from morons.org:

According to reports in the Austrian press, during a recent visit by President Bush to Vienna, the White House sent along a portable toilet for the commander in chief's personal use. Bush's precious bodily fluids were reportedly collected and flown back to the United States to prevent them falling into enemy hands. Portapotty One was also stocked with toilet paper flown in from a US base in Ramstein, Germany.

I would venture a guess that the procedure would be intended to prevent testing to determine what drugs/alcohol the Prez is ingesting. Or should, but isn't.