Hello, my 15 month old son has had a high fever (now under control) since Sunday. We took him to the ER Sunday and they ran some tests. White blood count was a little higher than normal, but not alarming according to doc. They did a chest xray and saw a retrocardiac opacity in the left lung . They could not tell whether it was pneumonia , so they treated it as such as a precautionary measure. He also had been diagnosed with pneumonia last December, as they saw small opacities in both lungs. The doctor wants us to bring him in in a month to redo the chest xray because the left retrocardiac opacity seems to be close to the area of the last spot seen in the xray last December. The right spot (from Dec.) is no longer there. I want to add besides these two incidents, my son has been very healthy, growing fine, meeting developmental milestones and is otherwise in great health. Even with this instance, he was barely coughing which made me question their diagnosis of pneumonia. My question is what could the left retrocardiac opacity mean? Could it be the same one from December?