B lines do not always indicate pulmonary edema
Diffuse B-line pattern can be seen in pulmonary edema of various causes, interstitial pneumonia and diffuse parenchymal lung disease (e.g. fibrosis). Whether you are dealing with pulmonary edema or fibrosis largely depends on the clinical context. However, findings such as irregular, fragmented pleural line, sub pleural abnormalities appearing as small hypoechoic areas and nonhomogeneous distribution of B-lines favor fibrosis. On the other hand, “focal” B-line pattern may be seen in pneumonia, atelectasis, pulmonary contusion, pulmonary embolism, pleural disease and malignancy.
The following loops were obtained from upper anterior zones on each side (R/L). While they show B-line pattern, the lower lung zones were normal and the patient was breathing comfortably on room air. This is a patient with interstitial lung disease and the B-line pattern represents fibrotic process. Also note that the pleural line is irregular.