Gastrointestinal (GI) bleeding is usually categorized as either melena or hematochezia.
Melena refers to black stools, while hematochezia refers to fresh, red blood in your stool. This blood might be mixed in with your stool or come out separately. Hematochezia usually comes from the colon, while melena usually comes from a higher point in your GI tract.
Both melena and hematochezia are symptoms, not actual conditions. Many conditions can cause either type of bleeding. Some of these conditions are serious, so it’s important to follow up with your doctor immediately if you notice blood in your stool.
What are their symptoms?
Hematochezia is usually a bright red color. Remember, hematochezia is caused by bleeding in your colon, which is fairly close to your anus. The blood only travels a short distance, so it’s still fresh by the time it leaves your anus. You might notice it mixed in with your stool, though it can also come out separately.
In addition, hematochezia tends to cause more minor bleeding than melena does. Other symptoms that might accompany hematochezia include:
Melena causes black, tarry stools that are easy to distinguish from the brighter red associated with hematochezia. The blood is usually jet-black, similar to ink from a black ballpoint pen. Your stools might also look or feel sticky.
This blood is darker because it has to travel farther down your GI tract. By the time it reaches your anus, it’s been deoxygenated, which removes its bright red color. In addition to melena, you might also experience hematemesis, which refers to vomiting blood.
What causes them?
While both hematochezia and melena cause bloody stools, they each have different potential causes.
Hematochezia originates lower in your GI tract, usually in your colon.
Several things can cause bleeding in your lower GI tract, including:
- internal hemorrhoids
- diverticular disease, such as diverticulitis
- anal fissures
- colon cancer
- ischemic colitis
- inflammatory bowel disease (IBD)
- neoplastic polyps
- benign tumors
In children, hematochezia is usually caused by IBD, Meckel’s diverticulum, or juvenile polyps.
Melena is caused by bleeding higher up in your GI tract. This may be due to:
Some newborns have melena from swallowing blood during delivery.
How are they diagnosed?
Your doctor can usually differentiate between melena and hematochezia by simply looking at a stool sample. Based on the color of the blood, they’ll do additional testing to narrow down a diagnosis.
If you have hematochezia, your doctor will likely start with a colonoscopy. This involves inserting a small tube with a camera through your rectum. The device will give them a view of your lower GI tract, including your colon, so they can pinpoint where the blood is coming from. During the procedure, they may also take a small tissue sample for additional testing.
Other tests used to diagnose the cause of hematochezia include:
- Enteroscopy. You’ll swallow a small capsule containing a camera that produces images of your GI tract.
- Barium X-ray. Your doctor will have you swallow a contrast material called barium. They might also insert it into your rectum. This will help your GI tract show up on an X-ray.
- Radionuclide scanning. A small amount of radioactive material is injected into a vein while your doctor monitors your blood flow through a camera.
- Angiography. This involves injecting dye into a vein to make blood vessels visible on a CT scan or X-ray.
Laparotomy. This is a more invasive test that involves surgically opening your abdomen to find the source of bleeding.
Your doctor will use similar tests to diagnose the underlying cause of melena. They may also use:
- Esophagogastroduodenoscopy (EGD). A small tube with a camera and light attached to it is inserted through your mouth and down your esophagus. This will help your doctor check for signs of bleeding higher up in your GI tract.
- Blood, stool, or breath test. Your doctor may ask for a stool sample, take a blood sample, or schedule a breath test to check for signs of an infection, including those caused by Helicobacter pylori.
How are they treated?
Hematochezia and melena usually have different causes, but their treatments are very similar. Your doctor will start by focusing on stopping the bleeding.
Your doctor might use one or more of the following treatments, depending on the source of your bleeding:
- Endoscopic thermal probe. This involves burning the blood vessel or tissue that’s causing an ulcer.
- Endoscopic clips. These can close a bleeding blood vessel or other source of bleeding in the tissue in your GI tract.
- Endoscopic injection. Your doctor will inject a liquid near the source of bleeding that will stop the flow of blood.
- Angiographic embolization. This technique injects particles into the affected blood vessel.
- Endoscopic intravariceal cyanoacrylate injection. You’ll receive an injection near the affected area that contains a special glue to stop bleeding in enlarged veins in your stomach.
- Band ligation. This procedure involves placing small rubber bands around hemorrhoids or swollen veins (esophageal varices) to cut off their blood supply, which will make them dry up and fall off.
The bottom line
Hematochezia and melena both refer to having blood in your stool. While hematochezia causes bright red blood to appear in or around your stool, melena causes dark stools that often feel sticky. The difference in color is due to different bleeding sources. The dark blood associated with melena comes from your upper GI tract, while the red blood of hematochezia comes from your lower GI tract.
Regardless of your symptoms, it’s best to talk to your doctor if you notice any signs of blood in your stool.