of hospital admission

There is extensive pulmonary interstitial emphysema (PIE) in the perifissural and subpleural spaces (black arrows) and in the
There is extensive pulmonary interstitial emphysema (PIE) in the perifissural and subpleural spaces (black arrows) and in the peribronchial and perivascular spaces (white arrows). There is ground glass attenuation of the background parenchyma due to mixed type CLAD.
Figure 2

Chest CT, axial view, performed two years prior

Findings are similar but less pronounced compared to figure 1. PIE can be clearly seen along the lung fissures (black arrows)
Findings are similar but less pronounced compared to figure 1. PIE can be clearly seen along the lung fissures (black arrows) and in the peribronchiolar and perivascular spaces (white arrows). The ground glass attenuation of the lung parenchyma is more subtle.
Figure 3

Chest CT, axial view, performed three years prior

Discrete PIE is seen along the lung fissures (black arrows), along the pulmonary vessels and interspersed throughout the norm
Discrete PIE is seen along the lung fissures (black arrows), along the pulmonary vessels and interspersed throughout the normal parenchyma (white arrows). Windowing is slightly adjusted to enhance contrast and better depict the subtle findings.
Figure 4

Sagittal reconstruction of chest CT, performed three months after hospital admission

There is progressive PIE with formation of extensive subpleural and perifissural cysts/bullae (black arrows). Furthermore, th
There is progressive PIE with formation of extensive subpleural and perifissural cysts/bullae (black arrows). Furthermore, there is marked architectural destruction of lung parenchyma with volume loss and fibrosis (white arrows). There is ground glass attenuation of the background parenchyma due to mixed type CLAD.