What is “fecal occult blood”?
“Fecal occult blood” refers to the presence of small quantities of blood in the stool that
cannot be seen with the naked eye (“occult” means “concealed from view”). The blood
can come from anywhere in the digestive tract, including the mouth, stomach, intestines
or rectum.
Why test for fecal occult blood?
Just like a leaky faucet will waste a large
amount of water over time, a small amount of
bleeding into the intestinal tract over a long
period of time can lead to substantial blood loss.
If left untreated this bleeding may lead to
anemia or "iron-poor blood". The fecal occult
blood test is a simple, non-invasive way to
determine if there is bleeding in the digestive
What causes fecal occult blood?
There are many causes for occult blood in the stool, but some of the more common
causes include dental disease, internal parasites, ulcers, foreign bodies, bowel
inflammation, and tumors.
What sample is required?
A small amount of fresh stool material is all that is needed. The veterinarian or
veterinary technician may collect stool material directly from
the pet's rectum using a gloved finger, or the pet owner
may be asked to provide a sample of fresh stool from the
pet. Ideally, the stool sample should be no more than 24
hours old.
How does the test work?
Blood contains a substance called hemoglobin. When a
stool sample containing blood is placed on a special testing
material, the chemical activity of hemoglobin causes a
visible color change in the testing material. This color
change signals the presence of blood.
Does the test always work?
The fecal occult test is a simple test, and may give false
negative or false positive results in certain situations.
The test may fail if blood is not distributed evenly throughout the stool sample, or if the
bleeding problem occurs intermittently rather than continuously. In both situations the
test result will be negative, even though there is bleeding in the digestive tract. The test
may also fail to detect bleeding in the digestive tract if the pet is receiving a Vitamin C
Diet can affect the accuracy of the fecal occult blood test. If a pet eats raw or
undercooked meat, raw vegetables, or even some types of canned food, the test for
fecal occult blood may be positive, even though the pet is not bleeding into the digestive
tract. To avoid this problem, the veterinarian may suggest feeding dry kibble exclusively
for 3 days prior to the test, and recommend that meat, meat scraps, and raw vegetables
not be fed to the pet during this interval.
Because of variability in the success of the fecal occult blood test, your veterinarian may
suggest repeating the test to ensure an accurate diagnosis.
 This client information sheet is based on material written by Kristiina Ruotsalo, DVM, DVSc, Dip ACVP &
Margo S. Tant BSc, DVM, DVSc.
© Copyright 2004 Lifelearn Inc. Used with permission under license. March 8, 2016