Preliminary Diagnosis: Toxic lung injury (Silo-Filler's disease)
I. What imaging technique is first-line for this diagnosis
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Chest radiographs (CXR) with posteroanterior (PA) and lateral projections
II. Describe the advantages and disadvantages of this technique for diagnosis of toxic lung injury (Silo-Filler's disease).
Advantages
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Diagnostic for the noncardiogenic edema seen with toxic lung injury (TLI)
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Exposes the patient to less ionizing radiation than computed tomography (CT) of the chest
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Serial chest radiographs are sufficient to follow the course of TLI
Disadvantages
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Initial CXR can be negative as the noncardiogenic edema of TLI appears anytime from immediately to 48 hours after injury (usually by 6 hours)
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Less sensitive for other types of thoracic disease, such as associated trauma
III. What are the contraindications for the first-line imaging technique?
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CXR has no significant contraindication
IV. What alternative imaging techniques are available?
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High resolution CT (HRCT) chest without contrast
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CT chest with intravenous contrast
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CT chest without contrast
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Ventilation perfusion (V/Q) scan
V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of toxic lung injury (Silo-Filler's disease).
High resolution CT chest without contrast
Advantages
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Diagnostic of TLI
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Best alternative study in the scenario of unexplained chronic dyspnea and non-diagnostic chest radiography
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Most capable study for diagnosis of any diffuse lung disease (i.e., hypersensitivity pneumonitis, interstitial lung disease, etc.)
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HRCT with inspiratory and expiratory images can document air trapping, sometimes present in TLI
Disadvantages
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HRCT performed without contrast is non-diagnostic for pulmonary thromboembolism (PTE)
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More expensive and time-consuming, and exposes the patient to more ionizing radiation than chest radiography
CT chest with intravenous contrast
Advantages
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Diagnostic of TLI
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Best alternative study if there is also concern for traumatic thoracic injury
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Appropriate alternative if infection or malignancy are other diagnostic considerations
Disadvantages
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The contrast dose administered may have to be reduced or withheld if the patient has decreased renal function
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Patients with known allergic reaction to iodinated contrast must undergo pre-treatment with steroids and anti-histamines for at least 13 hours prior to contrast dose, or have contrast withheld
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Exposes the patient to ionizing radiation
CT chest without contrast
Advantages
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Diagnostic of TLI
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Can show other thoracic disease processes, including traumatic injury
Disadvantages
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Exposes the patient to ionizing radiation
Ventilation perfusion (V/Q) scan
Advantages
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V/Q scan can show air trapping or delayed radiotracer washout typical of TLI, even in the setting of negative CXR
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V/Q scan can be diagnostic of PTE
Disadvantages
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Less readily available and more time-consuming than CXR or CT
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Exposes the patient to ionizing radiation
VI. What are the contraindications for the alternative imaging techniques?
High resolution CT chest without contrast
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Patients unable to remain motionless and hold their breath for up to 25 seconds during the test will have images degraded by motion artifact
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Contraindicated in pregnant women, especially in the first and second trimesters
CT chest with intravenous contrast
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The contrast dose administered may have to be reduced or withheld if the patient has decreased renal function
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Patients with known allergic reaction to iodinated contrast must undergo pre-treatment with steroids and anti-histamines for at least 13 hours prior to contrast dose, or have contrast withheld
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Contraindicated in pregnant women, especially in the first and second trimesters
CT chest without contrast
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Contraindicated in pregnant women, especially in the first and second trimesters
Ventilation perfusion (V/Q) scan
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V/Q scan has no absolute contraindication
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V/Q scan is not recommended for patients for whom there is high suspicion of massive PTE
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Relative contraindications of V/Q scan include severe asthma, COPD, or cystic fibrosis
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