High creatinine excretion levels are going to go hand in hand with creatine supplementation. Personally I don't think its anything to be worried about... A percentage of the creatine you're ingesting is going to change to creatinine just by passing through the digestive system.
If you have a history of liver-kidney issues then i'd be cautious, but from what i've read creatine shouldn't be harmful in itself. A lot of the "organ damage" cases "caused" by creatine IMO are product adulteration (mostly heavy metals) by improper manufacturing procedures (mostly from oversea sources lacking poor quality control).
The science is still out on how safe long term supplementing is, but i've seen two recent studies, one with Div I football players, that have run up to ~3 years with no ill effects. Of course I'm remembering this off the top of my head so I could be mistaken. I also seen theories stating creatine supplementation increases kidney metabolite excretion rather then production, the higher markers being what scientists initially assumed was due to kidney stress.