My Son Is 24 Years Old. He Was Born With

My son is 24 years old. He was born with a HPRT deficiency ( Lesch Nyhan Syndrome Variant). He recently had to have emergency surgery for a 6mm stone obstructing his ureter. There was a additional 6mm stone in his kidney. They put a stent in last Monday 8/3 and is removing it tommorrow 8/14. His creatinine at the time of surgery was 3.2. When he left the hospital on 8/5 it was 2.89. He has to have the stent removed tommorrow. His creatinine is now 1.84. I know he has this rare condition and he for the longest time refused to take his medicine. My other son has the same syndrome and takes 900mg of allopurinol. His kidneys seem to be fine in spite of the stones that he still gets. Tom is now on 80 mg of uloric. His primary Dr. said that too much allopurinol is not good for his kidneys, thats why he put him on urloric. Allopurinol gets filtered thru the kidneys and urloric gets filtered thru the liver. I am just worried sick that I read too much and what I'm reading is a creatinine level of 1.84 is already in the 3rd stage renal disease. Am I over exaggerating or is this the real thing?