Decreased pulmonary vascularity?

My son was born with right sided Congenital Diaphragmatic Hernia we had x rays a couple of days ago and the dr said that the xrays show decreased vasculartiy in his right lung. Does anyone know what this means? He was born with one and a half lungs and we are going to see a pulmoniligist soon to find out more but we are wondering what this means for our son. He is 7 now and this is the first major problem we've had since an asthma attack at 9 months old . thanks for any help!