4yo complaining of belly ache and diarrhea for 2 days, no fever. any concern? she is usually very constipated.

Diarrhea: If she is drinking well and staying hydrated then observation is fine. It is possible that the diarrhea is what we call "spurious" diarrhea if her constipation has been severe enough. Spurious diarrhea is basically liquid stool leaking around a larger plug of stool. If that is the case then she will likely need some help getting rid of the plug. Follow up with her doctor tomorrow.

Make Dietary Changes: Dietary selection contributes to constipation: impairs the appetite; causes abd pain. New soft stool passes around hard stool; is mistaken for diarrhea. Inadequate dietary fluid/fiber commonly the cause. Prune juice helps; give 10-12 oz water, 19 gm fiber (fresh fruit/veggies, beans, whole grains) daily. Your child should see the doctor to check for medical causes if this has not already been done