To dream of a diarrhea represents a sense of urgency to deal with a problem that sidetracks you from your real goals. Feelings about how terrible it is to be forced to cleanse something from your life. Removing something negative from your life faster than you feel comfortable with. You may be feeling a lack of control over how a problem is confronted. An urgent need to deal with a problem quickly and completely.
Negatively, diarrhea may reflect feelings about an embarrassment never stopping. Feeling uncomfortable having to get rid of a problem. Issues in waking life that make you feel stupid for believing that they weren't going to be serious or have consequences. Urgency to avoid looking guilty or cover up your guilt. Regretting indulging or enjoying yourself too much. A fear of humiliating yourself looking like novice or inexperienced idiot. Embarrassment of having to face your problems harder than anyone else.
Positively, dreaming about diarrhea may reflect feelings about your choice to uncomfortably get rid of a problem faster than other people. Feelings about removing negativity from your life the fast and hard way.
Example: A man dreamed of having severe diarrhea that got all over his clothes and wouldn't flush. In waking life he had spent a lot of money on a new house and was having problems balancing his finances due to all the unexpected expenses. The diarrhea may have reflected the sense of urgency and embarrassment at having to reduce spending so quickly in order to stabilize his finances.