g. Gross Blood. When blood is present in feces in gross amounts, the color of
the stool specimen may be red, gray, or black. Some common causes of large amounts
of blood in fecal specimens are nosebleeds, esophageal varices, ulcers, carcinoma of the
gastrointestinal tract, and hemorrhoids. When blood is present in trace (occult) amounts,
chemical tests are required for detection. Meat in an individual's diet may cause
reactions in some of the chemical tests. Thus, the patient should be placed on a meat-
free diet for two or three days before the test for reliable results.
h. Adult Parasites. Often helminths are observed in stool specimens. The most
common is the roundworm, Ascaris lumbricoides, which is quite large. Some of the
others such as the hookworm, Trichuris trichiura, and tapeworms are usually found only
after comminution, straining, and searching the debris with a hand lens. Enterobius
vermicularis adults are usually found on the surface of the specimen. There are
constituents normally found in fecal specimens that resemble helminths, but are artifacts.
Where sanitation is poor, fly larvae are frequently seen and mites are occasionally found
in submitted samples.
i. Pollen. Pollen grains may frequently be confused with eggs of parasites and
protozoan cysts. Varieties of pollen differ according to geographic location and quantities
will vary with seasonal changes. When observed in fecal specimens, these pollen grains
(artifacts) must be differentiated from the true parasitic objects.
2-17. OCCULT BLOOD IN FECES
Trace amounts of blood may be present in feces from gastrointestinal lesions or
from the consumption of products containing blood. Testing for occult blood in suspected
or unsuspected cases with internal bleeding assists in the diagnosis. Ideally, this test
should be performed when the patient's diet is controlled since consumption of rare meat
and other food may be the cause of positive reactions.
a. Hemacult Tablets.
STEP 1: Smear a solid specimen of feces on filter paper, covering an area about the
size of a nickel. Do not use an emulsion.
STEP 2: Place a blood detection tablet in the center of the smeared specimen.
STEP 3: Place one drop of distilled water on the tablet, wait five or 10 seconds, and
place a second drop on the tablet so that it runs down the sides onto the filter
STEP 4: Note the color change and then record results.