Occult Blood in Stool

The presence of blood in stool is often a cause for alarm, and rightly so, as it can be an indicator of various health conditions, some of which are quite serious. However, blood in stool is not always visible to the naked eye. This brings us to the concept of 'occult blood' in feces, a term used when traces of blood are so minute that they can only be detected through specific laboratory analyses. This post will delve into the significance of occult blood detection in stool, its implications, and the preparatory steps for the associated diagnostic test.

Understanding Occult Blood in Stool

The detection of occult blood in stool serves as a crucial screening test for colorectal cancer. It is suggested to undertake this test annually or biennially, starting from the age of 45 to 50. It's crucial to note that this screening method does not provide a diagnosis, but merely identifies individuals at risk for colorectal cancer and intestinal polyps.

If traces of blood are detected in the stool, it necessitates further diagnostic tests such as a colonoscopy. The presence of occult blood in stool can be attributed to a plethora of conditions, including but not limited to gastric ulcers, ulcerative colitis, Crohn's disease, diverticulitis, and hemorrhoids.

Despite its lack of diagnostic significance, the detection of occult blood in stool remains a valuable tool for early diagnosis, which subsequently leads to a significantly better prognosis. A study found that regular testing for occult blood in stool resulted in a 33% reduction in mortality when conducted annually, and a 21% reduction when performed biennially.

When to Test for Occult Blood in Stool

The test for fecal occult blood should be done even in the absence of symptoms, as colorectal tumors often remain asymptomatic for years. However, it's important to remember that a positive result does not necessarily indicate the presence of colon cancer. It's also possible for the pathological process to produce intermittent bleeding. Therefore, even if a recent test has yielded a negative result, it's advisable to consult a healthcare professional if you experience persistent changes in bowel habits, visible blood in stool, or a persistent feeling of rectal fullness after bowel movement.

Preparing for the Fecal Occult Blood Test

The preparation for the fecal occult blood test depends on the diagnostic techniques used by the laboratory. Traditional techniques are based on the use of guaiac and require the patient to avoid certain foods and medications to prevent false positives. This includes abstaining from consuming raw or semi-raw red meats, sources of vitamin C, alcohol, and anti-inflammatory medicines such as aspirin.

However, with the advent of latest generation tests, these dietary restrictions are no longer necessary. These tests use specific antibodies against the protein portion of human hemoglobin and are highly specific in screening tests for colorectal cancer.

To ensure accurate results, it's important to follow the collection instructions provided by the analysis center. These typically include using a sterile container with an internal spoon, avoiding mixing the stool with urine or toilet water, collecting the sample from three different points of the stool, and delivering the sample to the laboratory within a few hours.


The detection of occult blood in stool, while not diagnostic, is a valuable tool in the early detection of colorectal cancer and other gastrointestinal conditions. By understanding the significance of this test and how to prepare for it, individuals can take proactive steps towards their health. Regular testing and consultation with healthcare professionals in the presence of symptoms can greatly improve prognosis and survival rates.

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The Wellyme Team

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