Etiology: WP is, by far, the most common of the pulmonary vasculitides seen in children and typically presents with a triad of necrotizing granulomatous lesions in both the upper and lower respiratory tract, as well as glomerulonephritis. MPA is a nongranulomatous necrotizing vasculitis almost always seen with glomerulonephritis. CSS (also known as allergic granulomatosis and angiitis) typically presents with asthma and blood eosinophilia but is rare in children.¹ Most of the pulmonary vasculitides are immunologically mediated. WP, MPA, and CSS are associated with antineutrophil cytoplasmic antibodies (ANCA) and are sometimes referred to as ANCA-associated systemic vasculitides.

Most of the CVDs also have an autoimmune mechanism, SLE being the classic autoimmune condition associated with antinuclear antibody. These disorders are associated with a variable degree of inflammation of multiple organ systems, including the lung. Depending on the specific disorder, patients may present with arthritis, serositis, vasculitis, other soft tissue inflammation, or all of these.

Imaging: The common imaging findings of pulmonary vasculitis and CVDs are summarized in Table 57-1. The frequent imaging findings of WP are variable sized nodules, followed by ground-glass opacities and air space consolidation; 17% of the nodules show cavitation.⁸ The nodules are frequently surrounded by a halo of ground-glass opacity, which represents hemorrhage (e-Fig. 57-2 and Fig. 57-3). Airway wall thickening may also be seen, but airway strictures are significantly less common in children (3%) compared with adults (up to 59%).⁸ Diffuse alveolar hemorrhage (occurring in 44% of pediatric WP) is characterized by lobular or lobar regions of ground-glass opacity or airspace consolidation on CT.^9–11 It may also show the “crazy paving” pattern on CT, especially as it evolves.¹²

In the case of CVDs, pleural and pericardial effusions are the most common findings in the chest. Pulmonary findings are significantly less common but follow a similar pattern for most of these disorders and include ground-glass opacity and interstitial septal thickening, which may progress to pulmonary fibrosis. Despite normal chest radiographs or only minimal radiographic abnormalities in children with systemic sclerosis, HRCT demonstrates ground-glass opacities, peripheral areas of pulmonary fibrosis, and subpleural micronodules (Fig. 57-4).⁴ Some authors have reported occurrence of lipoid pneumonia in children with juvenile idiopathic arthritis, not associated with mineral oil ingestion.¹² “Shrinking lung syndrome” has been described in SLE and represents decrease in lung volume that manifests radiographically by an elevated diaphragm.^7,12,13

Treatment and Follow-up: Treatment for vasculitides and CVDs is primarily aimed at suppressing the immune response, typically with corticosteroids and chemotherapeutic agents. In patients with vasculitis, CVDs, or both, who experience diffuse alveolar hemorrhage, evolving changes may be seen on CT at follow-up. A more linear and interstitial type of pattern may develop with interlobular septal thickening and the appearance of the “crazy paving” pattern. If episodes of hemorrhage recur, this may also progress to interstitial fibrosis.⁹ Pulmonary involvement with CVD may progress to interstitial pulmonary fibrosis regardless of treatment, with advanced stages showing honeycombing. Pulmonary artery hypertension may also develop with advanced lung disease, especially in systemic sclerosis.

Follow-up imaging is primarily determined by clinical needs, symptoms, or both but is best performed with HRCT, as radiographic findings may be too subtle to identify changes. Progression of abnormal PFTs in patients with juvenile systemic sclerosis over time (forced expiratory volume in 1 second and forced vital capacity) correlate with worsening of changes on HRCT, suggesting that PFTs could potentially be used as a marker to determine when follow-up imaging may be needed.

Etiology: The etiology of ACS is complex and not always known. In a large multicenter study of 671 episodes, causes were found to be microvascular occlusion and infarction (16%), infection (29%), fat emboli from bone marrow infarcts (9%), and unknown in 46%. Chlamydia, Mycoplasma, and viral agents were the most common pathogens in cases caused by infection. One third of patients presented with symptoms of long bone pain caused by vasoocclusive crisis and developed ACS 2 to 3 days later.¹⁷

Imaging: Radiographic findings of ACS are nonspecific but, by definition, include the presence of a pulmonary opacity (e-Fig. 57-5). Opacities were noted in the lower lobes in about 90%, and pleural effusion was noted in 55% of cases in a large multicenter study (see Table 57-1).¹⁷

Although CT is not generally used in the setting of ACS, chronic sickle cell lung disease has been studied by using HRCT. Abnormal findings most pronounced at the lung bases include parenchymal bands, interlobular septal thickening, architectural distortion, and traction bronchiectasis. Honeycombing is unusual, in contrast to other types of pulmonary fibrosis.¹⁸

Treatment and Follow-up: Therapy for ACS includes hydration, analgesia, respiratory support (including bronchodilators), broad-spectrum antibiotics, transfusion therapy, and sometimes corticosteroids.¹⁹ Imaging follow-up is primarily dictated by clinical progression, improvement, or both and may be accomplished by using radiography.

Etiology: The etiology of LCH is not known. Most investigators believe it to be an immune-mediated condition, in which the Langerhans cells accumulate and cause an inflammatory reaction. In the lungs, destructive granulomatous lesions occur in the interstitial tissues, bronchial and bronchiolar epithelium, and subpleural septa that may eventually lead to cystic lesions.20,21 Pulmonary fibrosis occurs later in 10% of children and may demonstrate multiple small cysts giving the lung a honeycomb appearance.²³

Imaging: Radiologic findings of LCH vary widely with the extent of the disease and are summarized in Table 57-1. Initial chest radiography may be normal. Small nodules and cysts may be seen, with upper lobe involvement equal to or more extensive than lower lobe involvement (Fig. 57-6). The reticular appearance noted on chest radiography is often from multiple small cysts.^20,24 LCH is the most common cause of acquired extensive cystic lung disease in children (e-Fig. 57-7). Spontaneous pneumothorax occurs in about 11% of patients with pulmonary involvement and may be the first indicator of pulmonary disease.²⁵ However, it may be also a manifestation of more advanced disease, as in adolescents who more often have large coalescent cysts (see e-Fig. 57-7).¹²

CT is indicated for neonates with LCH and any patient with abnormalities on chest radiography.²¹ HRCT findings in LCH are characterized by small nodules (with or without cavitation) with upper and middle lobe predominance (e-Fig. 57-8).^12,20,26 The pleura may be thickened and sometimes replaced by a thick layer of granulomatous tissue. However, pleural effusions are rare.²⁷ Mediastinal and hilar adenopathy is also rare in children with pulmonary LCH.^20,24

Treatment and Follow-up: Treatment of pulmonary LCH depends on the extent of disease and whether “risk” organs are involved. Generally, the first line of treatment is corticosteroids, vinblastine, or both, with duration of therapy being determined by response. Radiation therapy has fallen out of favor except for treating unstable bone lesions.²¹ Imaging follow-up for pulmonary LCH depends on clinical symptoms and is best performed with CT.

Etiology: Gaucher disease is caused by a deficiency of the enzyme glucocerebrosidase that results in an accumulation of glucocerebroside in phagocytic cells. Pulmonary involvement is most common in patients with neuronopathic types. Neimann-Pick disease is caused by a deficiency of sphingomyelinase, resulting in accumulation of sphingomyelin. Progressive pulmonary fibrosis has rarely been reported in Neimann-Pick disease.²⁸

Imaging: A diffuse reticular lung pattern may be seen on chest radiography with Gaucher disease.²⁹ Niemann-Pick disease may produce similar findings.²⁷ Lipoid pneumonia has been described in patients with Neimann-Pick disease.³⁰ Imaging findings are summarized in Table 57-1.

Treatment and Follow-up: Visceral involvement may improve with enzyme replacement therapy in Gaucher disease, and this therapy may offer an alternative to lung transplantation. The current treatment for Neimann-Pick disease is whole lung lavage.28,30 CT is more sensitive than plain radiography for imaging follow-up, when clinically warranted.

Etiology: Cardiogenic pulmonary edema occurs significantly less frequently in children than in adults. The common underlying causes for cardiogenic pulmonary edema include left-to-right shunting lesions, left ventricular outlet obstruction, obstruction of pulmonary venous return, or cardiomyopathy (e-Fig. 57-11).³¹ Cardiogenic pulmonary edema progresses in severity as pulmonary capillary wedge pressure increases.

Imaging: On chest radiography, cardiomegaly is usually found except in instances of pulmonary venous obstruction, in which interstitial edema is present in the absence of cardiac enlargement (see Fig. 57-9).

Early findings in interstitial edema in children with cardiogenic pulmonary edema are indistinct vascular margins and bronchial wall thickening. Interlobular septal thickening (septal lines or Kerley B lines) and interlobar fissural thickening are also often seen. In infants and young children, fissural thickening is often more easily recognized than Kerley lines and is therefore an important clue for diagnosing cardiogenic pulmonary edema in children (see Fig. 57-9). An indirect radiographic finding often seen in children with CHD is hyperinflation. This may be a pitfall for the imager if he or she attributes the findings of peribronchial thickening and hyperinflation to airways disease and does not recognize them as subtle findings of interstitial edema (see Fig. 57-9). Alveolar edema usually occurs after development of interstitial edema and is the most recognizable radiographic finding of pulmonary edema (see Fig. 57-10 and e-Fig. 57-11). The classic appearance of acute alveolar edema is a central or “butterfly” distribution of airspace disease, with central edema and sparing of the lung periphery. Pleural effusions are also usually present (see e-Fig. 57-11).

Although not commonly used to diagnose pulmonary edema, CT is sensitive for the detection of pulmonary edema of any etiology. CT shows peribronchial cuffing, septal lines, ground-glass opacities, and air space consolidation in order of increasing severity (e-Fig. 57-12).^33,34

Occasionally, pulmonary edema is asymmetric or unilateral. This may be related to patient position (given the dependent nature of the edema) or to the presence of asymmetric pulmonary arterial supply or pulmonary venous drainage, particularly in patients with CHD.

Treatment and Follow-up: Treatment for cardiogenic pulmonary edema is generally supportive and includes corrective or palliative treatment for CHD. Diuretics and inotropes may be used for cardiac dysfunction. Ventilator support is provided, if needed. Extracorporeal membrane oxygenation and other types of ventricular assist devices are now being used more frequently in the setting of pediatric cardiac failure.³⁵ Typically, imaging follow-up with chest radiography is adequate, although CT may be used to clarify the vascular anatomy.

Etiology: Many episodes of noncardiogenic pulmonary edema progress to ARDS. ARDS accounts for 1% to 3% of pediatric intensive care admissions, and the mortality in various series ranges from 40% to 60%.³² Sepsis, near-drowning, pneumonia, and smoke inhalation are the most frequent antecedents to pediatric ARDS. In most cases, ARDS progresses through stages of immediate lung injury, exudative alveolitis, fibroproliferative repair, and, in survivors, recovery. Ventilation–perfusion imbalance leads to varying degrees of hypoxemia.³²

Neurogenic pulmonary edema may occur with increased intracranial pressure, which, in theory, causes a shift of blood from the systemic to the low-resistance pulmonary circulation. Pulmonary edema caused by renal disease (chronic renal failure, glomerulonephritis, nephrotic syndrome, or all of these) is felt to be multifactorial in mechanism, including factors such as fluid retention and hypoproteinemia (see e-Fig. 57-12). Although uncommon, postobstructive pulmonary edema may also occur in upper airway obstruction from conditions such as croup, epiglottitis, foreign body obstruction, and near-strangulation or when relief of upper airway obstruction occurs. The mechanism is thought to be an abrupt decrease in intrathoracic pressure caused by an attempt to inhale against a closed upper airway, also called negative-pressure pulmonary edema.³¹

Pulmonary edema may also develop after inhalation of a variety of noxious fumes or soluble aerosols. Aspiration of hypertonic water-soluble contrast agents may also produce pulmonary edema.

Imaging: The radiographic pattern for ARDS is a multiple stage continuum (Fig. 57-13).^36,37 First, the radiograph is reflective of the initial insult, or it may be clear, or both. In 12 to 24 hours, bilateral pulmonary opacities develop, consistent with noncardiogenic pulmonary edema, and opacities become progressively more confluent.³⁷ Subsequent improvement or continued worsening may be seen in the next several days. For patients with progression, the course often is then complicated by air leak phenomenon (pneumothorax, pneumomediastinum, pulmonary interstitial emphysema), with or without ventilator-associated infections. Additionally, further progression to chronic changes of fibrosis may occur.^32,36,37

The pulmonary findings of noncardiogenic pulmonary edema (e.g., ARDS) are similar to that of cardiogenic pulmonary edema, but the radiographs typically do not show cardiomegaly (see e-Fig. 57-12, Fig. 57-14, and e-Fig. 57-15).³⁷ Pleural effusions may not be a dominant finding, but they are frequently seen, particularly in patients requiring maximum clinical support as a manifestation of anasarca.

Glomerulonephritis and nephrotic syndrome are often sufficiently characteristic, aiding the radiologist to suggest the correct diagnosis. A child or teenager presents without a known cardiac history with a basilar predominant interstitial edema pattern, often with pleural effusions (see e-Fig. 57-12). Glomerulonephritis may be distinguished from nephrotic syndrome by its tendency to show mild cardiomegaly and increased pulmonary vascularity.³⁸

Treatment and Follow-up: Treatment of noncardiogenic pulmonary edema is directed toward the primary cause, is generally supportive, or both. Ventilatory support is often needed. The use of positive end-expiratory pressure with mechanical ventilation has been shown by CT to improve ventilation of dependent regions of the lung in a setting of ARDS.37,39 Extracorporeal membrane oxygenation is increasingly being used for children with severe respiratory failure. Pulmonary edema from neurogenic causes or upper airway obstruction usually resolves fairly rapidly, often within 12 to 48 hours (see Fig. 57-14).³¹ Typically, imaging follow-up will be performed with chest radiography, as needed.

Survivors of ARDS may have long-term sequelae, often demonstrable by pulmonary function testing. Follow-up chest radiography most often show a return to normal (80%) but may demonstrate increased interstitial markings, hyperaeration, or both (see Fig. 57-13, E and F).^32,37,40

Etiology: Deep venous thrombosis (DVT) is a common precursor to PE in children. In one study, 56% of PEs in children were found to be associated with thrombosis at another location.⁴⁶ However, even occurrence of a DVT in a child will usually have a predisposing cause such as the presence of a central venous catheter. Whereas lower extremity DVT is most common in adults, upper extremity DVT is more common in children (accounting for two thirds of DVTs) because of the association with central venous lines.^44,46,50 Other factors predisposing to thromboembolism include malignancy, hypercoagulable states (such as SCD, SLE, or coagulation disorders), CHD, trauma, infection, recent surgery, nephrotic syndrome, and use of birth control pills (see Fig. 57-16 and e-Fig. 57-17).⁴⁶ A recent study found a nearly 2% prevalence of unsuspected PE in pediatric oncology patients undergoing routine thoracic CT studies.⁵¹

Imaging: Radiographic findings of PE are unfortunately nonspecific. If the embolic episode occurs without infarction, the result of chest radiography is most often normal. If it is abnormal, it may show localized or generalized oligemia (Westermark sign), an enlarged pulmonary artery, or loss of lung volume. PE with associated infarct classically appears as a truncated cone of homogeneous opacity located at the lung periphery and abutting the pleural surface (Hampton hump), but in fact, this pattern is uncommon.

CTPA has a variable but high sensitivity (60% to 100%) and high specificity (81% to 100%) for the diagnosis of PE and provides direct visualization of emboli in central and in smaller, peripheral pulmonary arteries (Fig. 57-16 and e-Fig. 57-17).⁴⁴ Successful technique requires a multidetector helical scanner and the use of a well-timed contrast bolus, which allows detection of the pulmonary artery filling defects. The interpretation is more challenging if the contrast enhancement is suboptimal or if patient movement limits the image quality. Adjacent hilar lymph nodes may be a pitfall but reformatted images in multiple planes usually clarify their extrinsic location. In addition to the direct vascular findings, CT may also reveal a region of oligemia, peripheral pulmonary consolidation (infarct) with absent or poor enhancement, or both (see Fig. 57-16 and e-Fig. 57-17). Wedge-shaped peripheral consolidation was found to be significantly associated with presence of PE on a review of CTPA studies in children.⁵²

Nuclear medicine assessment of pulmonary ventilation and perfusion (V/Q scan) remains an available imaging modality for evaluation of PE in children. A single segmental or larger perfusion defect, with mismatched normal ventilation, signals a high probability of PE. Although some are advocating continued use of V/Q scans in select populations with normal chest radiography results, CTPA is currently preferred in most centers, likely because of the many advantages of CT: it requires minimal patient cooperation, it is rapidly available, and it screens for alternate diagnoses.45,46,53–56

Many studies are underway to determine the utility of contrast-enhanced magnetic resonance angiography (CEMRA) for the diagnosis of PE. This technique would be particularly advantageous in children given the lack of radiation exposure and potential to screen upper extremity veins for thrombosis at the same time as the evaluation for PE.⁴⁴ PIOPED III (Prospective Investigation of Pulmonary Embolism Diagnosis III) results showed sensitivity of 78% and specificity of 99% in technically adequate CEMRA studies, but unfortunately 25% of studies were not considered technically adequate. Sensitivity was better for the central pulmonary arteries and decreased progressively in the more distal branches.⁵⁶ The advent and use of new blood pool magnetic resonance imaging contrast agents may improve the capabilities of CEMRA.

Conventional pulmonary angiography is still considered the gold standard for diagnosis of PE, but it is rarely necessary and is infrequently used.

Treatment and Follow-up: Anticoagulation therapy is generally used to prevent extension of thrombus and the development of late complications such as recurrences and postthrombotic syndrome. Most children are treated primarily on the basis of recommendations for adults, since large clinical trials of antithrombotic therapy in children are lacking.44,46 Traditionally, the first-line anticoagulant used was unfractionated heparin, but bleeding complications are 2% to 18%, depending on patient population, and it requires intravenous access for administration. The low-molecular-weight heparins being used more frequently have several advantages: lower bleeding complications (0% to 5%), subcutaneous administration, and reduced need for monitoring. These advantages make it ideal for outpatient treatment.^44,46

Thrombolytic therapy causes faster resolution of the embolus, but data regarding efficacy and safety in children are lacking. The agent most commonly used is tissue plasminogen activator. A substantially higher risk of bleeding complications exists, with one study reporting bleeding in 68% of patients and transfusion required in 39% of treated children. Given that risk, most feel that thrombolytic therapy should only be considered in pediatric patients with unstable hemodynamic condition, massive PE, or both.44,46

Imaging follow-up for PE is based on clinical factors and is best performed with CTPA.

Etiology: In septic emboli, hematogenous spread of infection from the original site occurs, as well as deposition of bacteria in end organs. Osteomyelitis is a common primary site of septic embolic disease (Fig. 57-18 and e-Fig. 57-19). In one study from Taiwan, 8 out of 10 pediatric patients with septic emboli had methicillin-resistant Staphylococcus aureus as the responsible organism, and most patients had primary skin, soft tissue, or bone infections.⁴⁸ Lemierre syndrome is septic thrombophlebitis of the internal jugular vein secondary to bacterial pharyngitis or tonsillitis, usually from Fusobacterium necrophorum, with subsequent septicemia and systemic spread of infection and lung involvement in 97% of cases (Fig. 57-20).^47,57,58

Imaging: The classic radiologic finding is one or more cavitary peripheral nodules, although radiographs more often show nonspecific airspace consolidation (see e-Fig. 57-19). CT is the most sensitive imaging test, more frequently demonstrating cavitation of the nodules (in 85% to 100%) and presence of a “feeding vessel” (in 50% to 71%). Hilar lymph node enlargement and pleural effusions may also be seen.^47,48

Treatment and Follow-up: Antibiotics is the mainstay for treating the primary source of infection. If the source is unknown, echocardiography is indicated to look for endocarditis. Drainage of focal abscesses is indicated. Currently, no consensus exists on the use of anticoagulation in the setting of Lemierre syndrome.⁴⁷ Imaging follow-up may be performed with radiography or CT. Generally, if clinical improvement is prompt, radiography will be adequate. If fever or other symptoms persist, CT may be needed to better assess for persistent sources of infection.

Etiology: Fat droplets, typically from the marrow cavity, appear in blood and lodge in the capillaries of the lungs, brain, and other organs. Dyspnea, cyanosis, and tachycardia with cough and fever are the common clinical symptoms, and fat globules may usually be found in blood and urine on laboratory evaluation.

Imaging: Most often, the result of chest radiography is normal. Abnormalities, when present, are usually nonspecific and include airspace consolidation from alveolar hemorrhage and edema, more commonly peripheral and basilar in location. The time lapse between trauma and the development of radiographic findings is usually 1 to 2 days. Such delay may be helpful in differentiating fat embolism from traumatic lung contusion; in the latter, the chest radiograph is abnormal initially.⁵⁹

Treatment and Follow-up: Treatment of pulmonary fat embolism is generally supportive. Radiographic changes resulting from fat embolism usually disappear gradually within a week to 10 days.

Etiology: Chemotherapeutic agents (such as cyclophosphamide, bleomycin, busulfan, cisplatin, nitrosureas, mitomycin-C, and methotrexate) are the most common drugs associated with pulmonary toxicity (occurring in up to 10% of patients).61,62 These medications may cause interstitial pneumonitis or fibrosis, hypersensitivity reaction, ARDS, or bronchiolitis obliterans with organizing pneumonia. Amiodarone may cause interstitial thickening, bronchiolitis obliterans with organizing pneumonia, or both.⁶¹

Airway hyperreactivity has been associated with ingestion of aspirin and nonsteroidal antiinflammatory agents. Hypersensitivity reactions may be produced by reactions to methotrexate, sulfonamides, and nitrofurantoin.⁶¹ Noncardiogenic pulmonary edema may result from overdoses of heroin, morphine, methadone, and cocaine.^61,63 Pulmonary hemorrhage may be seen after administration of anticoagulants, surfactants, and penicillamine.⁵²

Imaging: Radiographic findings of drug-induced reactions are generally nonspecific, consisting of heterogeneous pulmonary opacities, homogeneous pulmonary opacities, or both.⁶⁰

HRCT is most useful for early diagnosis of pulmonary toxicities. The findings depend on the histologic process and may include interstitial disease, alveolar disease, or both.60,61 Interstitial pneumonitis and fibrosis, typical of bleomycin, produce ground-glass opacities, areas of consolidation, and irregular linear opacities that tend to predominate in the lower lung zones. Methotrexate hypersensitivity resembles hypersensitivity pneumonia, showing ground-glass opacities and poorly defined centrilobular nodules. ARDS results in predominantly dependent airspace consolidation. The least common reaction, a bronchiolitis obliterans with organizing pneumonia-like reaction, causes peribronchial or subpleural areas of consolidation.⁶¹

Airway reactivity is associated with air trapping on imaging. The appearance of noncardiogenic pulmonary edema and pulmonary hemorrhage has been previously discussed earlier in this chapter.

Treatment and Follow-up: Removal of the causative agent is the ideal management for drug-induced pulmonary disease if the toxicity can be recognized and the removal is feasible. Unfortunately, some pulmonary toxicities are often irreversible. If symptoms persist, radiography and CT may help in follow-up management.

Etiology: Important factors in determining whether the lungs are damaged include the volume of tissue irradiated, the dosage and its fractionation, the relative biologic effectiveness of the therapy employed, and the use of concomitant chemotherapy. Radiation-induced lung injury is typically categorized as early pneumonitis (1-6 months) and late pulmonary fibrosis (>6 months).⁶⁶

Imaging: Radiographic changes, if present, usually appear a few months after the cessation of radiation therapy. The radiographic appearance initially is that of an ill-defined alveolar process. CT typically shows ground-glass opacity in a sharply defined zone not conforming to anatomic boundaries. As the process evolves, it becomes more interstitial in appearance until changes recognized as radiation fibrosis appear (e-Fig. 57-21). CT is more sensitive than chest radiography in showing these findings. If the mediastinum has been irradiated, a central perimediastinal, sharply delineated area of linear increased opacity corresponding to the radiation portal is typically seen (see e-Fig. 57-21).^64,66

Treatment and Follow-up: Corticosteroids are sometimes used for managing acute radiation-induced pneumonitis, and long-term treatment is aimed at control of symptoms.⁶⁶ Choice of follow-up imaging is largely determined by clinical factors. CT will be more sensitive to identify subtle findings of fibrosis.

Etiology: Inhalation injuries are rare in pediatric fire victims but should be suspected in those with burns in the head-and-neck area, blackened sputum, and respiratory symptoms. Thermal injury is most likely to produce upper airway edema. More peripheral airway and airspace injuries are usually secondary to toxic chemical effects of the products of combustion. Typically, pulmonary burns progress through three distinct clinical stages: (1) bronchospasm (1 to 12 hours after the burn), (2) pulmonary edema (6 to 72 hours), and (3) bronchopneumonia (after 60 hours) (Fig. 57-22). Bacterial pneumonia is very frequent after the third or fourth day of injury and should be anticipated.³²

Inhalation injury from chlorine gas inhalation has been reported in children. This irritant gas is found in swimming pool disinfectants and household cleaning agents. It reacts with the water in tissue to produce hydrochloric acid, which leads to mucosal necrosis. Irritation of the upper respiratory tract, cough, and wheezing are early findings.32,67

Another inhalation injury that may occur in infants is caused by inhalation of the small (approximately 5 micrometers) particles of hydrous magnesium silicate present in talcum powder. Inhaled talc produces airway obstruction and impairs ciliary action, which leads to inflammation. Symptoms of cough and respiratory distress are rapid after exposure.⁶⁸

Passive smoking is associated with an increased rate of respiratory illness in infancy and childhood. The frequency of reactive airways disease is increased in exposed infants.69,70

Imaging: The results of early radiographs are often normal in smoke inhalation, but diffuse or focal patchy opacities or pulmonary edema may be noted (see Fig. 57-22). More diffuse opacities, which usually appear after a latent period of 12 to 48 hours, may clear slowly. Rapid appearance of total or subtotal lung consolidation has been described in up to 10% of burned children and is associated with high early mortality. ARDS is a serious and common complication of inhalation injuries and burns.³²

With chlorine gas inhalation, the onset of pulmonary edema is often rapid. The results of chest radiography may be normal or may show hyperinflation or pulmonary edema.67,68 With talcum powder inhalation, chest radiography may show hyperinflation and patchy opacities.⁶⁸

Treatment and Follow-up: Treatment, as for noncardiogenic pulmonary edema, is primarily supportive. Late sequelae, including severe bronchiectasis, asthma, and bronchiolitis obliterans, may be noted after smoke inhalation.³² Follow-up radiography is adequate if the patient shows clinical improvement. CT may be needed if clinical symptoms persist in a delayed setting.

Etiology: Aspirated or inhaled material usually results in an intense chemical pneumonitis causing damage to the respiratory epithelium and development of cyanosis through displacement of alveolar gas by the hydrocarbon.³²

Imaging: Although changes may be evident on chest radiography as early as 30 minutes after aspiration, the findings may be delayed several hours; virtually all affected children with lung disease have abnormal chest radiographs by 12 hours (see Fig. 57-13 and e-Fig. 57-23).³² The typical pattern of hydrocarbon pneumonitis is one of patchy airspace consolidation and alveolar edema involving predominantly the medial basilar portions of the lungs bilaterally. Pneumatoceles are a well-known complication of hydrocarbon aspiration but only develop in 10% of children.⁷¹

Treatment and Follow-up: Treatment is supportive. Resolution of the radiographic changes usually lags behind clinical improvement and may take weeks or months. CT may be performed if improvement does not progress as expected.

Etiology: Lipids aspirated during oral administration of mineral oil may result in an insidious chronic process that produces an intense lung response and may result in severe lung injury. Histologic proof of exposure is gained by finding lipid-laden macrophages and lipid material in alveoli on biopsy. However, the current diagnostic method of choice for diagnosing lipoid pneumonia is by analysis of bronchoalveolar lavage fluid.⁷²

Imaging: The typical radiographic pattern of lipoid pneumonia is perihilar and basilar airspace opacities (Fig. 57-24 and e-Fig. 57-25). CT shows areas of ground-glass opacity or more confluent airspace disease (see Fig. 57-24 and e-Fig. 57-25). On CT, the presence of fat attenuation values of the airspace disease (occurring in 71% of children) should alert the radiologist to the diagnosis of lipoid pneumonia.⁷³ In adults and children with lipoid pneumonia, the crazy-paving pattern has also been noted on thin-section CT.^72–74

Treatment and Follow-up: Cessation of exposure and clearing of the oil by multiple bronchoalveolar lavages is usually followed by slow clearing of lung opacities and clinical improvement.⁷² CT and chest radiography are usually used for follow-up.

Etiology: Submersion time, volume of water aspirated, severity of acidosis, and length of delay in cardiopulmonary resuscitation all correlate directly with morbidity and mortality. Most submersion victims aspirate a small amount of water that may contain vomitus or a variety of contaminants. Laryngospasm occurs, which may prevent further aspiration. In about 15% of patients, laryngospasm persists and death is by anoxia (i.e., “dry drowning”).³²

Imaging: The radiologic pattern of near-drowning is of pulmonary edema, and the severity depends predominantly on the amount of water aspirated. Opacities are usually bilateral and symmetric, and a significant delay, sometimes as long as 24 to 48 hours after near-drowning, may occur in the appearance of edema (Fig. 57-26).³²

Treatment and Follow-up: Treatment is primarily supportive with ventilatory support, if needed, in cases of severe respiratory distress. Radiography is usually adequate for imaging follow-up.

Etiology: The etiology of PAM is currently unknown. However, the tiny stones in the alveoli consist of concentric calcium rings, which measure from 0.01 to 3 mm in size, are similar to bone histologically, radiographically, and metabolically. The number and size of the calculi and the amount of interstitial reaction increase with the age of the patient and the duration of the disease.75,76

Imaging: On chest radiography, in children with PAM, diffuse ground-glass opacities were more common than nodular calcific densities. HRCT shows ground-glass opacities and calcific densities in the lung, pleura, and interlobar septae.⁷⁷ The calcified lung lesions demonstrate an avidity for bone scintigraphy agents.⁷⁶

Treatment and Follow-up: Virtually all types of treatment for PAM have been ineffective except lung transplantation.⁷⁶ CT or chest radiography may be used for follow-up, but CT shows the distribution and size of the calcifications more reliably.

Etiology: Focal pulmonary calcifications in childhood are usually the result of granulomatous infection, most commonly tuberculosis or histoplasmosis. Diffuse calcifications are probably dystrophic (calcification caused by tissue damage) and are most commonly seen after varicella infection. Metastatic calcification (calcification in normal tissue) is caused by abnormal calcium and phosphorous metabolism, usually in one of the following clinical situations: chronic renal failure and secondary hyperparathyroidism, acute renal failure, after renal transplantation, and after cardiac surgery.⁷⁸

Imaging: Initially, plain radiography shows airspace consolidation or nonspecific nodular opacities, which may demonstrate a progressive increase in opacity. These opacities may be mistaken for an infectious process such as pneumonia. CT is more sensitive than chest radiography for the definitive diagnosis of pulmonary calcification.

Treatment and Follow-up: Besides treatment for a discovered active granulomatous process, no treatment or follow up is needed for the majority of pulmonary calcifications.