Hydronephrosis

My son was born with Grade 5 urinary reflux. At 7 days old he had surgery to remove a blockage in his urethra. He continued to have grade 4 reflux. When he was 3 years old he had bilateral reimplantation of the ureters. We also found an atrophic right kidney. He still has moderate hydronephorsis on his "good" left kidney. His urologist isn't concerned about this. We just saw him last week and wants to see us again in one year with another renal ultrasound. Daddy and I are concerned about waiting that long and wondering if we are damaging his only kidney. Creatine is always hovering at 0.4 and BUN is usually high 20's.