Tour de France 2010

There's a story in Kimmage's book 'A Rough Ride', there's an incident he describes in the '86 Tour which may answer your question. He recounts that during one transition stage, he noticed Lemond being brought up to the front by his domestiques, and that Lemond was clearly suffering from diarrhea, the results of which were streaming down Lemond's legs.

There is a story about a domestique riding for Simpson who was wearing a smart new cap of which he was very proud being called over by Simpson who asked for his cap. He reluctantly handed it over only to see Simpson take a dump in it and then pass it back.