Differentials
Acute respiratory distress syndrome
SIGNS / SYMPTOMS
Seen in the setting of sepsis, chemical exposure, drug reactions, toxic inhalation, or trauma. No difference in signs and symptoms from aspiration pneumonitis, which can itself lead to acute respiratory distress syndrome.[80]
INVESTIGATIONS
Bilateral alveolar infiltrates can be indistinguishable from those seen in aspiration pneumonitis.
Aspiration pneumonitis is usually distinguished from aspiration pneumonia on the history of a witnessed large-volume aspiration. In aspiration pneumonitis, the patient often has a reduced level of consciousness.
Asthma exacerbation
SIGNS / SYMPTOMS
Wheezing is paroxysmal and intermittent and usually diffuse. It decreases after bronchodilators, is polyphonic, and is characterized by many different pitches. Cough is triggered by exercise, cold, sleep, and allergens. Patient may have history and/or family history of atopy or asthma.[81]
INVESTIGATIONS
Pulmonary function tests usually show reversible obstructive ventilatory impairment.[81]
Cystic fibrosis with exacerbation
SIGNS / SYMPTOMS
Wheezing presents early in life, with accompanying poor weight gain, diarrhea, and recurrent sinus and pulmonary infections. Nasal exam may reveal polyps. Cough is productive and wet, suggesting a suppurative process such as bronchiectasis. Patient may have family history of bronchiectasis.[81]
INVESTIGATIONS
Sweat chloride test shows elevated level of chloride. Chest x-ray may reveal bronchiectasis, but CT scan is more sensitive.[82]
COPD exacerbation
SIGNS / SYMPTOMS
Wheezing is diffuse and associated with increased mucus production and history of progressive dyspnea.
INVESTIGATIONS
Chest x-ray shows peribronchial cuffing and hyperinflation.
Community-acquired pneumonia
SIGNS / SYMPTOMS
No difference in signs and symptoms.
INVESTIGATIONS
Chest x-ray may show lobar consolidation.
Hospital-acquired pneumonia
SIGNS / SYMPTOMS
No difference in signs and symptoms.
INVESTIGATIONS
Chest x-ray may show lobar consolidation.
Congestive heart failure
SIGNS / SYMPTOMS
Orthopnea, paroxysmal nocturnal dyspnea, and right upper quadrant discomfort may be features. Sputum, if present, is usually frothy. Fever is usually absent.[83]
The third heart sound gallop rhythm has up to 50% sensitivity but 90% specificity. Pulsus alternans, characterized by evenly spaced strong and weak peripheral pulses, is pathognomonic of severe left ventricular failure.[83][84]
INVESTIGATIONS
Chest x-ray may reveal enlarged pulmonary vessels, cardiomegaly, and pulmonary edema; the infiltrates improve quickly after diuresis.
Brain natriuretic peptide >100 picograms/mL makes a diagnosis of heart failure with sensitivity of 90%, specificity of 76%, and predictive accuracy of 83%.[85]
Acute exacerbation of interstitial lung disease (ILD)
SIGNS / SYMPTOMS
No differentiating symptoms or signs, but they develop over a few days to several weeks. In some cases it is idiopathic (Hamman-Rich syndrome) or related to other ILD including idiopathic pulmonary fibrosis.[75] Some connective tissue disease-ILDs such as systemic sclerosis are prone to esophageal dysmotility and consequent reflux and aspiration. Drug and radiation toxicity should also be considered in the appropriate clinical context.
INVESTIGATIONS
Bilateral alveolar infiltrates can be indistinguishable from those seen in aspiration pneumonitis or acute respiratory distress syndrome (ARDS). However, evidence of background fibrotic lung disease such as honeycombing may be present. Comparison to prior imaging when available is critical.
Bronchoalveolar lavage cell count reveals >10% neutrophils, and lung biopsy shows diffuse alveolar damage.[75]
Acute bronchiolitis obliterans organizing pneumonia
SIGNS / SYMPTOMS
No differentiating symptoms or signs. Can be idiopathic or due to collagen vascular disorders, drugs, radiation, or infection.[75]
INVESTIGATIONS
Bilateral alveolar infiltrates can be indistinguishable from those seen in aspiration pneumonitis. Bronchoalveolar lavage cell count in organizing pneumonia may reveal neutrophilia and sometimes lymphocytosis (but <25% lymphocytes) with eosinophilia (but <25% eosinophils).[75]
Acute eosinophilic pneumonia
SIGNS / SYMPTOMS
No differentiating symptoms or signs, but duration of illness is usually <1 week. Can be idiopathic or caused by drugs.[75]
INVESTIGATIONS
Bilateral alveolar infiltrates can be indistinguishable from those seen in aspiration pneumonitis. Bronchoalveolar lavage cell count reveals >25% eosinophils. Eosinophilic pleural effusion is rare. Eosinophilic infiltration and diffuse alveolar damage may be seen on lung biopsy.[86]
Acute hypersensitivity pneumonitis
SIGNS / SYMPTOMS
No differentiating symptoms or signs, but usually develops within 4-6 hours after inhalation of an organic agent. Caused by environmental and work-related antigens.[75]
INVESTIGATIONS
Bilateral alveolar infiltrates can be indistinguishable from those of aspiration pneumonitis. Granulomatous and cellular pneumonitis with diffuse alveolar damage may be seen on lung biopsy. Bronchoalveolar lavage cell count shows lymphocytosis (>25%) and sometimes neutrophilia (<10%).[75]
Diffuse alveolar hemorrhage
SIGNS / SYMPTOMS
Hemoptysis is absent in 33% of patients. Causes include vasculitis, collagen vascular disorders, antibasement membrane antibody disease, coagulopathies, antiphospholipid antibody syndrome, and diffuse infections.[75]
INVESTIGATIONS
Bilateral alveolar infiltrates can be indistinguishable from those of aspiration pneumonitis. Pulmonary capillaritis, bland hemorrhage, and diffuse alveolar damage seen on lung biopsy.
Bronchoalveolar lavage shows progressively bloodier return. Cytology shows red blood cells and hemosiderin-laden macrophages.
Urinalysis may show proteinuria, hematuria, and red cell casts in cases of pulmonary-renal syndromes.[75]
Neurogenic pulmonary edema
SIGNS / SYMPTOMS
No differentiating symptoms or signs. Usually develops within minutes to hours after acute central nervous system injury such as seizures, head injury, or cerebral hemorrhage. Resolves within 48-72 hours.[87]
INVESTIGATIONS
Bilateral alveolar infiltrates may be indistinguishable from those seen in aspiration pneumonitis.[87]
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