All B-lines are equal, but some B-lines are more equal than others.

In this pictorial essay the theme of the differential diagnosis between the different causes of lung interstitial disease will be discussed, which can be detected on lung ultrasound as B lines. In particular, from the experience obtained during the covid-19 pandemic, the term B line may appear too simplified, and new data in the literature show that it is necessary to update the terminology and the differential diagnosis of this ultrasound sign.