High Creatine Level

My boyfriend had suffered a stroke, well that is what they believe happened. But anyway his kidneys had stopped working and he has a high level of creatine..7.0(now) was higher. He had never had kidney problems before this, they have started working in the sense that he is urinating now about 4 times a day, I believe he said 500ml or something like that. Even though he is urinating his creatine is still at 7, why would that be. They said two other levels they check are good but the creatine is not. Why would that be and why would he still be on a renal diet? Why is dark sodas not good for you when your creatine is high and is there anything he can do to get that number down?