Macroscopic Examination (cont.)

The presence of blood in or on the specimen may be clinically relevant and should be reported. Dark-colored stools may indicate bleeding high in the gastrointestinal tract, and fresh (bright red) blood most often is the result of bleeding at a lower level. In certain parasitic infections (amebiasis with the true pathogen, Entamoeba histolytica), blood and mucus may be present. These areas of blood and mucus should be carefully examined for the presence of trophic amebae. Occult blood in the stool may or may not be related to a parasitic infection and could result from a number of different conditions. Ingestion of various compounds may give a distinctive color to the stool (iron, black; barium, light tan to white).

Many laboratories prefer that stool specimens from both in- and outpatients be submitted in some type of preservative. Rapid fixation of the specimen immediately after passage (by the patient) provides