Occult pneumomediastinum after blunt chest trauma: worrisome finding yet good clinical outcome: A Case Report

Abstract

Occult pneumomediastinum refers to the presence of mediastinal air when there was no evidence of it on a chest X-ray. It is of importance to exclude aerodigestive tract injuries in order to avoid unnecessary endoscopic or surgical procedures. Multi-detector computed tomography is the first-line non-invasive imaging method which is readily available for the diagnosis and exclusion of possible aerodigestive tract injuries. Moreover, the administration of oral contrast, which can be easily tolerated by patients, may augment the diagnostic efficiency. We present a young patient with occult pneumomediastinum after blunt chest trauma who presented with chiefly esophageal symptoms suggestive of esophageal perforation. CT findings and management are discussed.

Keywords

Introduction

Pneumomediastinum after penetrating trauma is often associated with either an aerodigestive or a thoracic injury which warrants immediate surgical intervention.¹ However, the presentation of pneumomediastinum after blunt trauma is rare and the management less clear. Because of its low incidence, the diagnosis can be easily missed. Although esophageal injuries are rare manifesting in <0.1% to 1.5% of patients with blunt chest trauma, mortality rate as 19% has been reported in those cases.²
Radiologic evaluation is important for the diagnosis and management at this prospect. In this regard, multidetector computed tomography (MDCT) plays a key role in the setting of thoracic blunt trauma.³ However, its controversial utility and benefits in trauma patients, oral contrast administration in proper patients can aid in diagnosis by narrowing the differentials in terms of esophageal perforation. In this case report, we present a patient with occult pneumomediastinum after falling down on the road in whom water-soluble oral contrast administration ruled out esophageal perforation thus eliminated the need for additional examinations.

Case Presentation

A 24-year-old man admitted to the emergency department with the complaint of difficulty in swallowing. His symptoms began after the patient slipped and fell on an icy road and landed on his chest three hours before the presentation. He had no past history of medical record. Written consent for the publication from the patient was obtained.
On physical exam, heart rate was 85bpm, blood pressure 110/70mmHg, respiratory rate 18 breaths per minute, and temperature 37.3°C. Oxygen saturation of 99% on room air was detected by pulse oximetry. A slight tenderness on the sternum was present on palpation. No crepitus in the chest and neck area which indicated subcutaneous emphysema were observed. The auscultation of the lungs was clear. Heart sounds were regular with normal S1 and S2. No murmurs or extra sounds were detected. The abdominal exam was unremarkable.
Routine laboratory exams were of no significance. Normal sinus rhythm and no evidence of myocardial ischemia were seen on the electrocardiogram. Then, a chest X-ray was ordered in which no significant gas outlining mediastinal structures, pneumothorax or subcutaneous emphysema was detected. The lung parenchyma fields were normal. Chest CT with intravenous contrast which is performed due to the persistence of his symptoms revealed free mediastinal air consistent with the diagnosis of a pneumomediastinum (Figure 1 a-b) without any other findings especially any emphysema or bullae. As the chief complain of the patient was difficulty in swallowing which was regarded as an esophageal symptom, consultant radiologist suggested a second scan with oral water-soluble contrast to rule out esophageal perforation. As there was no discernable oral contrast extravasation into the mediastinum (Figure 1 cd), further examination with esophagoscopy was dismissed and the patient was followed up. Bronchoscopy was also opted out as there was no discernible disruption of the tracheobronchial tree. The patient was managed as an inpatient conservatively with analgesia (acetaminophen), prophylactic antibiotics for 7 days (first piperacillin-tazobactam intravenously in case of mediastinitis, followed by amoxicillin-clavulanate orally) and anti-constipation therapy in order to prevent any positive pressure. He was taught to avoid maneuvers that increased chest pressure (forced expiration or Valsalva maneuver). The pneumomediastinum resolved completely on 48-hour control chest CT and the patient was discharged after symptomatic resolution without any complications by the 7th day of his admission.

Discussion

The thoracic injury which can be caused either by blunt or penetrating trauma is associated with considerable morbidity and mortality due to the relation with the injuries of the tracheobronchial tree, esophagus or vascular structures. Approximately 25% of blunt traumatic causalities are a direct result of thoracic injury.¹ In a study that evaluated blunt trauma patients with CT scans and the rate of occult pneumomediastinum was found to be 6% which implies that it is not a rare occurrence.² In patients with pneumomediastinum, blunt trauma is the mostly faced injury mechanism and may co-occur with severe blunt thoracic and cervical trauma up to 10% of patients. Highspeed motor vehicle accidents account for the major reason for blunt trauma in those patients.¹ The Macklin effect is the most common cause of pneumomediastinum in the setting of blunt trauma. It is the outcome of rupture of terminal alveoli afflicted by increased intrathoracic pressure and consequent dissection of air through peribronchial and perivascular fascial sheaths, finally into the mediastinum.⁴ In patients with blunt trauma, pneumomediastinum is regarded as an ominous finding because it can arise from anatomical sources such as head and neck, submandibular space, retropharyngeal space, and even retroperitoneal space or pelvis. It may not originate automatically and not necessarily in the intra-thoracic aerodigestive tract. Traumatic pneumomediastinum is sourced by tracheobronchial or esophageal tears in up to 10% of patients.⁵ Although esophageal injuries are rare manifesting in <0.1% to 1.5% of patients, mortality rate as 19% has been reported in those cases.² At this point, it is of utmost importance to evaluate patients for possible esophageal injuries to prompt surgical intervention.
In the presence of pneumomediastinum, aerodigestive tract injury must be ruled out which may result in a fatality. Historically, this required definitive identification of injuries with esophagogram, esophagogastroduodenoscopy, and bronchoscopy.⁶ These procedures for evaluation can be poorly tolerated to some extent, and although the risks of iatrogenic injury are low, they are not zero. Accessibility to endoscopic techniques, patient preparation, and sedoanalgesia may be challenging. In our patient, bronchoscopy was opted out as there was no discernible disruption of the tracheobronchial tree. The consultant gastroenterologist favored esophagoscopy in the first place to rule out esophageal perforation. After no water-soluble iodine contrast extravasation into mediastinum was demonstrated, this choice was also opted out and the patient was managed conservatively without any complications. The pneumomediastinum resolved completely on 48-hour control chest CT and the patient was discharged after symptomatic resolution. It is reported that occult pneumomediastinum resolved in average 3 hours after the initial exam.²
CT exams are more sensitive to detect free mediastinal air than chest X-ray and the expanding use of CT scan for first assessment plays a role not only in diagnosing mediastinal air but also in the management of trauma patients, in particular, those with blunt chest trauma.^3,6 Another feature expected from CT is the ability to detect possible esophageal injuries with high sensitivity. Oral contrast media administration can enhance its ability to rule out such injuries. There are plenty of studies concerning the oral contrast administration in blunt trauma patients mostly in abdominopelvic injuries. The majority of studies conclude that CT without oral contrast material is adequate for depiction intraabdominal injuries that required surgical repair thus obviate its administration.^7-8 However, these studies were related to abdominal trauma and to the extent of our knowledge, utilization of oral contrast in thoracic trauma patients has not been investigated. Although we excluded esophageal perforation by using water-soluble oral contrast medium in our patient, the lack of solid studies concerning contrast media administration in this patient group prevents us to make any concrete recommendation.

Conclusion

Occult pneumomediastinum in the setting of blunt trauma is a rare occurrence where any presence of aerodigestive tract injury warrants surgical intervention. In patients highly suggestive of such injuries, esophagoscopy or bronchoscopy have the major role for excluding aerodigestive perforation, while a thorough CT scan can obviate these strenuous examinations. The efficacy of CT scan in ruling out a significant digestive tract injury may be enhanced by oral contrast administration in the targeted patients yet further studies with large patient groups are warranted to draw solid conclusions.

Declarations

References

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