Diffuse B-line pattern can be seen in pulmonary edema of various causes, interstitial pneumonia, diffuse parenchymal lung disease (e.g. fibrosis), ARDS etc. Whether you are dealing with cardiogenic pulmonary edema or others largely depends on the clinical context and interpreting in conjunction with echocardiography. However, findings such as irregular, fragmented pleural line, sub-pleural abnormalities appearing as small hypoechoic areas and non-homogeneous distribution of B-lines favor pneumogenic etiology. “Focal” B-line pattern may be seen in pneumonia, atelectasis, pulmonary contusion, pulmonary embolism, pleural disease and malignancy. Moreover, a few B-lines in dependent zones (typically <3 per rib interspace) can be physiologic, especially in elderly patients.

The following clips 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.

Here’s another example: these images are from a patient with an underlying malignancy and diffuse pulmonary nodules. You can see the confluent B-lines, an irregular pleural line, and a small subpleural consolidation (obtained with a linear probe to get a closer look at the pleura). Lung ultrasound can certainly reduce the need for repeated chest X-rays when monitoring congestion, but when you’re dealing with underlying pulmonary pathology, having a baseline X-ray or CT for comparison still makes a big difference.

One more example from a patient with patchy lung scarring. At the time of obtaining these images, patient was comfortable on room air. Despite having pulmonary hypertension at baseline, IVC was small and collapsible (s/p diuresis). Note spared areas – some rib interspaces with A-lines and some with B-lines. Those with B-lines demonstrate irregular pleural line.

Below are images obtained from a dialysis patient with fever. Right lateral zones show confluent B-lines, irregular pleural interface and notable subpleural consolidation (arrows). This is suggestive of pneumonia.

Here is an infographic reminding the non-specific nature of B-lines.