What are the differences between common black stool and black stool caused by gastrointestinal bleeding?

Generally, common black stool and black stool caused by gastric bleeding can be differentiated according to stool appearance, accompanying symptoms, triggers, duration, and fecal occult blood test results. Specific differences include stool color and luster, physical reactions, inducing factors, duration, and occult blood test results. Detailed analysis is as follows:

1. Stool Color and Luster

Ordinary black stool is often caused by diet or medications. Its color is usually gray-black or dark black, with a dry texture and no obvious luster, resembling charcoal ash. In contrast, black stool from gastric bleeding contains iron sulfide formed after blood digestion in the intestines. Its color resembles tarry black, with a shiny, sticky surface similar to the texture of an asphalt road. When wiped, it leaves black sticky residue on toilet paper.

2. Accompanying Physical Symptoms

Ordinary black stool generally does not have specific accompanying symptoms. There is no discomfort after defecation, nor are there symptoms such as abdominal pain or fatigue. Black stool caused by gastric bleeding is often accompanied by upper abdominal dull pain, distension, or cramping pain. Symptoms such as dizziness, palpitations, and pale complexion may also appear. Severe cases may be accompanied by hematemesis (vomiting blood) or syncope (fainting). These reactions are related to mucosal damage and blood loss caused by gastric bleeding.

3. Triggering Factors

Ordinary black stool often has clear triggers, such as eating animal blood or liver, or taking iron supplements or bismuth preparations. Once the related food or medication is discontinued, the stool color gradually returns to normal. Gastric bleeding-related black stool is usually caused by gastric diseases, such as excessive alcohol consumption, peptic ulcer, or gastritis. It typically lacks specific dietary or drug triggers and often occurs after experiencing gastric discomfort.

4. Duration

Ordinary black stool lasts for a short duration. Once the triggering food or drug is discontinued, the stool color usually returns to normal within one or two days. The duration of gastric bleeding-related black stool is related to the amount of bleeding. If not treated promptly, melena (black stool) may persist and even worsen with increased bleeding. Only after treating the gastric bleeding does the stool color gradually return to normal.

5. Occult Blood Test Results

When performing a fecal occult blood test on ordinary black stool, if the cause is dietary, the test result may be positive, but it will turn negative after eliminating the related food. In contrast, the fecal occult blood test result for gastric bleeding-related black stool remains persistently positive and does not change with dietary adjustments. This is because gastric bleeding causes continuous blood residue in the intestinal tract.

In addition, if you are unable to distinguish the type of black stool on your own, it is recommended to seek medical attention promptly. Individuals with underlying gastric conditions such as peptic ulcer or gastritis should prioritize ruling out the possibility of gastric bleeding when black stool appears.