"HELP!!! Yesterday my daughter's legs swelled up. She is 4 months old.…

"HELP!!! Yesterday my daughter's legs swelled up. She is 4 months old. We called a doctor who examined her and said to have blood tests (OAK, OAM), all results were normal. They said that this could be due to a viral infection, we caught the flu now we are being treated. But I don't understand why? Doctors say nothing, has anyone had this?"