What's a 'urine manipulator'? In a sports medicine, illegal supplement context?

The Chicago Tribune, in today’s story on a Northwestern U. football player who died August 3, says this about NCAA drug testing:
http://www.chicagotribune.com/news/local/chi-0108240328aug24.story?coll=chi-news-hed

So, what’s a “urine manipulator”? Nothing comes up on Google. It can’t be a proper noun, as in “people who manipulate their urine”, because the other direct objects in the sentence are “diuretics” and “steroids”, neither of which means “people”, either.

Does it mean “something you put into your urine sample to confuse the test”? But wouldn’t practically anything do that, like Kool-Aid or sewing machine oil, so does “testing for urine manipulators” mean they’re just testing for “anything that isn’t urine”? Or what? Can they do that, with all the hundreds of things you could put into your urine sample?

Or did Mike and Todd just mean to say something else? :confused:

I don’t hang out with people who know about urine tests, as so far neither the U.S. Postal Service nor the local school district is requiring them. :smiley:

I’ve never heard that term, but I would think that “urine manipulators” refers to masking agents used to hide evidence to illegal substances. Some substances are banned not because they are performance enhanching but because they are specifically used to mask the usage of other banned substances. It goes a little beyond merely confusing the test, which could result in an invalid sample or failed test.