Green diarrhea is basically normal.Green colored stools/watery stools are usually seen with diarrhea.Bacteria in the colon break the bile(green color) salts down into simpler substances which are darker in color and hence imparts the normal color of stool.
Green stool often indicates that food has passed through the intestines faster than normal (called decreased bowel transit time), before it could be changed from green to brown.So during diarrhea,bowel transit time decreases and so imparts green color to the stool.So its normal to have green stool in diarrhea.Take appropriate measures to prevent dehydration.Drink plenty of water.
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