Feces

Feces, also known as stool, is the solid or semisolid matter that remains after the digestion and absorption of food in the gastrointestinal tract. It is excreted through the anus during defecation and reflects the activity of the digestive system and the gut microbiota.

Composition and characteristics: Feces typically contain water (about 75%), bacteria (live and dead), undigested dietary fiber, shed intestinal cells, mucus, fats, inorganic matter, and bile pigments such as stercobilin, which contributes to the characteristic brown color. Bacterial activity and fermentation products contribute to odor and texture. Color and consistency can vary with diet, bile flow, and intestinal transit time.

Formation and excretion: After nutrients are absorbed in the small intestine, the remaining material moves into the colon where water is absorbed and the stool solidifies. The frequency and form of defecation are influenced by hydration, fiber intake, medications, illness, and gut motility. The Bristol Stool Chart is often used to describe stool form in a clinical context.

Health relevance: Stool analysis is used in medical diagnostics, including tests for occult blood and for detecting infections. The gut microbiome is studied through stool samples, and fecal microbiota transplantation uses donor stool to treat certain gut conditions under medical supervision.

Safety and handling: Feces can carry pathogens, so proper hygiene, sanitation, and disposal are important in clinical settings and at home to prevent spread of disease.