CRITICAL CHEST RADIOGRAPHSCANT-MISS DIAGNOSESBY DR. MOHAMED R. YOUSSEF ER RESIDENT,QUALITY COORDINATOR MGHSOURCE :-MEDSCAPE.COM
Chest radiographs are the most common radiologic tests performed in hospitals and emergency departments. Although radiologists are responsible for the final interpretation of studies, many chest radiographs are first viewed by non-radiologists. All physicians should be able to quickly and accurately identify a wide number of critical findings to help identify patients who need subsequent emergent care.
This image is of an individual with a majorpneumoperitoneum showing the outline of the liver and spleen
A pneumothorax occurs when air fills the space between the parietal and visceral pleura of the lungs. A primary spontaneous pneumothorax occurs without any underlying lung disease and in the absence of an inciting event, while a secondary spontaneous pneumothorax occurs in people with underlying parenchymal lung disease (eg, chronic obstructive pulmonary disease, pulmonary fibrosis). On a chest radiograph, a pneumothorax may be identified by a discrete shadowed line beyond which no lung markings are present (arrows). They most commonly occur in the lung apices, which are the least dependent part of the lung. However, on supine radiographs, pneumothoraces may be subpulmonic or anteromedial in location. Comparison between inspiratory and expiratory films may aid in detection.
A tension pneumothorax is the accumulation of air under pressure in the pleural space. It develops when injured tissue creates a one-way valve for air to enter, but not leave, the pleural space. Diagnosis should be made on clinical grounds by contralateral tracheal deviation, ipsilateral hyperresonance to percussion, ipsilateral decreased breath sounds, distended neck veins, and hypoperfusion. The typical radiographic findings are ipsilateral lung collapse (white arrow) with widened intercostal spaces and contralateral mediastinal deviation (red arrow). With a left hemithorax, the left hemidiaphram may be depressed, but the liver prevents this from developing on the right side.
Pneumomediastinum is free air in the mediastinal structures. It most commonly occurs following trauma or iatrogenic injury to the esophagus or adjacent alveoli. On chest radiography, free air may outline anatomic structures. Common findings are a thin line of radiolucency that outlines the cardiac silhouette (white arrow), vertically oriented streaks of air in the mediastinum, a double bronchial wall sign, or lucency around the right pulmonary artery, the "ring around the artery" sign. Air is most easily detected retrosternally on lateral chest radiographs. Air is fixed in a pneumomediastinum and does not rise to the highest point
Airway foreign bodies are most often found in pediatric patients. The most common site of foreign bodies is the right mainstem bronchus due to its posterior location, shallow angle to the trachea, and wide diameter. The density of the ingested item will determine whether it can be directly identified on radiographs. Indirect signs of ingestion include focal overinflation if there is partial obstruction or atelectasis if there is more complete obstruction. The image shown demonstrates a radiopaque earring backing (arrow) lodged in the right mainstem bronchus of a child.
Pneumoperitoneum refers to air within the peritoneal cavity, most commonly from perforation of an abdominal viscus. Air will accumulate in the least dependent portion of the abdominal cavity. During upright chest radiographs, air will separate the liver, spleen, and intestines from the diaphragm producing dark crescents (arrows shown). To ensure adequate air migration, patients should be kept upright for at least 5 minutes before the image is taken. Sometimes, a double-wall, or Riglers,sign can be seen which refers to internal and external air outlining the intestinal wall.
Green arrows = luminal surface;white arrows = peritoneal surface
Pericardial effusions result from the accumulation of fluid within the pericardial space. The classic finding on a chest radiograph is an enlarged cardiac silhouette, the so-called water-bottle heart. However, if the fluid accumulates rapidly, then minimal cardiomegaly may be present. Other potential findings include pleural effusion and rarely pericardial calcifications.
Acute respiratory distress syndrome is defined as acute onset, a PaO2 to FIO2 of 200 mm Hg or less, bilateral chest radiograph infiltrates, and a pulmonary arterial wedge pressure of 18 mm Hg or less or no clinical signs of left atrial hypertension. The most common findings on chest radiographs are bilateral, predominately peripheral, asymmetric consolidations with air bronchograms (arrows shown). Septal lines and pleural effusions are uncommon findings. Early findings during the exudative phase are bilateral consolidations that obscure the pulmonary vascular markings. These opacities extend to more extensive diffuse consolidations that are typically asymmetric. In the subsequent fibrotic stage, a diffuse interstitial appearance may develop. Most radiographic abnormalities begin to resolve after 10-14 days if the patient survives.
Four main criteria for ARDS: Acute onset Chest X-Ray: Bilateral diffuse infiltrates of the lungs No cardiovascular lesion No evidence of left atrial hypertension: PaO2/FiO2 ratio equal to or less than 200 mmHg.
Thoracic aortic aneurysms are defined as a greater than 50% aneurysmal dilatation of the normal ascending thoracic aorta, aortic arch, or descending thoracic aorta. The descending thoracic aorta is the most common site. On chest radiographs, the most common findings are a widening of the mediastinal silhouette (white arrow), enlargement of the aortic knob, and tracheal displacement (red arrow). Other radiographic findings include a double-opacity appearance to the aorta representing true and false lumens, localized bulges along the aortic contour, and a disparity in the caliber of the descending and ascending aorta
Diaphragmatic hernias are caused when a defect in the diaphragmatic wall allows for the herniation of abdominal contents into the thoracic cavity. The majority of tears are on the left side. On chest radiographs, asymmetry of a hemidiaphragm or changing diaphragmatic levels may be present (arrow). Gas-filled organs or a nasogastric tube within the thoracic cavity will confirm the diagnosis. Solid abdominal organs will appear as mushroom- shaped homogeneous opacities. Potential misdiagnosis can occur in the case of diaphragmatic paralysis or after lung reduction surgery
Congestive heart failure is a clinical syndrome in which the heart fails to adequately pump blood to metabolizing tissues. A number of typical findings may be present on a chest radiograph. With cardiomegaly, the cardiothoracic ratio increases to greater than 50% on a posterior-anterior chest radiograph (white lines). Kerley B lines may be present on the lung periphery that are the result of interlobular septal thickening. Accumulated pleural fluid may blunt the costophrenic angles (red arrow) or cause large pleural effusions. Pulmonary edema may cause bilateral increased lung markings in a perihilar, or bat-winged, distribution. Increased pulmonary capillary pressure causes the upper lobe vessels to be equal or larger in caliber than the lower lobe vessels, referred to as cephalization.
Aspiration pneumonia is an infectious process caused by aspirated oropharyngeal flora or gastric contents. It is differentiated from aspiration pneumonitis, which is caused by direct chemical insult from the aspirated material. Typical findings on chest radiographs are bilateral opacities in the middle or lower lung zones (shown). In the acute phase, transient infiltrates or lobar consolidation may be present, while chronic aspiration may appear as a solidified mass
Although the initial placement of an endotracheal tube is evaluated with bilateral auscultation and usually a carbon dioxide detector, a chest radiograph is routinely performed for confirmation. Endotracheal tubes have a radiopaque strip impregnated along one side to aid in evaluation. The tip of the tube should be 2-6 cm (double-headed arrow) above the carina (angled lines). At this position, the tip will provide adequate ventilation when the tube is shifted during neck flexion or extension. If the tube is positioned too deeply, then there may be selective intubation of only one lung, which can lead to complete atelectatic collapse of the contralateral lung.
A hydropneumothorax refers to the presence of both air and fluid within the pleural space. It may develop after esophageal rupture (shown), trauma, infection with a gas-forming organism, development of a bronchopleural fistula, or iatrogenic after surgery. An upright chest radiograph will typically show a horizontal air-fluid level that extends across the whole length of the hemithorax (arrow). For an air-fluid level to be present, there must be both air and fluid within the pleural space.
A left ventricular aneurysm is an uncommon complication after a myocardial infarction, in which weakened myocardial tissue creates a distinctive outpouching of the left ventricle. On chest radiographs, the total heart size will be enlarged with a prominent bulging of the left heart border. On lateral radiographs, there will be distortion of the lateral heart profile, either anterior or posterior (shown) depending on the region of outpouching. In some cases, a rim of calcification may be present outlining the aneurysm itself. Image courtesy of Dr. Eugene C. Lin.