I need help for a friend...?

he has FREQUENT diarrhea or i guess more like SOFT stool...for instance this mornin before he left for work he used the bathroom 3 times and by the time he got to work he had messed his pants because he could not hold it. he says it has a grey color and a VERY foul smell. some mornings he wakes up and feels like his insides are on fire it burns so bad but he is not in PAIN...someone said they believe it is his gall bladder...any suggestions....he also poops like this when he doesnt eat. the other day he ate TWO crackers and was on the toilet for 15 minutes