My three year old has been suffering from constipation On and off for a couple of weeks now. During the day today he kept telling me that there was something wet in his underwear and I thought he was having a bit of diarrhea when he passed gas, it turns out that it s actually white foam coming out of his anus. He had a BM tonight and when he was done he passed gas with a lot more white foam. I am calling his Dr. In the morning to schedule an appointment, but I would like to put my mind at ease tonight. What could this be?