From the Guidelines
In cases of severe diffusion defect but normal lung CT scan, pulmonary vascular diseases, such as pulmonary embolism or pulmonary hypertension, are likely underlying causes 1.
Key Considerations
- Further evaluation with echocardiogram, pulmonary angiogram, or right heart catheterization may be necessary to confirm the diagnosis 1.
- A ventilation-perfusion scan should be ordered to assess for any mismatch, as it has higher sensitivity compared to CT pulmonary angiogram (CTPA) in detecting chronic thromboembolic pulmonary hypertension (CTEPH) 1.
Management
- If pulmonary embolism is suspected, anticoagulation with heparin or low molecular weight heparin may be initiated 1.
- For pulmonary hypertension, medications like sildenafil or bosentan may be considered 1.
- It is essential to monitor oxygen saturation and adjust supplemental oxygen therapy as needed to maintain saturation above 90% 1.
- Close follow-up with a pulmonologist or cardiologist is recommended to adjust the treatment plan according to the underlying diagnosis and clinical response 1.
Additional Diagnostic Considerations
- High-resolution CT of the chest may be considered to identify the presence of group 2 (left heart disease) or group 3 (lung diseases) pulmonary hypertension 1.
- Lung function tests, including DLCO, are recommended in the initial evaluation of patients with pulmonary hypertension 1.
From the Research
Severe Diffusion Defect with Normal Lung CT Scan
- A severe diffusion defect with a normal lung Computed Tomography (CT) scan can be caused by various pulmonary vascular diseases, including pulmonary embolism, chronic thromboembolic pulmonary hypertension (CTEPH), and pulmonary arterial hypertension 2.
- Pulmonary embolism can cause a reduction in diffusing capacity of the lung, which may persist even after anticoagulation treatment and normalization of lung scans 3.
- Chronic thromboembolic pulmonary hypertension (CTEPH) can also cause a severe diffusion defect, and ventilation-perfusion scanning is recommended for excluding CTEPH during the diagnosis of pulmonary hypertension (PH) 4.
- Pulmonary arterial hypertension may be idiopathic or arise in association with various conditions, including chronic pulmonary thromboembolism, and its histologic characteristics include vascular changes that manifest primarily in the muscular pulmonary arteries 5.
- A normal lung CT scan does not necessarily rule out pulmonary vascular diseases, as some conditions may not be visible on CT scans, and other diagnostic tests such as ventilation-perfusion scanning may be necessary to diagnose these conditions 4, 2, 5.