(Radiographics. 2000;20:673-685.)
© RSNA, 2000
Aspiration Diseases: Findings, Pitfalls, and Differential Diagnosis1
Tomás Franquet, MD,
Ana Giménez, MD,
Nuria Rosón, MD,
Sofía Torrubia, MD,
José M. Sabaté, MD and
Carmen Pérez, MD
1 From the Department of Radiology, Hospital de Sant Pau, Universidad Autónoma de Barcelona, Avda San Antonio Maria Claret 168, Barcelona 08125, Spain. Presented as a scientific exhibit at the 1998 RSNA scientific assembly. Received April 1, 1999; revision requested May 7 and final revision received December 20; accepted December 22. Address reprint requests to T.F. (e-mail: 19429tfc@comb.es).
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Abstract
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The aspiration of different substances into the airways and lungs may cause a variety of pulmonary complications. These disease entities most commonly involve the posterior segment of the upper lobes and the superior segment of the lower lobes. Esophagography and computed tomography (CT) are especially useful in the evaluation of aspiration disease related to tracheoesophageal or tracheopulmonary fistula. Foreign body aspiration typically occurs in children and manifests as obstructive lobar or segmental overinflation or atelectasis. An extensive, patchy bronchopneumonic pattern may be observed in patients following massive aspiration of gastric acid or water. CT is the modality of choice in establishing the diagnosis of exogenous lipoid pneumonia, which can result from aspiration of hydrocarbons or of mineral oil or a related substance. Aspiration of infectious material manifests as necrotizing consolidation and abscess formation. The relatively low diagnostic accuracy of chest radiography in aspiration diseases can be improved with CT and by being familiar with the clinical settings in which specific complications are likely to occur. Recognition of the varied clinical and radiologic manifestations of these disease entities is imperative for prompt, accurate diagnosis, resulting in decreased morbidity and mortality rates.
Index Terms: Bronchiolitis, 671.2191, 671.458 • Foreign bodies, in air and food passages, 60.458, 60.46 • Lung, diseases, 60.21, 60.458 • Lung, infection, 60.21, 60.458
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Introduction
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The term aspiration describes a variety of situations involving the intake of solid or liquid materials into the airways and lungs (1). Alcoholism is probably the most important predisposing factor for pulmonary aspiration in adults, although other factors (eg, general anesthesia, loss of consciousness, structural abnormalities of the pharynx and esophagus, neuromuscular disorders, deglutition abnormalities) may also contribute to aspiration. The clinical and radiologic manifestations are protean, varying from asymptomatic focal inflammatory reaction with few or no radiologic abnormalities to severe life-threatening disease (1). The major complication associated with aspiration is pulmonary infection. Aspiration can lead to the development of lobar or segmental pneumonia, bronchopneumonia, lung abscess, and empyema. The posterior segment of the upper lobes and the superior segment of the lower lobes are the most commonly involved lung sites in aspiration disease, which may mimic other pulmonary diseases such as alveolar proteinosis (2) or neoplasms such as bronchogenic carcinoma (3) or bronchioloalveolar cell carcinoma (4). Computed tomography (CT) has proved useful in the evaluation of aspiration diseases that are not visible on conventional chest radiographs. However, certain lesions such as exogenous lipoid pneumonia can have unusual CT appearances that may lead to misinterpretation (5). Recognition of the varied clinical and radiologic manifestations of these disease entities is imperative for prompt, accurate diagnosis, resulting in decreased morbidity and mortality rates.
In this article, we discuss and illustrate the spectrum of radiologic manifestations, diagnostic pitfalls, and differential diagnoses associated with a variety of aspiration diseases. These include diseases associated with tracheoesophageal or tracheopulmonary fistula; diseases caused by aspiration of foreign bodies, liquids, or infectious material; and other aspiration diseases (lentil aspiration pneumonia, aspiration bronchiolitis, obliterative bronchiolitis).
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Tracheoesophageal and Tracheopulmonary Fistulas
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Congenital Tracheoesophageal Fistula
Failure of the tracheoesophagus to differentiate from the primitive foregut may manifest as any of a variety of congenital variations in tracheal development (6). The development of recurrent pneumonias in neonates is often the result of direct lung contamination from a congenital tracheoesophageal fistula (6). Acute episodes of aspiration are symptomatic, and patients usually present with symptoms of pneumonia or respiratory distress. The radiologic manifestations vary depending on the extent and severity of the disease. The most common radiographic finding is bronchopneumonia with patchy air-space areas of increased opacity (7). It is generally agreed that the most useful diagnostic imaging modality is esophagography and that barium is the best contrast agent to use in assessing for this lesion (Fig 1) (7).
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Figure 1. Tracheoesophageal fistula in a 3-day-old infant with respiratory difficulty after feeding. Barium esophagogram clearly depicts a fistula between the trachea and the midesophagus (arrowhead). Opaque contrast material is seen filling the bronchi of the right lower lobe.
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Acquired Tracheoesophageal or Tracheopulmonary Fistula
In adults, esophageal fistulas are usually acquired lesions. They may occur as a complication of intrathoracic malignancies (60% of cases), infection, or trauma (8). Fistulous connections between the esophagus and the lung, bronchi, or trachea are exceedingly rare in the absence of the usual predisposing factors (9); however, fistulas may occur in 5%–10% of patients with advanced esophageal cancer (8,10). In such cases, radiation therapy carries a high risk of fistula formation (11,12). Tracheoesophageal fistula is incurable, and once this complication has developed, the prognosis is extremely poor (10). Radiographic findings are nonspecific, and the diagnosis should be strongly suspected in patients with a known esophageal carcinoma in whom there is evidence of recurrent pneumonias. Pulmonary consolidations are usually unilateral but may involve both lungs. The clinical manifestations of tracheoesophageal fistula may be acute, subacute, or chronic. Diagnosis is usually made with contrast material–enhanced fluoroscopy (Fig 2). However, CT may be helpful in diagnosing a fistula in patients with normal findings at esophagography (13).
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Figure 2. Postradiation pulmonary-esophageal fistula in a 65-year-old man with advanced esophageal carcinoma. Contrast-enhanced fluoroscopic image from a barium study reveals a fistula between the esophagus and the lung parenchyma. Note the retrograde alveolar filling by contrast material.
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Foreign Bodies
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Aspirated foreign bodies are by far the most common cause of intraluminal airway abnormalities in childhood (1,14,15). The most commonly inhaled foreign bodies are food and broken fragments of teeth, which frequently lodge in a main or lobar bronchus (14,15). Most patients are children who present with varying degrees of cough and a recent history of foreign body aspiration. In most cases, radiographic manifestations include obstructive lobar or segmental overinflation or atelectasis (Figs 3, 4). Diagnosis requires careful integration of clinical data and radiographic findings, and a definitive diagnosis is usually made with conventional chest radiography. CT is far more sensitive than chest radiography in demonstrating radiolucent foreign bodies (16,17). In some instances, CT may provide additional diagnostic information by demonstrating subtle low-attenuation intrabronchial material, which is often the only finding that can help suggest the diagnosis (16,17). In most pediatric cases, aspiration of a foreign body is diagnosed immediately or within 2–3 days of the event; rarely, however, the diagnosis is not made for weeks or even months. Once a foreign body enters the lung parenchyma, prolonged irritation with intermittent infections may cause massive hemoptysis (14). At radiology, an aspirated foreign body may occasionally mimic a congenital malformation or neoplasm (Fig 5).
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Figure 3. Obstructive air trapping in a 6-year-old boy. Expiratory chest radiograph demonstrates a metallic foreign body in the right lower lobe bronchus (arrowheads). Air trapping is seen in the right lower lobe.
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Figure 4. Obstructive atelectasis in a 10-year-old boy who had aspirated vegetable matter. Posteroanterior chest radiograph shows complete collapse of the left lung. A posteroanterior chest radiograph obtained after bronchoscopic removal of the aspirated material (not shown) appeared normal.
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Figure 5. Foreign body aspiration in an asymptomatic 13-year-old boy. CT scan shows a pulmonary mass in the right lower lobe with surrounding ground-glass attenuation due to bloody intraalveolar material. The aspirate proved to be vegetable matter at surgery.
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Foreign body aspiration is unusual in adults and is often overlooked as a cause of airway obstruction (3). Although the condition is often clinically silent, life-threatening hemoptysis may develop (3,17). Diagnosis can be difficult because patients may forget previous episodes of aspira
tion. Radiologic manifestations are nonspecific and include chronic volume loss in the affected lobe, recurrent pneumonias, and bronchiectasis (14,15). Rarely, the development of a chronic inflammatory reaction around the inhaled material may lead to intrabronchial mass formation. In such cases, a foreign body can also manifest at conventional chest radiography or CT as a centrally located mass with lobar or segmental collapse that must be differentiated from bronchogenic carcinoma (Fig 6) (3).
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Figure 6. Pseudotumoral left hilar mass in a 52-year-old man with hemoptysis. CT scan shows a large, solid mass in the left hilar region associated with left lower lobe collapse. A bronchogenic carcinoma was suspected. Surgery revealed a pistachio nut surrounded by a significant chronic inflammatory reaction.
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Aspiration of Liquids
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Gastric Acid Aspiration (Mendelson Syndrome)
Vomiting with massive aspiration of gastric contents is a very frequent phenomenon and is probably one of the most common causes of aspiration diseases (18). Lesion characteristics depend to a large extent on the nature of the material aspirated. Gastric acid with a pH less than 2.5 can cause pathologic reactions varying from mild bronchiolitis to hemorrhagic pulmonary edema. The posterior segments of the upper lobes and the superior segments of the lower lobes are the most frequently involved lung sites when the patient is recumbent. Related gastrointestinal conditions include vomiting, gastroesophageal reflux, achalasia, and hiatal hernia (19). Acid liquid introduced into the airways is rapidly disseminated throughout the bronchial tree and lung parenchyma, producing a chemical pneumonitis within minutes. The magnitude of injury is directly related to the pH and volume of the aspirated material. The overall mortality rate associated with massive aspiration of gastric acid is approximately 30% and is greater than 50% in patients with initial shock or apnea, secondary pneumonia, or adult respiratory distress syndrome (20).
Classic radiographic findings in acute gastric acid aspiration include bilateral perihilar, ill-defined, alveolar consolidations; multifocal patchy infiltrates; and segmental or lobar consolidation, which is usually localized to one or both lung bases (Fig 7) (18–20).
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Figure 7a. Acute aspiration pneumonia (Mendelson syndrome) in a 68-year-old man who had undergone surgery for intestinal obstruction. (a) Anteroposterior chest radiograph obtained less than 2 hours after surgery demonstrates a focal consolidation in the right lower lobe, a finding that is consistent with aspiration pneumonia. (b) Anteroposterior chest radiograph obtained 24 hours later shows the development of extensive bilateral air-space consolidation, a finding that is typical of acute pulmonary edema.
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Figure 7b. Acute aspiration pneumonia (Mendelson syndrome) in a 68-year-old man who had undergone surgery for intestinal obstruction. (a) Anteroposterior chest radiograph obtained less than 2 hours after surgery demonstrates a focal consolidation in the right lower lobe, a finding that is consistent with aspiration pneumonia. (b) Anteroposterior chest radiograph obtained 24 hours later shows the development of extensive bilateral air-space consolidation, a finding that is typical of acute pulmonary edema.
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Near Drowning
The acute aspiration of massive amounts of water produces a pulmonary edema that is radiographically indistinguishable from pulmonary edema from other causes (18,19). The clinical significance of near drowning depends more on the volume of water aspirated than on whether the aspirate is fresh water or salt water (21,22).
Classic chest radiographic findings in severe near drowning consist of alveolar edema with extensive "fluffy" areas of increased opacity that tend to coalesce throughout both lungs (Fig 8). In mild near drowning, findings range from normal to confluent irregular perihilar areas of increased opacity in a subsegmental or segmental distribution with peripheral sparing. Pneumonia may be a complication of the aspiration of either fresh or salt water, and, depending on the water source, may be caused by a variety of microorganisms including bacteria, fungi, and mycobacteria (21–23).
Barium Aspiration
The aspiration of barium is a well-recognized complication that occurs during imaging of the gastrointestinal tract (24). Several factors may predispose to barium aspiration, including swallowing disorders and recent esophageal surgery. As with massive aspiration of gastric acid, the overall mortality rate associated with massive barium aspiration is approximately 30% and exceeds 50% in patients with initial shock or apnea, secondary pneumonia, or adult respiratory distress syndrome. Water-soluble nonionic contrast material may be the cause of significant morbidity but does not cause intense chemical pneumonitis as does water-soluble ionic contrast material. Barium aspiration in weak, debilitated patients can have serious consequences, especially with high-density barium (24,25).
Acute Exogenous Lipoid Pneumonia (Fire-eater Pneumonia)
The aspiration of massive amounts of liquid paraffin and petroleum may lead to an acute and fatal form of exogenous lipoid pneumonia (fire-eater pneumonia) (Fig 9) (26). Acute pneumonitis following aspiration of petroleum is usually related to accidental poisoning in children but is also seen in fire-eaters, who use liquid hydrocarbons such as petroleum for the flame-blowing portion of their act. The performer blows out a mouthful of liquid hydrocarbon against a burning stick, thus creating an aerosol that catches fire around the stick (26). Fire-eater pneumonia is rare but is easily diagnosed. It is characterized by pneumatoceles, or thin-walled collections of air that develop as postinflammatory lesions, often after staphylococcal pneumonia. These pneumatoceles have also been described as a late complication of hydrocarbon aspiration (27).
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Figure 9. Acute fire-eater pneumonia in a 21-year-old man who had aspirated petroleum during a performance. Posteroanterior chest radiograph shows ill-defined nodular areas of increased opacity in both lower lobes (arrows).
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Chronic Exogenous Lipoid Pneumonia
Repeated aspiration or inhalation of mineral oil or a related substance into the distal lung can lead to chronic exogenous lipoid pneumonia. In adults, the most common cause of this unusual pulmonary disorder is the use of mineral oil for the treatment of constipation and the frequent use of oily nose drops for chronic rhinitis, mainly at bedtime (5,28). These mineral oil substances introduced into the nose can easily and silently reach the bronchial tree of sleeping patients without exciting reflex inhibition. Once in the alveolar spaces, oily substances are emulsified by lung lipase, resulting in a foreign body reaction (5). A clinical diagnosis may be supported by bronchoalveolar lavage, transbronchial biopsy, or both. At histologic analysis, chronic exogenous lipoid pneumonia is characterized by numerous lipid-laden macrophages that fill and distend the alveolar walls and interstitium, where they may be associated with accumulation of lipid material, inflammatory cellular infiltration, and variable amount of fibrosis (5). In children, the condition is caused by aspiration of cod liver oil and milk (29).
CT has been reported to be the modality of choice in establishing the diagnosis of lipoid pneumonia, typically demonstrating negative attenuation values (HU < 0) (Fig 10) (30,31). Chronic endogenous accumulation of lipid material may mimic lung neoplasms. In most cases of mineral oil aspiration, the patient remains asymptomatic and the pulmonary lesion is discovered serendipitously. The "crazy-paving" pattern seen at thin-section CT has been described as characteristic of alveolar proteinosis (2). However, this pattern has been also described in association with bronchioloalveolar carcinoma (4) and, in some cases, with exogenous lipoid pneumonia (Fig 11) (5).
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Figure 10a. Lipoid pneumonia in a 56-year-old man with cough and fever who had undergone laryngectomy. (a) Posteroanterior chest radiograph demonstrates a loculated pleural collection and bilateral, ill-defined parenchymal areas of increased opacity. (b) Chest CT scan (lung window) shows ground-glass attenuation in the left lower lobe. (c) CT scan (mediastinal window) demonstrates segmental consolidation with fat attenuation values (-40 HU) in the right lower lobe (arrows). (Courtesy of Josep M. Mata, MD, Unidad Diagnóstica Alta Tecnología, Sabadell, Spain.)
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Figure 10b. Lipoid pneumonia in a 56-year-old man with cough and fever who had undergone laryngectomy. (a) Posteroanterior chest radiograph demonstrates a loculated pleural collection and bilateral, ill-defined parenchymal areas of increased opacity. (b) Chest CT scan (lung window) shows ground-glass attenuation in the left lower lobe. (c) CT scan (mediastinal window) demonstrates segmental consolidation with fat attenuation values (-40 HU) in the right lower lobe (arrows). (Courtesy of Josep M. Mata, MD, Unidad Diagnóstica Alta Tecnología, Sabadell, Spain.)
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Figure 10c. Lipoid pneumonia in a 56-year-old man with cough and fever who had undergone laryngectomy. (a) Posteroanterior chest radiograph demonstrates a loculated pleural collection and bilateral, ill-defined parenchymal areas of increased opacity. (b) Chest CT scan (lung window) shows ground-glass attenuation in the left lower lobe. (c) CT scan (mediastinal window) demonstrates segmental consolidation with fat attenuation values (-40 HU) in the right lower lobe (arrows). (Courtesy of Josep M. Mata, MD, Unidad Diagnóstica Alta Tecnología, Sabadell, Spain.)
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Figure 11. Exogenous lipoid pneumonia in a 54-year-old woman with mild dyspnea. Thin-section (2-mm-collimation) CT scan through the lung bases (lung window) shows patchy areas of increased attenuation and thickened interlobular septa in both lower lobes. Note the characteristic crazy-paving pattern. (Reprinted, with permission, from reference 5.)
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Infections
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Necrotizing Pneumonia
Aspiration pneumonia develops from a mixed bacterial infection caused by aspiration of contaminated substances from the oropharynx and gastrointestinal tract (1,32). Alcoholic patients and persons with poor oral hygiene are particularly prone to develop pulmonary infections after aspiration. Ninety percent of aspiration pneumonias are caused by anaerobic organisms (33). In hospitalized patients with colonies of highly virulent organisms, aspirations may overwhelm lung defenses, leading to the development of pneumonia (1,34). In these patients, the stomach may become colonized with gram-negative bacteria (34). Intubation and mechanical ventilation may increase the size and prevalence of aspirations with a concomitant increase in the development of pulmonary pneumonia (32,34). Radiographic findings vary somewhat among the various species of gram-negative bacilli. Chest radiographic findings in Pseudomonas aeruginosa infection typically consist of air-space areas of increased opacity in a patchy bronchopneumonic pattern; lobar air-space consolidation is much less common (34). A prolonged clinical course or large aspirations may result in severe necrotizing bronchopneumonia (Fig 12).
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Figure 12. Postaspiration necrotizing bronchopneumonia in a 53-year-old alcoholic man. CT scan demonstrates confluent alveolar areas of increased attenuation in the right lower lobe with associated cavitation (arrowheads) and pleural effusion. A small focus of aspiration is also visible in the left lower lobe.
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A distinct form of infection is caused by Actinomyces israelii, a low-virulence anaerobic bacterium that is normally found in the mouth of patients with poor oral hygiene (1). Aspiration of infected material results in a localized or lobar pneumonia, usually in the dependent portions of the lung. At radiography, the disease first appears as a localized segmental or lobar consolidation. Over a period of weeks or months after aspiration, cavitation and pleural effusion (empyema) may occur. If left untreated, actinomycosis spreads to the chest wall, mediastinum, or diaphragm.
Periodontal Disease
The oral cavity is densely populated by site-specific flora. Patients with advanced periodontal disease are at particular risk for the development of aspiration pneumonitis (33). Radiographic findings in patients with periodontal disease include focal or patchy, ill-defined lung consolidations and progressive abscess formation. The areas of increased opacity are usually unilateral but may involve both lungs (Fig 13). CT findings include multiple rounded areas of increased attenuation surrounded by a halo of ground-glass attenuation. This finding is characteristic of angioinvasive aspergillosis (35) but may also be seen with various infections and neoplasms (36).
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Figure 13a. Periodontal disease in a 42-year-old alcoholic man with fever, putrid sputum, and pyorrhea. (a) Posteroanterior chest radiograph shows bilateral, ill-defined, rounded areas of increased opacity with associated cavitation (arrowhead). (b) Thin-section CT scan demonstrates multiple solid as well as cavitary nodules. Note the presence of thick-walled cavities surrounded by ground-glass attenuation.
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Figure 13b. Periodontal disease in a 42-year-old alcoholic man with fever, putrid sputum, and pyorrhea. (a) Posteroanterior chest radiograph shows bilateral, ill-defined, rounded areas of increased opacity with associated cavitation (arrowhead). (b) Thin-section CT scan demonstrates multiple solid as well as cavitary nodules. Note the presence of thick-walled cavities surrounded by ground-glass attenuation.
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Laryngectomy
Pulmonary abscess is overwhelmingly the most likely diagnosis in patients who have undergone laryngectomy and present with a cavitary lung lesion; however, in smokers, primary squamous cell carcinoma should be considered in the differential diagnosis. At radiology, a cavitated squamous cell carcinoma may mimic a pulmonary abscess (Fig 14). In the majority of such cases, it is not possible to make a specific diagnosis because of the substantial overlap of imaging features (37). However, in the appropriate clinical setting, a reasonable differential diagnosis can be made on the basis of combined clinical and radiologic findings.
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Figure 14. Squamous cell carcinoma in a 58-year-old man who had undergone laryngectomy. Frontal radiograph shows a cavitary lesion in the posterior segment of the left upper lobe. A presumptive diagnosis of pulmonary abscess was made. Response to appropriate antibiotic therapy was poor, and surgery was performed. At histologic analysis, a cavitated squamous cell carcinoma was diagnosed.
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Other Aspiration Diseases
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Lentil Aspiration Pneumonia
Lentil aspiration pneumonia is a granulomatous pneumonitis caused by aspiration of leguminous material such as lentils, beans, and peas (38–40). Predisposing factors such as neurologic disorders, structural abnormalities of the pharynx and esophagus, emergency surgical procedures, and dementia are frequently associated with this condition (39). Lentil aspiration pneumonia typically manifests at radiography or CT as diffuse, ill-defined nodular areas of increased opacity or attenuation representing the bronchiolar distribution of the aspirated material (Fig 15). Material from repeated aspirations may appear as disseminated miliary nodules representing inflammation with foreign body reaction in bronchioles, ducts, and alveolar sacs (40). At pathologic analysis, a characteristic epithelioid granuloma with or without central necrosis in response to durable cellulose content is diagnostic.
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Figure 15a. Lentil aspiration pneumonia in a 54-year-old man with esophageal stricture. (a) Posteroanterior chest radiograph shows basilar, 3-5-mm pulmonary nodules. Biapical pleuroparenchymal areas of increased opacity are also seen, findings that are consistent with radiation changes. (b) CT scan through the upper lungs demonstrates scattered, poorly defined pulmonary nodules up to 10 mm in diameter. (c) CT scan through the lung bases shows diffuse, 1-3-mm centrilobular nodules and branching areas of increased attenuation with a "tree-in-bud" appearance. (Reprinted, with permission, from reference 40.)
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Figure 15b. Lentil aspiration pneumonia in a 54-year-old man with esophageal stricture. (a) Posteroanterior chest radiograph shows basilar, 3-5-mm pulmonary nodules. Biapical pleuroparenchymal areas of increased opacity are also seen, findings that are consistent with radiation changes. (b) CT scan through the upper lungs demonstrates scattered, poorly defined pulmonary nodules up to 10 mm in diameter. (c) CT scan through the lung bases shows diffuse, 1-3-mm centrilobular nodules and branching areas of increased attenuation with a "tree-in-bud" appearance. (Reprinted, with permission, from reference 40.)
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Figure 15c. Lentil aspiration pneumonia in a 54-year-old man with esophageal stricture. (a) Posteroanterior chest radiograph shows basilar, 3-5-mm pulmonary nodules. Biapical pleuroparenchymal areas of increased opacity are also seen, findings that are consistent with radiation changes. (b) CT scan through the upper lungs demonstrates scattered, poorly defined pulmonary nodules up to 10 mm in diameter. (c) CT scan through the lung bases shows diffuse, 1-3-mm centrilobular nodules and branching areas of increased attenuation with a "tree-in-bud" appearance. (Reprinted, with permission, from reference 40.)
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Aspiration Bronchiolitis
Diffuse aspiration bronchiolitis is characterized by chronic inflammatory reaction to repeatedly aspirated foreign particles in the bronchioles (41). Patients with esophageal conditions such as achalasia, Zenker diverticulum, or esophageal carcinoma are at risk for aspiration bronchiolitis (Fig 16) (42,43). These patients often develop moderate to marked dilatation of the esophagus with associated signs and symptoms such as dysphagia, regurgitation, and aspiration. Conventional radiographic findings are nonspecific, consisting of lobar, segmental, or disseminated small nodular shadows. At thin-section CT, aspiration bronchiolitis manifests as unilateral or bilateral foci of branching areas of increased attenuation with a tree-in-bud appearance or as mottled, poorly defined acinar areas of increased attenuation (44). Consolidation is not a major radiologic finding in aspiration bronchiolitis.
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Figure 16a. Aspiration bronchiolitis in a 68-year-old man with Zenker diverticulum. (a) CT scan demonstrates a large, posterior esophageal diverticulum in the superior mediastinum. Note the characteristic air-fluid level. (b) CT scan obtained at a lower level demonstrates multiple patchy, ill-defined parenchymal areas of increased attenuation. Note the reticular pattern of the posterobasal lesions.
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Figure 16b. Aspiration bronchiolitis in a 68-year-old man with Zenker diverticulum. (a) CT scan demonstrates a large, posterior esophageal diverticulum in the superior mediastinum. Note the characteristic air-fluid level. (b) CT scan obtained at a lower level demonstrates multiple patchy, ill-defined parenchymal areas of increased attenuation. Note the reticular pattern of the posterobasal lesions.
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At radiography and pathologic analysis, diffuse aspiration bronchiolitis resembles diffuse panbronchiolitis (Fig 17). Complete healing of bronchiolar inflammation may occur.
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Figure 17. Diffuse aspiration bronchiolitis in a 61-year-old woman with achalasia and recurrent aspiration of foreign particles. Thin-section CT scan shows multiple diffuse centrilobular areas of increased attenuation with a characteristic tree-in-bud appearance. Esophageal dilatation with an air-fluid level is also seen.
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Obliterative Bronchiolitis
A significant number of patients with chronic bronchitis have gastrointestinal reflux (19), and there is some evidence to suggest an association between reflux and asthma (45). Intermittent microaspirative phenomena could produce mucosal injury of bronchioles and subsequent airflow obstruction. Gastroesophageal reflux and aspiration have been considered predisposing factors in the development of obliterative bronchiolitis. Thin-section CT findings associated with obliterative bronchiolitis include bronchial dilatation, mosaic perfusion, bronchial wall thickening, and air trapping (44). Of these findings, air trapping and bronchial dilatation appear to be the most sensitive and specific in the detection of this disease entity (Fig 18).
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Figure 18a. Gastric aspiration and constrictive bronchiolitis in a 68-year-old woman with achalasia. (a) Posteroanterior chest radiograph shows a hyperlucent zone in the right lower lobe with associated volume loss and a reduced number of lung vessels (arrowheads). (b) Prone expiratory CT scan shows decreased attenuation in the right lower lobe. The size and number of vessels are reduced. These findings are consistent with the presence of bronchiolar inflammatory disease with air trapping.
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Figure 18b. Gastric aspiration and constrictive bronchiolitis in a 68-year-old woman with achalasia. (a) Posteroanterior chest radiograph shows a hyperlucent zone in the right lower lobe with associated volume loss and a reduced number of lung vessels (arrowheads). (b) Prone expiratory CT scan shows decreased attenuation in the right lower lobe. The size and number of vessels are reduced. These findings are consistent with the presence of bronchiolar inflammatory disease with air trapping.
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Conclusions
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The radiologist plays a major role in the definitive diagnosis of various complications of pulmonary aspiration. The relatively low diagnostic accuracy of chest radiography can be improved by being familiar with the clinical settings in which specific complications are likely to occur. Knowledge of the varied radiographic appearances of aspiration diseases should improve recognition of pulmonary disorders associated with aspiration, several of which can be life-threatening and require prompt diagnosis. When radiographic findings are subtle or equivocal, CT frequently allows identification of the disease process.
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Abstract
Introduction
