How to Distinguish Between Blood and Food Residue in Stool

Distinguishing whether it is hematochezia?

Hello, doctor.
I would like to ask how to distinguish if it is blood in my stool.
I read online that one way to differentiate is to see if the blood disperses in the water; if it doesn't, it's food residue, and if it does, it's blood.
I poked the red area in the toilet with a stick, and if it doesn't disperse, does that mean it's not blood? Or is the method of differentiation not like this?

Xiao Jia, 20~29 year old female. Ask Date: 2015/08/13

Dr. Lin Minghui reply Gastroenterology and Hepatology

Hello, if you are unable to distinguish, you can visit the Gastroenterology Department for a fecal occult blood test.
Sincerely, Dr.
Lin Ming-Hui, Attending Physician, Gastroenterology Department, Taoyuan General Hospital, Ministry of Health and Welfare.

Reply Date: 2015/08/13

More Info

Distinguishing between blood and food residue in stool can be a concerning issue, and it's important to approach this matter with caution and a clear understanding of the signs. While your inquiry about the method of determining whether the red substance in your stool is blood or food residue is valid, there are more reliable indicators to consider.

Firstly, the appearance of the stool can provide significant clues. Blood in the stool can appear in different forms depending on its source. For instance, bright red blood usually indicates bleeding from the lower gastrointestinal tract, such as the rectum or colon, while darker, tarry stools (melena) suggest bleeding from the upper gastrointestinal tract, such as the stomach or small intestine. In contrast, food residue may appear as undigested bits of food, which can vary in color and texture depending on what you have eaten.

The method you mentioned—observing whether the red substance disperses in water—can be misleading. While blood may not disperse as easily as food particles, this is not a definitive test. Instead, consider the following steps for a more accurate assessment:
1. Color and Consistency: Observe the color of the stool. Bright red blood is often a sign of fresh bleeding, while darker blood may indicate older blood. Food residue typically has a different texture and color based on your diet.

2. Presence of Other Symptoms: Pay attention to any accompanying symptoms. If you experience abdominal pain, cramping, diarrhea, or changes in bowel habits, these could indicate a gastrointestinal issue that requires medical attention.

3. Stool Characteristics: Note if the stool is formed or loose. Blood may alter the consistency of the stool, while food residue may not have the same effect.

4. Medical Evaluation: If you are uncertain or if you notice blood in your stool, it is crucial to seek medical advice. A healthcare professional can perform a thorough evaluation, including a physical examination and possibly diagnostic tests such as a stool test, colonoscopy, or imaging studies to determine the cause of the bleeding.

5. Avoid Self-Diagnosis: While it may be tempting to conduct home tests, self-diagnosis can lead to unnecessary anxiety or misinterpretation of symptoms. It is always best to consult with a healthcare provider for an accurate diagnosis and appropriate management.

In summary, while your method of testing for blood in stool by observing its behavior in water may provide some insight, it is not a reliable or comprehensive approach. The best course of action is to monitor your symptoms closely and consult a healthcare professional if you have any concerns about the presence of blood in your stool. Early evaluation and intervention can be crucial in addressing any underlying health issues effectively.

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