What Causes Swelling Around The Eyes?

My son is 16. He has been having face swelling around his eyes for some time now. He s also been very fatigue! We been to our pediatrician several times and an allergy dr. No ones been able to tell us anything! This week he woke up several days with the right eye swollen shut! We went back to the pediatrician and she did some more test. They called today and said his sodium levels came back high and has us come in for more blood work. I remembered that I forgot to mention that his pee has been really dark and foamy! She wasn t there when we went back for blood work so I ve yet to mention this.