Trivial amount of fluid around heart -causes?

Probably normal: The heart lies with in the pericaridal sac. This is bag formed by a fairly strong membranous tissue. There is always a small amount of fluid in the pericardium probably for lubrication. It's called pericarial fluid. This is normal. Sometimes the fluid level can increase this is called a pericaridal effusion. This can be caused by infection, heart failure, kidney disease, and trauma.