Negative Fecal Occult Blood Tests: Causes and Next Steps

Hemorrhage in stool with negative fecal occult blood test?

Recently, I had a fecal occult blood test that showed visible blood, but the results came back negative.
1.
Could this be due to hemorrhoids or anal fissures, and how can it be negative if there is visible blood? I have also been experiencing frequent left abdominal pain, about 5 cm from the navel (it hurts more when fasting, but feels better after eating), and I have a history of recurrent gastroenteritis.
I have undergone both colonoscopy and gastroscopy, which only showed mild ulcers.
2.
Is there a need to perform a small bowel endoscopy? Is it common for polyps or tumors to develop in the small intestine? 3.
Can a small bowel endoscopy visualize the entire segment?

Kai, 30~39 year old female. Ask Date: 2024/03/26

Dr. Hu Guozheng reply Gastroenterology and Hepatology

It is recommended to discuss further treatment or examinations with your attending physician.
Thank you.

Reply Date: 2024/03/26

More Info

Understanding negative fecal occult blood tests (FOBT) can be quite perplexing, especially when there are visible signs of blood in the stool. Let's break down your concerns and provide clarity on the potential causes and next steps.

1. Visible Blood vs. Negative FOBT: It's important to understand that the FOBT is designed to detect hidden (occult) blood in the stool, which may not be visible to the naked eye. If you are seeing blood in your stool, it could be due to several reasons, including hemorrhoids or anal fissures, which are common causes of visible blood. These conditions can cause bleeding that may not be detected by the FOBT, especially if the blood is not mixed well with the stool or if the bleeding is intermittent. In contrast, the FOBT may yield a negative result if the blood is not present in sufficient quantities during the time of testing or if the test is not sensitive enough to detect it.

2. Abdominal Pain and Gastrointestinal Issues: The left abdominal pain you are experiencing, especially if it is relieved after eating, could be related to various gastrointestinal conditions. Given your history of recurrent gastroenteritis and the previous findings of mild ulcers, it is advisable to monitor this symptom closely. If the pain persists or worsens, further evaluation may be warranted.
3. Need for Small Bowel Endoscopy: Regarding your question about whether a small bowel endoscopy (enteroscopy) is necessary, it depends on your symptoms and the findings from previous examinations. Small bowel tumors or polyps are less common than those in the colon but can occur. If you have persistent symptoms that are unexplained by previous tests, a small bowel endoscopy may be a reasonable next step. This procedure can help visualize the small intestine and assess for any abnormalities, including polyps or tumors.

4. Extent of Small Bowel Endoscopy: Small bowel endoscopy can vary in its ability to visualize the entire small intestine. Traditional enteroscopy may allow for examination of a significant portion of the small bowel, but it may not reach the very end of the ileum. Newer techniques, such as capsule endoscopy, allow for a more comprehensive view of the small intestine, as the capsule can travel through the entire length of the bowel. However, it does not allow for biopsies or interventions.

In summary, while a negative FOBT in the presence of visible blood can be confusing, it is essential to consider other potential causes such as hemorrhoids or fissures. Given your symptoms and history, further evaluation, including a small bowel endoscopy, may be warranted to rule out any serious conditions. Always consult with your healthcare provider for personalized advice and to determine the best course of action based on your specific situation. Regular follow-ups and monitoring of your symptoms are crucial in managing your gastrointestinal health effectively.

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