Test Details: Stool samples should be evaluated macroscopically in terms of color, consistency, quantity, form and presence of mucus. The presence of a small amount of mucus in stool is normal. However, the presence of copious mucus or bloody mucus is abnormal. The normal color is tawny due to the presence of bilirubin and bile. In infants, the stool may be green, its consistency may be watery or pasty. Stool color varies greatly depending on diet. Clay-colored or putty colored stool is observed in biliary obstructions. If more than 100 mL blood is lost from the upper gastrointestinal system, black, tarry stool is observed. Besides bleeding, black-colored stool may also be observed due to iron or bismuth treatment. Red-colored stool is observed in lower gastrointestinal tract bleeding. Microscopic examination is a diagnostic tool for defining protozoa, helminths and fecal leukocytes. Erythrocytes and leukocytes are not observed in normal stool. In order to see leukocytes, examinations should be performed in stool samples obtained from the area with mucus. Leukocytes are generally observed in bacterial infections.