From just a quick google search.
From http://www.rxlist.com/cgi/generic/ibup_cp.htm
“Ibuprofen is rapidly metabolized and eliminated in the urine. The excretion of ibuprofen is virtually complete 24 hours after the last dose. The serum half-life is 1.8 to 2.0 hours.”
This is exactly what I am refering. If this article is read, they do not say the kidneys metabolize ibuprofen. They merely say it is metabolized (i.e. in general). Someone with medical knowledge knows that it would pass through the liver first, become metabolized, then passed to the kidneys. And actually, the article refers mainly to what you missed, and I mentioned as primary reason for concern: ulceration.
Here is the original link where I said exactly this.
Mantaray