Is there a lot of undigested food in it? If so, it does sound like what Snowy Love is talking about.

My DS was diagnosed with this & we had to increase the fat in his diet & reduce the amount of juices & that sort of thing. What happens is that their intestines move the food through too quickly & there's not enough time for the water to be absorbed out. Our paed suggest adding extra butter to sandwiches, introducing nutella & peanut butter (because of the oils) and to allow him to have hot chips at least once a week. Sounds insane right? But in explaining he said that for us that sort of food is bad because we are more sedentary, but for kids they run the energy off so it's ok for them to have fatty foods a bit more often.