Actually the upper GI/small bowel secretes the fluids, for digestion purposes, and the large bowel/colon is supposed to absorb it back up in a healthy body....in a person with small bowel Crohns only, they get problems with malnutrition because nutrients are primarily absorbed there...in a person with large bowel Crohns only, diarrhea is an issue because it's too inflammed to absorb the said fluids (but malnutrition isn't as big of a problem because this assumption is that the small bowel is fine, large bowel isn't, still restrictive diet can cause nutrient issues)...in rectal Crohns, the urgency is a major issue (accidents), so when rectal AND colon-specific Crohns is present, you get MAJOR urgency/diarrhea issues (this is me)....
Refer to what I said for your Crohns to find your disease's propensities, the characteristics are a big help for coping.
I echo D Bergy's posts. Could be a fluke Hippie, refer to what you ate 24 hours prior.