This has been a slight problem for me for the past year, Valencia marathon in November lost five or six minutes waiting for a loo.
Started running trails / off road this year and boy the problem has become ten fold worse. This morning was fairly typical, try as I might, no chance of going beforehand 6 to 6:30, two miles into the run and the bushes are thee only option. Five miles later and desperate to go again. Small upside is being offroad the bushes option is far easier than if I were pounding the roads!
The actual output seems really healthy, not diarrhoea like in any way, but the amount is frightening. Probably goes cap in hand with a massive increase in what I eat on a daily basis since going off road and upping the miles.
Seriously starting to feel guilty about the amount I am leaving around the locality!!