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Objective: The purposes of this study were to determine the incidence of pneumorrhachis among patients with pneumomediastinum, determine whether its proportion correlates with the extent of pneumomediastinum, and ascertain its clinical relevance., Materials and Methods: The radiologic database was searched for CT reports between January 2009 and September 2013 containing the term "pneumomediastinum" or "mediastinal air." Scans were examined for pneumomediastinum, pneumorrhachis, pneumothorax, sternotomy, and distribution of pneumomediastinum. The age and sex of the patient and probable cause of the abnormality were recorded. Cases that might have had another cause were excluded., Results: The search yielded 422 CT scans. Among these, 242 instances of pneumomediastinum in 241 patients were found. Fifteen of these patients had pneumorrhachis. One was excluded because of recent traumatic spinal penetration. There was no significant difference in age or sex between patients with and those without pneumorrhachis. After application of the exclusion criteria, there were 14 cases of pneumorrhachis, yielding a proportion of 5.8%. Pneumorrhachis was observed more frequently in cases of the most severe grade (grade C) of pneumomediastinum; however, that relationship was not statistically significant (11 cases [8.2%]; p = 0.304). Pneumorrhachis was found significantly more frequently in patients with distribution of air in all three mediastinal compartments (13 cases, 16.2%, p < 0.001). Pneumorrhachis was overrepresented among subjects with spontaneous compared with those with secondary pneumomediastinum, although the trend did not reach statistical significance., Conclusion: Pneumorrhachis was present in 5.8% of patients. It is significantly more common in patients with the broadest distributions of mediastinal air and nonsignificantly more common in association with spontaneous as opposed to secondary pneumomediastinum. Pneumorrhachis in patients with pneumomediastinum is a generally benign, self-resolving condition.

Objective: The purpose of our study was to determine the necessity of fluoroscopic esophagography in patients with pneumomediastinum on CT but without CT findings of esophageal perforation., Materials and Methods: From January 1, 2006, through December 31, 2010, there were 4305 fluoroscopic esophagography examinations including 533 with CT identified from a search of our PACS. Patients with pneumomediastinum on CT who were subsequently referred for emergent fluoroscopic esophagography to exclude esophageal perforation were enrolled. Fluoroscopic esophagography examinations performed within 3 days of CT were included. Patients with a history of esophageal disease were excluded. As a result, 103 patients were enrolled in the study; patients were divided into groups on the basis of whether there was additional clinical history of esophageal damage (trauma group) or not (nontrauma group). Images were reviewed by two board-certified radiologists blinded to the clinical data and radiologic reports for the presence or absence of esophageal perforation. A positive result on CT was defined as esophageal injury or periesophageal infiltration that coexisted with periesophageal air. A positive fluoroscopic esophagography result was defined as oral contrast medium leakage from the esophagus., Results: Esophageal perforation was diagnosed in 15 of the 103 patients. The CT findings were significantly correlated with esophageal perforation (p < 0.001 in the trauma group, and p = 0.001 in the nontrauma group). The respective sensitivity and negative predictive value (NPV) of CT versus fluoroscopic esophagography in the trauma group were 100% versus 66.7% and 100% versus 87.9%; in the nontrauma group, the sensitivity and NPV were 100% for CT and fluoroscopic esophagography. Thus, the sensitivity and NPV of CT were either superior or equal to those of fluoroscopic esophagography., Conclusion: The results of our study suggest that performing fluoroscopic esophagography in patients with pneumomediastinum is unnecessary when CT is negative for esophageal perforation.

Objective: We report our experience with CT-guided percutaneous catheter drainage of loculated thoracic air collections in mechanically ventilated patients with acute lung injury or acute respiratory distress syndrome., Materials and Methods: Nine critically ill patients had 17 air collections (13 pneumothoraces, three pneumatoceles, one tension pneumomediastinum) that either developed despite the presence of standard surgical chest tubes or were in loculated sites that were difficult to access. All nine patients were ventilated mechanically for a clinical diagnosis of acute respiratory distress syndrome. Catheter size ranged from 7- to 28-French. Response was measured by imaging follow-up, ventilatory parameters, and clinical outcome., Results: On follow-up imaging studies, all 17 air collections were shown to have been evacuated successfully. Catheters remained in place for a mean of 11 days (range, 4-28 days). No major complications occurred. Sixteen air collections were treated successfully with CT-guided catheter placement alone; the remaining air collection, a pneumothorax, was treated with subsequent placement of a chest tube by the surgeon at the patient's bedside. No surgery was undertaken for the air collections. Improvement in gas exchange was documented by increase in the hypoxemia ratio (arterial oxygen pressure divided by the inspired fraction of oxygen) in seven of 12 drainages; the other drainages were accompanied either by no improvement or by deterioration. Eight (89%) of the nine patients eventually were extubated and discharged from the hospital. The ninth patient died., Conclusion: CT-guided percutaneous catheter drainage provided effective treatment for loculated thoracic air collections and obviated surgical intervention in these critically ill, high-surgical-risk patients.

Objective: The purpose of this study was to describe the CT features of infradiaphragmatic air that may develop in patients after mechanically assisted ventilation, its location, its pathway of transdiaphragmatic dissection, and its extension into the abdomen., Materials and Methods: We retrospectively evaluated six consecutive adult patients with pneumomediastinum associated with positive end-expiratory pressure therapy who developed intraabdominal air and were imaged with CT in our institution-between 1993 and 1995. Abdominal CT examinations were reviewed and correlated with the clinical findings, follow-up examinations, and exploratory laparotomies in four patients., Results: In four patients, air present in the anterior mediastinum (endothoracic fascia) was seen to extend into the anterior abdominal wall within the extraperitoneal space. In a fifth patient, the air was located extraperitoneally and intraperitoneally. In the remaining patient, air was present exclusively in the peritoneal cavity. In only two patients did we detect small amounts of air in the posterior retroperitoneum. In five patients, we also detected subcutaneous emphysema and/or air dissection into the muscle planes of the anterolateral abdominal wall., Conclusion: In patients on mechanically assisted ventilation, anterior mediastinal air can dissect through the diaphragm into the anterior abdominal extraperitoneal space. This anterior pathway of infradiaphragmatic extension of air can be erroneously diagnosed as intraperitoneal air, which may lead to unnecessary exploratory laparotomies. Also, anterior mediastinal air can enter the peritoneal cavity, particularly in patients with a history of median sternotomy.

The purpose of this study is to describe the radiologic manifestations of paraquat-induced pulmonary damage, with special emphasis on the sequential changes seen with this condition. Paraquat is a herbicide that has toxic effects on the lungs, liver, and kidneys. Progressive respiratory failure is a frequent cause of death. We analyzed retrospectively 42 patients with a history of paraquat ingestion and abnormal findings on chest radiographs. Radiographic changes during the first week after ingestion included diffuse consolidation (26/39), pneumomediastinum with or without pneumothorax (15/39), and cardiomegaly with widening of the superior mediastinum (8/39). Small cystic and linear shadows began to appear at the end of the first week and were the preponderant parenchymal abnormality after 2-4 weeks. Focal honeycombing was the major parenchymal abnormality after 4 weeks. High-resolution CT of the lung 9 months after paraquat exposure revealed localized fibrosis containing small cysts. Our study shows that the pulmonary manifestations of paraquat poisoning begin with air-space consolidation, which then leads to end-stage lung.

Pneumomediastinum as an iatrogenic complication of a diagnostic procedure is rare [1-7]. We report a case of pneumomediastinum following a double-contrast barium enema examination. With the increasing use of double-contrast barium studies, pneumomediastinum may be an important sign of rupture of the colon during this examination.

Traumatic injury to the tracheobronchial tree requires prompt, accurate diagnosis for optimum surgical treatment. The radiologist is in a pivotal position either to suggest this diagnosis or to initiate further investigation to establish it. Three cases of traumatic bronchial rupture illustrate the spectrum of radiologic findings and document the value of tomography in confirming this diagnosis.

Although most of the radiologic changes that have been described in transection or laceration of the trachea or main bronchi are nonspecific, they can be of diagnostic importance in the appropriate clinical setting. In order to reassess the significance of these findings, and to determine the presence of any other changes that might lead to a definitive diagnosis, we retrospectively reviewed the chest radiographs of nine patients who had tears or transection of the trachea and/or main bronchi as a result of blunt chest trauma. The diagnosis was proved by bronchoscopy in all patients and reconfirmed at surgery in five. The predominant findings on the chest radiographs were related to air leak and included subcutaneous emphysema (seven patients), pneumomediastinum (seven patients), pneumothorax (six patients), and air surrounding a bronchus in one patient. Upper thoracic fractures that involved the clavicles, scapula, sternum, and ribs were present in four patients. Abnormalities in the appearance of an endotracheal tube in two patients (overdistention of the cuff or extraluminal position of the tip), and the presence of the fallen lung sign (collapse of the lung toward the lateral chest wall) in two others provided specific evidence of tracheobronchial injury. We conclude that, although the major importance of the chest radiograph in patients with tracheobronchial transection may be to verify the existence of air leak, the presence of the fallen lung sign and endotracheal tube abnormalities is a reliable indication of airway injury.

It is classically taught that mediastinal air enters the abdomen posteriorly by dissection along vascular sheaths. Present studies in infants, children, and young adults demonstrate dissection of extrapleural air to the subdiaphragmatic extraperitoneal space between the sternocostal origins of the diaphragm. The presence of extrapleural air above and extraperitoneal air below the diaphragm clearly defines the anterior diaphragmatic attachments, producing a characteristic radiographic sign. Recognition of this sign permits precise localization of air collections above and below the diaphragm, implying subdiaphragmatic extension of extraalveolar air rather than retroperitoneal perforation of a hollow viscus. Since collections of both extrapleural and intrapleural air may collect in a subpulmonic location, the ability to distinguish one from another has definite implications regarding chest tube placement.

Four cases of paramediastinal pneumatocele were examined with CT to determine the location of the gas collection. Although such collections have previously been assumed to be in the pulmonary ligament, CT in these cases showed instead that the collection was in either the medial pleural space or in the posterior mediastinum.

The radiographic appearance of retrothymic pneumomediastinum is quite specific. The findings include elevation of the thymus away from other mediastinal structures with increased lucency beneath it, visualization of a radiodense line extending from the inferior pole of the thymus to the midportion of the heart, and tenting of the pericardium at the point of attachment of this line. This constellation of findings will aid in the differential diagnosis of medial anterior pneumothorax, pneumopericardium, and intrapulmonary cyst in the infant with air block. The paper details the mediastinal anatomy with special emphasis on a previously undescribed layer of connective tissue that accounts for this specific radiographic appearance.

Six neonates receiving assisted ventilation developed loculated posterior mediastinal gas collections. Relation to other mediastinal structures localizes these gas collections to the infraazygous region, and the midline location distinguishes infraazygous pneumomediastinum from air within the pulmonary ligaments. Infraazygous pneumomediastinum does not communicate freely with the anterior mediastinum, but often dissects cephalad and is frequently associated with pneumoperitoneum.

Fractures of the first and second ribs had a very low association with ruptured bronchus (2%) and ruptured aorta or brachiocephalic vessel (8%) in a series of 50 patients. Radiographic abnormalities indicative of ruptured bronchus include massive pneumothorax, pneumomediastinum, subcutaneous emphysema, and lobar or whole lung collapse which may fall to the dependent part of the thorax on erect views. Abnormalities pointing to a laceration of the aorta or one of the brachiocephalic vessels include widening of the superior mediastinum, shift of the trachea or nasogastric tube to the right, enlargement or indistinctness of the aortic knob, and widening of the right paraspinal line. One or more of these abnormalities indicates the need for thoracic aortography. In the absence of these abnormalities, aortography is not indicated solely by the presence of a first or second rib fracture on the chest radiograph.