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Parasites

Parasites are defined as organisms that live in or on another living organism, obtain part or all of their organic nutriment from that organism, and cause some degree of damage to their host. Parasitic infestations occur mainly in tropical and subtropical regions. Pulmonary disease secondary to parasites in North America and Europe is seen in individuals who traveled to endemic areas and in recent immigrants. Parasites…

Viruses

Viruses are the most common cause of respiratory infection and may result in rhinitis, pharyngitis, laryngotracheitis, bronchitis, bronchiolitis, and, less commonly, pneumonia. Most viral pneumonias in immunocompetent adults are due to influenza viruses; other common viral etiologies include respiratory syncytial virus (RSV) and adenovirus. Immunocompromised hosts are particularly susceptible to pneumonias caused by cytomegalovirus (CMV) and herpesviruses. Risk factors associated with increased incidence and severity of…

Fungal Infections

Etiology Fungal infections of the chest can be divided into two groups based on pathogenesis. The first group is composed of endemic fungi, including Histoplasma capsulatum, Coccidioides immitis, Blastomyces dermatitidis, and Cryptococcus gattii , and the second group is composed of opportunistic fungi, including Aspergillus, Candida, Cryptococcus neoformans, and Zygomycetes. Prevalence and Epidemiology The endemic fungi typically reside in the soil of certain regions, which is…

Nontuberculous (Atypical) Mycobacterial Infection

A variety of nontuberculous mycobacteria (NTMB) can cause pulmonary infections, with important differences in epidemiology, microbiology, host response, and treatment options across the various species. The severity of an infection caused by NTMB is largely determined by the immune status of the individual and whether coexisting disease is present. More complex manifestations of NTMB are now recognized, such as the overlapping pathology of hypersensitivity pneumonitis and…

Pulmonary Tuberculosis

Overview Etiology, Prevalence, and Epidemiology Tuberculosis (TB) is a chronic recurrent contagious infection caused by Mycobacterium tuberculosis. M. tuberculosis is an aerobic, nonmotile, non–spore-forming rod that is highly resistant to drying, acid, and alcohol. It is transmitted person to person via droplet nuclei containing the organism and spread mainly by coughing. The contagiousness of a patient with TB increases with greater extent of disease, the presence…

Bacterial Pneumonia

Etiology, Prevalence, and Epidemiology Pneumonia and influenza represent the eighth leading cause of mortality in the United States, with an estimated 1.3 million hospital admissions yearly attributable to pneumonia in patients older than 65 years. Although pneumonia affects all ages, increased morbidity and mortality are seen at the extremes of age (very young and very old). Pneumonia is broadly divided into infection acquired in the community…

Congenital Malformations of the Pulmonary Vessels in Adults

Congenital malformations of the pulmonary vessels include absence or interruption, abnormal sizes, origins, or courses, and abnormal connections of the pulmonary arteries or veins. These abnormalities commonly accompany other congenital pulmonary or cardiac disorders but can occur in isolation. Although some malformations have no clinical significance and may be an incidental finding at imaging, others may have important consequences. For example, pulmonary hypertension may occur in…

Airway and Parenchymal Anomalies

Congenital lung disease remains a confusing topic owing to ever-changing histopathologic understanding of the various entities and frequent updates to antiquated clinical and pathologic classification schemes. Past classifications have been based on thoracic anatomic structures, dividing lesions into congenital malformations of the trachea, bronchi, lung, and pulmonary vasculature. Such divisions are controversial because the embryologic basis of these malformations is not clearly understood, as more recent…

Decreased Lung Density

Diseases that cause a decrease in lung density result in increased radiolucency (hyperlucency) on chest radiography and decreased attenuation on computed tomography (CT). Decreased lung density may result from obstructive overinflation without lung destruction (e.g., asthma, constrictive bronchiolitis), overinflation with lung destruction (e.g., emphysema), or a reduction in the quantity of blood and tissue in the absence of pulmonary overinflation (e.g., Swyer-James-McLeod syndrome, pulmonary thromboembolism). It…

Interstitial Patterns

Many diseases involve predominantly or exclusively the pulmonary interstitium. The differential diagnosis of the various entities on the chest radiograph and computed tomography (CT) is based on the pattern and distribution of abnormalities and on the presence of associated findings, such as lymph node enlargement or pleural effusion. Interstitial lung disease results in six distinct radiologic patterns of abnormality: septal, reticular, cystic, nodular, and ground-glass opacities…

Nodules and Masses *

Solitary Lung Nodule or Mass A pulmonary nodule is defined as any pulmonary lesion that is well-defined, discrete, approximately circular, and 3 cm or less in diameter. The term mass is used for lesions greater than 3 cm in diameter. The differential diagnosis of a nodule or mass detected on a radiograph or CT is very broad ( Table 4.1 ). However, more than 95% fall into one…

Atelectasis

Atelectasis is defined as less than normal inflation of all or part of the lung with a corresponding diminution in lung volume. Although the term collapse is often used synonymously with atelectasis, it should be reserved for complete atelectasis. Mechanisms of Atelectasis Mechanisms of atelectasis can be classified into five types: obstructive (resorptive), passive, compressive, adhesive, and cicatrization (scar). Obstructive Atelectasis Obstructive or resorptive atelectasis occurs…

Consolidation

Airspace consolidation is defined as replacement of gas within the airspaces by fluid, protein, cells, or other material. Consolidation is characterized on radiographs and computed tomography (CT) by the presence of one or more fairly homogeneous opacities associated with obscuration of the pulmonary vessels and little or no loss of volume. Homogeneous opacities that do not obscure the underlying pulmonary vessels are referred to as ground-glass…

Normal Chest Radiography and Computed Tomography

Radiography Technique Projections The standard radiographic views for evaluation of the chest are the posteroanterior (PA) and lateral projections with the patient standing; such projections provide the essential requirement for proper three-dimensional (3D) assessment ( Fig. 1.1 ). In patients who are unable to stand, anteroposterior (AP) upright or supine projections offer alternative but considerably less satisfactory views. The AP projection is of inferior quality because…

The Wrist

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The Elbow

Elbow Checklists 1 Radiographic examination AP External oblique Lateral 2 Elbow joint effusions and the fat pad sign Visible posterior fat pad Elevation of the anterior fat pad, the sail sign 3 Common sites of injury in adults Radial head and neck Olecranon Coronoid process of ulna Distal humerus 4 Common sites of injury in children and adolescents Supracondylar of the distal humerus Salter-Harris type 4…

The Shoulder

Shoulder Checklists 1 Radiographic examination AP external rotation AP internal rotation Axillary view Y-view Grashey (posterior oblique) view 2 Common sites of injury in adults Fractures Midshaft of clavicle Avulsion of the greater tuberosity of the humerus Surgical neck of the humerus Dislocations Acromioclavicular joint dislocation Dislocation of the glenohumeral joint Anterior dislocation Posterior dislocation Luxatio erecti 3 Common sites of injury in children and adolescents…

Peripheral Nerve Imaging: The Carpal Tunnel

The most common peripheral nerve compression syndrome is compression neuropathy of the median nerve at the carpal tunnel. The median nerve innervates the wrist and sends cutaneous sensory branches to innervate the palm, the palmar aspect of the first three digits, and the radial half of the fourth digit. The median nerve also innervates the superficial flexors of the first three rays, as well as the…

Imaging of the Sacral Plexus

The sacral plexus and sciatic nerve are formed within the pelvis from contributions of the ventral nerve roots of L4 through S4. The sciatic nerve originates from the sacral plexus within the pelvis and then exits the pelvis through the greater sciatic foramen. Technical advances in the surface coils and pulse sequences used for MRI now make it possible to display the normal anatomy and pathology…