I do not think it would be highlighted whether it was a professional athlete, or anyone else for that matter. Maybe one of the home video/comedy shows might highlight it, but I really don't think that's "news". I personally would have no interest in seeing something like that,
NASCAR drivers do this all the time. Actually it was rumored a few years ago that Tony Stewart, while driving sick, exited the car and had a replacement driver come in mid race because he had diarrhea on himself. No one thinks much of it. The media said nothing about it. It was lightly discussed in forums but that was it. I think that when it comes down to it we all remember these people are human and are usually putting their bodies through more than they should.
Oh wow. I did not know that. Wen you think about it it makes perfect sense though. I think even the small chatter on the forums about him being sick was probably more in concern for why he didn't finish driving. Good answers.
The marathon runner Paula Radcliffe had to stop and wee once by the side of the road, mid race. She just squatted right there, just behind one of the two feet tall barriers, on the pavement. The commentators as I remember were polite about it, and the camera neither lingered nor moved on too quickly. Not sure what that did to her race time :-)) but at least it shows she wasn't dehydrated.