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A 33-year-old woman is evaluated for progressive dyspnea. She has smoked 1 pack of cigarettes per day for 18 years. She has no constitutional symptoms or significant environmental exposures. She had a small pneumothorax 3 year ago treated with simple drainage. On physical examination, she has a prolonged expiratory phase and few basilar crackles in both lower lobes. Cardiovascular examination is normal. She has trace edema of the lower extremities. Chest radiograph shows a subtle reticulonodular infiltrate. Lung function studies show forced expiratory volume in 1 sec (FEV1) 60% of predicted, forced vital capacity (FVC) 75% of predicted, and FEV1/FVC ratio of 60%, and diffusing lung capacity for carbon monoxide (DLCO) is 55% of predicted.
What is the most important next step in this patient's evaluation?
A Methacholine challenge
B Cardiac stress test
C HRCT scan of the chest
D Bronchoscopy
E Ventilation/perfusion scan
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Correct Answer = C)
Key Point
High-resolution computed tomographic scanning (HRCT) is more sensitive than plain chest radiography for detecting interstitial lung disease and more specific for the potential diagnoses.
This patient's presentation suggests interstitial lung disease with an abnormal auscultatory examination, a diffusely abnormal chest radiograph, and an obstructive physiologic defect with a low diffusing capacity. High-resolution computed tomographic scanning (HRCT) is more sensitive than plain chest radiography in identifying the presence of interstitial lung disease as well as more specific when it comes to providing the potential diagnoses. In the correct clinical setting, distinctive radiographic patterns aid in identifying the underlying diagnosis especially when changes on HRCT show characteristic patterns such as diffuse cystic disease (as in lymphangioleiomyomatosis), or the combination of cysts and nodules (such as in pulmonary Langerhans' cell histiocytosis). Other patterns can also be characteristic such as that of established lung fibrosis (honeycomb change and traction bronchiectasis). In this patient the sex, smoking history, previous pneumothorax, chest radiograph, and pulmonary physiology are all potentially relevant.
Methacholine challenge helps identify occult reversible airflow limitation. However, although asthma could explain this patient's symptoms, the presence of the abnormal parenchyma on the chest radiograph and the low DLCO both argue against asthma as the diagnosis. The same concerns hold true for the cardiac stress test and ventilation-perfusion scanning. Although cardiac disease or pulmonary embolus could explain the symptoms, the previous pneumothorax, abnormal chest radiograph, and pulmonary physiology all more strongly suggest an interstitial lung disease as the cause. When a definitive pathologic diagnosis is required in diffuse lung disease, bronchoscopic biopsy specimens can be useful but are rarely of adequate size to make a positive diagnosis and a surgical lung biopsy is generally necessary.
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nice rhyming name.....welcome to forum
