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Hematochezia vs. Melena: Differentiating Types of Blood in Stools

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Blood in stools, whether visible or hidden, can be a concerning symptom that warrants immediate attention. It can indicate underlying medical conditions or gastrointestinal issues. Two common types of blood in stools are hematochezia and melena.

In this comprehensive guide, we will explore the differences between hematochezia and melena, their potential causes, and when to seek medical evaluation.

Understanding Blood in Stools

Blood in stools, also known as rectal bleeding, can manifest in various forms, including visible blood, black or tarry stools, or the presence of blood detectable only through laboratory tests. It’s essential to differentiate between the types of rectal bleeding to determine the underlying cause and appropriate treatment.


Hematochezia refers to the passage of bright red or maroon-colored blood in stools. It is typically fresh blood originating from the lower gastrointestinal tract, including the rectum and the colon. Hematochezia is often visible and can range from streaks of blood on the surface of stools to blood coating the stool or mixed within it.


Melena, on the other hand, refers to the passage of black, tarry, and foul-smelling stools. This type of rectal bleeding usually originates from higher up in the gastrointestinal tract, such as the stomach or the upper small intestine. The dark color and foul odor of melena result from the digestion of blood as it passes through the digestive system.

Causes of Hematochezia

Hematochezia is typically associated with bleeding in the lower gastrointestinal tract. Some common causes of hematochezia include:

  • Hemorrhoids. Hemorrhoids are swollen blood vessels in the rectum or anus and can cause bleeding during bowel movements.
  • Anal Fissures. These are small tears in the lining of the anus, often caused by passing hard stools. They can result in bright red blood in stools.
  • Diverticular Disease. Diverticula are small pouches that can develop in the colon. If they become inflamed or infected, they may bleed and cause hematochezia.
  • Inflammatory Bowel Disease (IBD). Conditions like Crohn’s disease and ulcerative colitis can lead to inflammation and ulcers in the intestines, which may cause bleeding.
  • Colorectal Polyps or Cancer. Precancerous polyps or colorectal cancer can cause bleeding in the lower gastrointestinal tract, leading to hematochezia.
  • Gastrointestinal Infections. Infections, such as those caused by bacteria or parasites, can result in hematochezia due to inflammation and damage to the intestinal lining.
  • Anal or Rectal Trauma. Any injury or trauma to the anal or rectal area can lead to hematochezia.
  • Medications. Certain medications, particularly nonsteroidal anti-inflammatory drugs (NSAIDs), can irritate the gastrointestinal lining and lead to bleeding.

Causes of Melena

Melena typically arises from bleeding in the upper gastrointestinal tract. Common causes of melena include:

  • Peptic Ulcers. Open sores that develop on the lining of the stomach or the upper part of the small intestine can cause bleeding, resulting in melena.
  • Esophageal Varices. Enlarged veins in the lower esophagus, often associated with liver disease, can rupture and cause significant upper gastrointestinal bleeding.
  • Upper Gastrointestinal Cancers. Cancers of the esophagus, stomach, or duodenum can cause bleeding and lead to melena.
  • Medications. Some medications, such as iron supplements or bismuth-containing compounds, can lead to dark stools resembling melena.
  • Gastrointestinal Vascular Malformations. Abnormal blood vessels in the upper gastrointestinal tract can rupture and cause melena.
  • Bleeding Disorders. Conditions that affect blood clotting, such as hemophilia or von Willebrand disease, can lead to melena.

Differentiating Hematochezia from Melena

Distinguishing between hematochezia and melena is critical for identifying the source of bleeding and guiding further evaluation. Several key characteristics help differentiate the two:

Color of Stools

  • Hematochezia. Stools appear bright red or maroon, indicating fresh blood.
  • Melena. Stools are black, tarry, and foul-smelling, indicating digested blood.

Location of Bleeding

  • Hematochezia. Typically originates from the lower gastrointestinal tract, including the colon and rectum.
  • Melena. Usually originates from the upper gastrointestinal tract, such as the stomach or upper small intestine.

Blood Consistency

  • Hematochezia. Blood is often more liquid and less viscous in the stool.
  • Melena. Blood is mixed with stool, making it tar-like and sticky.

Blood Characteristics

  • Hematochezia. Blood may be visibly present on the surface of stools, mixed with stools or seen when wiping.
  • Melena. Blood is mixed with stools. At times, it is only detectable through laboratory tests.


  • Hematochezia. Stools typically do not have a foul odor related to the presence of fresh blood.
  • Melena. Stools have a distinct foul odor resulting from the digestion of blood.

When to Seek Medical Evaluation

Regardless of whether you experience hematochezia or melena, rectal bleeding should prompt medical evaluation. Consult a healthcare provider or seek emergency care if:

You Experience Unexplained Blood in Stools

If you notice blood in your stools or on the toilet paper and do not have a clear explanation, such as hemorrhoids, it is important to seek medical attention. Even with hemorrhoids, frequent and large amounts of blood warrant medical attention.

You Have Additional Symptoms

Accompanying symptoms such as abdominal pain, changes in bowel habits, unexplained weight loss, or fatigue should be discussed with a healthcare provider.

The Bleeding is Severe

Heavy or persistent rectal bleeding is a medical emergency and requires immediate evaluation.

You Are at Increased Risk

If you have a personal or family history of gastrointestinal conditions, bleeding disorders, liver disorders or risk factors for gastrointestinal cancers, you should undergo regular screening and consult a healthcare provider regarding any rectal bleeding.

In all cases, it’s essential to communicate openly with your healthcare provider about the presence of blood in stools, the characteristics of the bleeding, and any associated symptoms. This information will help determine the source of the bleeding and guide appropriate diagnostic tests and treatment.


Blood in stools can be a concerning symptom with various potential causes, including hematochezia and melena. Understanding the differences between these types of rectal bleeding is crucial for identifying the source and guiding appropriate medical evaluation and treatment.

Regardless of the type of rectal bleeding you experience, seeking medical attention is essential. Your healthcare provider can conduct a comprehensive evaluation to determine the underlying cause and provide appropriate care and management.

Early diagnosis and timely treatment can significantly improve outcomes for individuals with rectal bleeding, whether it is due to a minor condition or a more serious underlying issue. Open communication with your healthcare provider and adherence to recommended diagnostic and treatment protocols are key to maintaining your health and well-being.

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