Chest X-Rays: 16 Subtle But Key Findings You Need to Know
Lars Grimm, MD, MHS | August 2, 2017
The chest radiograph is one of the views most commonly ordered by clinicians, and it is frequently first viewed by non-radiologists. Although many disease processes are obvious at first glance on chest radiographs, clinicians must be careful not to miss more subtle findings.
This image shows a solitary pulmonary nodule (circle) in the left midlung.
Image courtesy of Lars Grimm, MD, MHS.
Sarcoidosis
Bilateral hilar lymphadenopathy ( arrows) and right paratracheal lymphadenopathy is present on pulmonary radiographs in up to 80% of patients with sarcoidosis. [1] Granulomas, pulmonary infiltrates, and fibrosis may also be seen. [2] In more advanced disease (stage 4), fibrosis, hilar retraction, decreased lung volumes, and honeycombing may develop. [2,3]
Sarcoidosis is a multisystem granulomatous disease of unknown etiology that classically presents with pulmonary (90% of cases), eye, or skin lesions in young adults (age, 20-50 years).[1,4,5] The lymph nodes, liver, and other tissues may also be involved. In the United States, the disease is more common and more severe in blacks than in whites, and women are affected more often than men. [3-5]
Image courtesy of Lars Grimm, MD, MHS.
Pulmonary Hypertension
In patients with pulmonary hypertension, the most common findings on chest radiographs are enlarged pulmonary arteries [6,7] ( arrow) that taper distally (peripheral pruning). [7] A dilated right ventricle with a decreased retrosternal space may also be seen on lateral images. [6,7]
Pulmonary hypertension develops as a result of increased pulmonary artery pressure and vascular resistance. [6] Primary pulmonary hypertension usually affects young women and is a disease of unknown etiology. Secondary pulmonary artery hypertension can occur from precapillary (eg, left-to-right shunt), capillary (eg, veno-occlusive disease), or postcapillary (eg, chronic lung disease) causes. Certain medications and illicit drugs may also cause pulmonary hypertension. [6]
Image courtesy of Lars Grimm, MD, MHS.
Pancoast Tumors
Pancoast tumors are pulmonary neoplasms located in the superior sulcus of the lung. [8,9] On chest radiographs, these tumors may appear as a unilateral apical opacity ( arrow) or an apical asymmetry. [8,9] Local rib destruction, particularly of the first rib, may also be present. Lordotic chest views may be helpful to clarify a suspected lesion. [8,9]
Pancoast tumors are predominantly non–small cell carcinomas, particularly of squamous cell histology. [8] They characteristically cross the pleural barrier to invade the chest wall, brachial plexus, and superior sympathetic ganglion (resulting in Horner syndrome). [8,9]
Image courtesy of Lars Grimm, MD, MHS.
Asbestos-Related Disease
Disease caused by inhalation of asbestos fibers (typically from industrial or occupational exposures) produces chest radiographic findings of bilateral calcified pleural plaques over the diaphragmatic, peripheral, or mediastinal pleura (arrows). [10] Noncalcified pleural plaques are not readily appreciated on chest radiographs, but these lesions may be fully displayed on computed tomography (CT) scans. [10]
Progression of asbestos-related disease to involve the lung parenchyma is known as asbestosis. This predominantly affects the interstitial compartment of the lung and manifests as increased interstitial markings, coarse parenchymal bands, rounded atelectasis, and parenchymal distortion on chest radiographs. [10] The appearance of pleural effusion—particularly if it is associated with an enlarging pleural mass and localized pain—indicates the development of a mesothelioma. [10]
Image courtesy of Medscape.
Primary Pleural Neoplasms
Localized fibrous tumor of the pleura (LFTP) (or solitary FTP) and malignant mesothelioma are primary pleural neoplasms. [11]
Localized fibrous tumor of the pleura
LFTP is generally a benign neoplasm of the pleura that is not associated with asbestos exposure. This tumor is usually detected incidentally on chest radiographs, and typical findings include a well-circumscribed, homogeneous soft-tissue mass that is closely related to the pleura. [11] The lesion may be found anywhere along the lung periphery ( shown, upper left hemithorax), pulmonary fissures, mediastinum, or diaphragm. Large lesions may be confused with lobar consolidation.
Image courtesy of Lars Grimm, MD, MHS.
Mesothelioma
Unilateral irregular, nodular, and diffuse pleural thickening is the classic finding on chest radiographs in patients with malignant mesothelioma. [10,12] The pleural thickening may be either plaquelike or nodular. Pleural effusions may obscure the pleura, making it difficult to evaluate the thickness; however, the fissures may also become thickened with an irregular contour, which can aid in the diagnosis. The presence of calcified pleural plaques indicates previous asbestos exposure, which is a risk factor for the development of mesothelioma. [10,12]
The image demonstrates thickening of the left lateral pleura ( blue arrow) with lobulation and effusion ( orange arrow). Other potential causes of unilateral pleural thickening are empyema, trauma, postoperative scarring, and metastatic disease.
Image courtesy of Lars Grimm, MD, MHS.
Pulmonary Aspergillosis
Pulmonary aspergillosis is a fungal infection caused by the Aspergillus species, most commonly A fumigatus. There are four distinct forms of pulmonary aspergillosis [13,14]: allergic bronchopulmonary aspergillosis (ABPA), aspergilloma, chronic necrotizing aspergillosis (CNPA), and angioinvasive aspergillosis.
Chest radiographic findings of ABPA include lobar infiltrates, [13,14] perihilar "glovelike" tubular shadows representing mucus-filled bronchiectasis, [13,14] and tram-line bronchial walls due to edema. [14] The characteristic features of an aspergilloma are a round mass with an adjacent crescent-shaped air space ( arrow). [13,14] The fungal ball itself may be freely mobile and move when the patient changes position. [13,14]
Chronic necrotizing aspergillosis may appear as segmental areas of consolidation, predominantly in the upper lobes, that progress toward cavitation. [14] Angioinvasive aspergillosis most commonly appears as patchy areas of consolidation with solitary or multiple nodules and peripheral wedge-shaped lesions due to hemorrhagic infarcts. [13,14]
Image courtesy of Lars Grimm, MD, MHS.
Solitary Pulmonary Nodule
A solitary pulmonary nodule is defined as a single discrete pulmonary opacity that is surrounded by normal lung and is not associated with adenopathy, atelectasis, or pleural effusion.[15,16] The list of potential conditions in the differential diagnosis is extensive and broadly includes benign and malignant neoplasms, infections, noninfectious granulomas, developmental lesions, vascular lesions, and other systemic processes. Although the exact etiology of a nodule may not be discernable on a chest radiograph, failure to detect a lesion and failure to obtain appropriate follow-up can lead to significant patient morbidity and mortality.
Key radiographic features to identify are the size, location, growth rate, and margin characteristics of the nodule, as well as the presence and pattern of cavitation and calcification. Factors that favor malignancy are growth over time; large size; an irregular, lobulated, or spiculated margin; and an upper lobe location. [15,16] It may be easy to miss a lesion that overlaps the ribs or clavicles.
This image is from a patient with a solitary pulmonary nodule ( arrow) that has been stable for 2 years and is therefore considered benign.
Image courtesy of Lars Grimm, MD, MHS.
Tracheal Stenosis
Tracheal stenosis is a narrowing of the trachea that may result from chronic inflammatory disease, neoplasm, and trauma, as well as iatrogenic causes and extrinsic compression from lesions such as an intrathoracic goiter. [17]
On chest radiographs, the trachea and mainstem bronchi can readily be assessed for changes in caliber. The radiograph may also provide clues as to the cause of stenosis, such as tracheal deviation or a widened mediastinum, or other potential etiologies for shortness of breath, such as an aspirated foreign body.
The image is from a patient with a known thoracic malignancy with tracheal narrowing ( arrow) from metastatic disease.
Image courtesy of Lars Grimm, MD, MHS.
Cavitary Lung Lesions
This cavitary lesion with an air-fluid level ( arrow) was concerning for neoplasm. Cavitary lung lesions on chest radiographs can be the result of an abscess, tuberculosis, carcinoma, granulomatosis with polyangiitis, metastatic cancer, or septic emboli. [18] Key features to identify are the cavity's size, wall thickness, and location (this may provide clues as to the potential etiology of the lesion), [18] as well as the presence of any air-fluid levels. Lateral radiographs may be needed to help confirm the location of the lesion(s).
Abscesses typically have thick walls and may have air-fluid levels. In general, metastatic lesions have thin-walled cavities, but their appearance may vary. Lesions from granulomatosis with polyangiitis and septic emboli are typically smaller.
Image courtesy of Lars Grimm, MD, MHS.
Osteomyelitis
Osteomyelitis is an infection of the bone and bone marrow that may be classified as acute, subacute, or chronic. [19] It may be easily missed on chest radiographs if careful attention is not paid to the bones in addition to the lung fields.
Typical findings of acute or subacute osteomyelitis on plain radiographs are soft-tissue swelling, periosteal reaction, cortical irregularity, and demineralization. [19] In chronic osteomyelitis, there is an elevated periosteum and thick, irregular, sclerotic bone that is interspersed with radiolucencies.
The image is from a patient with chronic osteomyelitis of the left scapula. Note the associated bony expansion, sclerosis, and periosteal reaction (arrow).
Image courtesy of Lars Grimm, MD, MHS.
Cancerous Bone Lesions
Primary bone cancer and metastasis to bones may be evident on chest radiographs. [20,21] Bone lesions may be sclerotic, lytic, or mixed, which can give clues to their etiology. [21]Common malignancies that give rise to sclerotic metastasis are prostate cancer, breast cancer, and lymphoma [21-24]; those that result in lytic metastasis are renal cell cancer, [22,24]multiple myeloma, [21,24] and thyroid cancer. [22,24]
This close-up chest radiograph reveals a lytic expansile left fourth rib lesion ( arrow) due to multiple myeloma.
Image courtesy of Lars Grimm, MD, MHS.
Compression Fractures
Compression fractures of the thoracic spine occur whenever the spinal column is subjected to forces that exceed its strength and stability. [25] They may be first detected on chest radiographs by carefully evaluating the vertebral bodies.
Typical findings on a plain radiograph for anterior compression fractures include cortical impaction, loss of vertical height, buckling of the anterior cortex, trabecular compaction, and endplate fracture. [25] Lateral radiographs may provide better views of the spinal architecture.
This lateral chest radiograph demonstrates kyphosis of the thoracic spine with compression fractures of at least two upper thoracic vertebral bodies (arrows).
Image courtesy of Lars Grimm, MD, MHS.
Hyperlucent Lung
Unilateral hyperlucent lung may be the result of Swyer-James syndrome, pneumothorax, obstructive emphysema, or pulmonary embolism. [26] Hyperlucency is typically the result of alveolar distention (air retention) and/or reduced arterial flow. [26-28]
Swyer-James syndrome is a manifestation of postinfectious obliterative bronchiolitis that is found in children. [27,28] On chest radiographs, the ipsilateral lung is hyperlucent and overexpanded ( shown, left lung), compared with the contralateral lung, which is smaller ( shown, right lung). [27]
In this image, note the hyperexpansion of the left lung field as well as the hypertranslucency at its periphery compared with the right lung field.
Image courtesy of Lars Grimm, MD, MHS.
Pneumoperitoneum
Pneumoperitoneum refers to the presence of air within the peritoneal cavity. [29] This may be easily seen on upright chest radiographs as a lucency beneath either diaphragm ( arrows). The presence of air under the diaphragm does not always imply a perforation and is commonly seen after surgery, as was the case in the image shown. [29]
Typically, benign pneumoperitoneum due to surgery resolves after 3-6 days. [29] Colonic or gastric gas may mimic free air under the left hemidiaphragm and, therefore, close attention is essential to ensure there is only a thin layer of diaphragm between the abdominal and thoracic contents rather than gastric or colonic wall.
Image courtesy of Lars Grimm, MD, MHS.
Enlarged Cardiac Silhouette
An enlarged cardiac contour may be due to multiple causes, including cardiomegaly, pericardial effusion, a pericardial cyst, or an aneurysm. [30]
In a pericardial effusion, there is an abnormal amount of fluid and/or an abnormal character to the fluid in the pericardial space. [30] The heart has a globular contour ( shown), but confirmation via ultrasonography or CT scanning may be necessary. [30,31] Pericardial effusions may be transudative, due to obstruction of the lymphatic channels, or exudative, due to infection, inflammation, or malignancy. [30] Effusions are common after cardiac surgery and most often resolve after 1 month. Pericardiocentesis is a safe and effective treatment option.