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2. Increased pressure edema
Given that extensive interlobular septal thickening is present, the one entity among those listed that often results in interlobular septal thickening at thoracic imaging studies is increased pressure edema (also often referred to as hydrostatic pulmonary edema, or less specifically, cardiogenic pulmonary edema). Lymphangioleiomyomatosis (LAM) is a form of cystic lung disease, but occasionally can show a somewhat linear pattern at chest radiography owing to partial visualization of cysts walls; however, even this appearance of LAM is generally not confused with interlobular septal thickening. Usual interstitial pneumonia may occasionally produce some interlobular septal thickening, but the dominant picture is usually that of basal and peripheral reticulation associated with low lung volumes, occasionally even visualization of discrete honeycombing. Pneumonia due to Streptococcus pneumoniae commonly causes a “lobar pneumonia” pattern, but may also produce segmental consolidation typical of the bronchopneumonia pattern. An “interstitial” appearance for this infection is unusual, and, even when interstitial opacities are present in patients with pneumococcus, the interlobular septal thickening would not be as profound as it is in this patient. The chest radiographic findings of chronic hypersensitivity pneumonitis are ultimately nonspecific, but generally appear as bilateral mid- and upper lung coarse linear and reticular abnormalities, representing fibrosis, associated with areas of architectural distortion, not the fairly diffuse, symmetric interlobular septal thickening, unassociated with distortion, as seen in this patient.
The chest radiographic findings (cardiomegaly and interlobular septal thickening) and patient’s new shortness of breath raised the possibility of increased pressure edema, so the patient was begun on diuretic therapy. Chest radiography was repeated 6 days later (Figure 2).
Figure 2. Frontal (A) and lateral (chest radiography performed 6 days after presentation.
Which of the following represents the most accurate interpretation of the repeat chest radiographic findings? (Click on the correct answer to proceed to the fifth of eight pages)