Hello, i would like to understand what exactly not clinically significant means with regard to a small pericardial effusion. ?

Significance: The pericardial sac encapsulates the heart. If an effusion as small, it is not enough to interfere with the mechanical work of the heart, thus clinically insignificant. If it is large, it can impinge on the walls of the heart, forcing them in and limiting the volume of blood they can pump. The significance determines how aggressive they would be to remove the fluid with a needle or operation.

Not clinically sig: Means an incidental finding or observation that is insignificant or is unrelated to why a test was ordered and usually has no effect on body functions. Normally there is some pericardial fluid that acts like a lubricant for the heart to move. Lg amt can restrict heart function.