Feces or stool are the indigestible by-products of digestion that are stored in the rectum until expelled through the anus. It consists primarily of cellulose and other similar materials which the body has no digestive enzymes to process, together with large quantities of bacteria, primarily Escherichia coli.
Feces are often tested for pathogens or other indication of disease to determine the health of the patient. They should contain no digested blood, parasites or unusual bacteria. The consistency of feces is also an important diagnostic indicator. Healthy feces should be soft, easy to pass, and should come out in large pieces. Feces that are too hard and come out in pellet form often indicate constipation. Feces that come out completely as a liquid are typical of diarrhea.