Abstract
Pulmonary interstitial emphysema (PIE) is a rare condition most commonly encountered in mechanically ventilated patients, either infants or adults. This condition can also be diagnosed in blunt chest trauma or other conditions while performing Valsalva-like maneuvers and is often associated with pneumothorax and subcutaneous emphysema. We present the case of a patient with subtle PIE, subcutaneous emphysema and massive pneumomediastinum after protracted vomiting following a suicidal attempt by caustic ingestion. Radiologists should be aware of the potentially subtle Computed Tomography features of PIE in order to make the correct diagnosis and rule out other tracheobronchial and esophageal injuries.
Introduction
Pulmonary interstitial emphysema (PIE) is characterized by dissection of air from ruptured alveoli to the pulmonary interstitium. Usually, alveoli lacerate due to anomalous increase in intrapulmonary pression [1]. The condition is quite common in premature neonates undergoing mechanical ventilation for acute respiratory distress syndrome [2]; it is rarer in adults but again correlated to the need of ventilatory support, even if cases of PIE in spontaneous pneumomediastinum, severe asthma, chest trauma or hyperemesis gravidarum are described [3–6]. We present the case of a 36-year-old man who developed PIE after prolonged vomiting following a suicidal attempt by ingestion of a cleaning product and benzodiazepines.
Case report
A 36-year-old man was admitted to the Emergency Room after attempting suicide by ingestion of 20 ml of delorazepam and 700 ml of cleaning product in a creamy formula, the latter containing many ingredients, among which Sodium Alchyl Benzene Sulfonate, Alkyl Alcohol ethoxylates, Sodium Carbonate and Butyldiglycol which are ionic and non-ionic surfactants and are considered potentially harmful. The ingestion was followed by violent and repeated hyperemesis.
The patient underwent gastroesophageal endoscopy which excluded upper gastrointestinal tract perforation. Chest X-ray (not shown) was negative for pulmonary consolidations or pleural effusions.
After worsening of clinical conditions, the patient was transferred to the Intensive Care Unit. An urgent chest Computed Tomography (CT) was performed, showing subcutaneous laterocervical emphysema, massive pneumomediastinum, bilateral minimal pneumothorax and subtle diffuse interstitial emphysema; atelectasis of lower pulmonary lobes was also noted (Fig. 1).
CT at admission. A, B) Axial images showing pneumomediastinum (black arrows), pneumothorax (asterisk), interstitial emphysema (white arrows), atelectasis of lower lobes (curved arrows) and mediastinal shift towards the left side. C) Coronal Minimum Intensity projection reconstruction demonstrating air in peribronchial and perivascular spaces (white arrows). Subcutaneous laterocervical emphysema (curved arrows)
Citation: Imaging 15, 2; 10.1556/1647.2023.00166
Tracheobronchial injuries were excluded by radiology and endoscopy.
The patient was treated conservatively with gradual clinical improvement.
A chest CT performed four days later, before hospital discharge, showed improvement of the radiological picture with residual subtle pneumomediastinum and complete resolution of PIE and subcutaneous emphysema (Fig. 2).
CT after 4 days. Axial image showing spontaneous resolution of diffuse interstitial emphysema and residual minimal pneumomediastinum (arrow); almost complete re-expansion of right lower lobe and, partially, of the left lower lobe (curved arrows)
Citation: Imaging 15, 2; 10.1556/1647.2023.00166
Discussion
Pulmonary interstitial emphysema refers to a collection of air outside of the normal air space of the pulmonary alveoli, found instead in the pulmonary interstitium and lymphatics. It is the result of the development of positive pressure gradient between marginal alveoli and pulmonary interstitial tissue that leads to alveolar wall rupture and air leak in the interstitium; consequently, air takes the path of least resistance, extending to the hila with pneumomediastinum, to the subcutaneous tissues or to the subpleural region with pneumothorax [7–9]. At histology, it is characterized by cystic spaces with lack of epithelial lining [10]. Although more commonly encountered in mechanically ventilated infants with respiratory distress syndrome, it may also be occasionally detected in adults, mainly after ventilation, but also in association with severe coughing, bronchial asthma, trauma, interstitial lung diseases or other conditions associated with Valsalva maneuver [3, 5, 6, 8, 10].
Hyperemesis, either after intoxication (accidental or intentional), drug-related or during pregnancy has also been reported as a possible cause of PIE [3]. We present this case suggesting that protracted vomiting causing repeated and forced Valsalva maneuver could be the etiology of PIE.
The diagnosis of PIE is usually based on radiological examinations, with CT being more sensitive than X-rays: PIE will appear as air-density areas (often linear or lenticular in shape) tracking along the bronchovascular bundles, the visceral pleura, and/or interstitial septa and is often associated with pneumomediastinum, as in our case and in another recently described in literature [11]. Especially when PIE is encountered in severe blunt trauma, CT plays a crucial role also in excluding potential tracheobronchial and/or esophageal injuries.
Pulmonary interstitial emphysema, pneumomediastinum and subcutaneous emphysema often run a benign course, especially in young otherwise healthy subjects, and can be managed conservatively. However, they can also be complicated by potentially detrimental sequelae, especially in those patients with pre-existing pulmonary diseases, among which tension pneumothorax, tension pneumomediastinum or compression atelectasis of adjacent healthy lung as encountered in our case [12].
Conclusion
Although most commonly encountered in an evocative clinical (mechanically ventilated patients), radiologists should be aware of other conditions which may represent risk factors for PIE. It is important to have knowledge the typical CT features of PIE and carefully look for its signs. When the diagnosis is established, a high degree of vigilance must be maintained for any potentially serious complication.
Authors' contributions
All authors contributed to the study conception and design. Definition of intellectual content, literature research, data collection and analysis were performed by Elena Belloni, Federica Lucev and Davide Stoppa. The first draft of the manuscript was written by Elena Belloni and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
Funding sources
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Conflict of interests
The authors declare that they have no declarations of interest.
Ethical statement
The manuscript respects all ethical principles and maintains the anonymity of patient data.
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