It is impossible to say what exactly a doctor might mean when he talks about a shadow in the liver. There are a multitude of possibilities and only further tests will be able to reveal what are the causes of a shadow on the liver are.
The best thing to do is to speak to the doctor and ask him to explain in detail what he thinks the shadow might be and what he intends to do to find out, if he does not know what it is.
Unfortunately, many doctors have an infuriating attitude when it comes to telling patients what is going on. They will make some sort of statement, and then glibly add that there is nothing to worry about. Then they leave the patient in the dark for weeks on end.
In the meantime, the patient makes him or herself more ill with all sorts of fears and worries. Why doctors do this is anybody's guess. Speaking from experience, it appears that they do not wish to worry the patient until they have discovered the cause of a problem.
Unfortunately, things do not quite work like that and doctors need to be made aware of the fact that patients are far less likely to worry if they are kept informed. There really is nothing worse than not knowing what is happening, and why.
We do not have the medical knowledge to even make an educated guess at what a shadow in the liver might mean. We therefore have to restrict our advice to telling anyone who has been told they have a shadow in their liver to go to their doctor and insist on being told exactly what the possibilities are, and what will be done to find out and deal with the cause.