I just got results from a chest xray
The him is the part of the lung where the blood vessels and airways enter the lung. In that region there are also structures called lymph nodes, which are collections of white blood cells that are part of our immune system. Hilary fullness can be caused by enlargement of the structures in the him. Most commonly this is due to enlargement of the lymph nodes by infections. Unfortunately often the exact cause is not evident on a chest x-ray and thus a CT scan of the chest may be required to better assess the Hilary fullness. I hope this provides you some clarity.