The presence of blood in the feces may make them either black or bright red in color. This can occur because of infection, ulceration of the intestine or stomach, diverticular disease, malignant or nonmalignant tumors, abrasive foreign bodies, fissures, or hemorrhoids. Pale yellow or white feces suggest a disorder of bile production, usually an obstruction of the bile ducts. In children, greenish feces indicate that food has passed quickly through the digestive tract. Hard, nodular feces are associated with constipation, which may be a symptom of some other disorder.
Diarrhea produces excessively watery feces.
Feces that are flat and ribbon-like may be caused by an obstruction in the rectum. With jaundice, the feces may be pale and greasy. Worms and amebic dysentery are detected by inspecting the patient's feces. Chemical and microscopic analysis of a stool may show up abnormal amounts of fats, proteins, or sugars or small amounts of blood, which may indicate a disorder of digestion or malabsorption of food.