Fluid around heart due to kidney failure... will ekg show abnormalities?

Pericardial Effusion: If you are talking about a pericardial effusion, fluid in the pericardium which surrounds the heart, a better test to diagnose this is an echocardiogram. This will give an estimate of the fluid found there. An ekg can show low voltage, but that is not diagnostic of a pericardial effusion. A chest x-ray will show an enlarged heart. You will still an echocardiogram to see how much fluid is present.

Maybe: Although there are a number of nonspecific changes on ekg an echocardiogram would be the definitive test.

Yes: Yes, it can. Typically we look for low voltage ekg for fluid accumulation. And if pericardium (memebrane around heart) is inflammed it can have diffuse st ( one segment of ekg ) elevation.