Melena: Black, Tarry Stools

What melena looks like

Melena is distinctive once you know it:

• Color: jet black, not just dark brown or dark green
• Texture: sticky, shiny and tar-like, often hard to flush and smearing on the paper
• Smell: strong and unusually foul, from blood broken down by gut bacteria
• Consistency: often loose

Bleeding needs time in the gut to turn black. Usually 50 to 100 ml of blood or more has to enter the upper gut, and it takes several hours of transit. Melena can continue for a few days after the bleeding has stopped while old blood clears.

What melena indicates

Melena almost always means bleeding above the ligament of Treitz, the point where the duodenum joins the jejunum. This is called upper gastrointestinal bleeding. Less often, slow bleeding from the small intestine or right side of the colon causes melena when stool moves slowly.

Causes of melena

Peptic ulcers

Ulcers in the stomach or duodenum cause about half of upper GI bleeds. The two main causes of peptic ulcers are Helicobacter pylori infection and NSAIDs such as ibuprofen, naproxen and aspirin. Many bleeding ulcers cause no pain beforehand, especially in older people taking NSAIDs.

Gastritis and erosions

Inflammation and shallow erosions of the stomach lining from NSAIDs, alcohol or severe illness can bleed. NSAID gastropathy is common in people taking anti-inflammatories regularly.

Esophageal varices

Esophageal varices are swollen veins in the lower esophagus, caused by high pressure in the liver's blood supply from cirrhosis. They can bleed suddenly and heavily, often with vomiting of blood. This is a life-threatening emergency.

Other causes

• Esophagitis: severe acid reflux inflaming the esophagus
• Mallory-Weiss tear: a tear at the junction of the esophagus and stomach after forceful vomiting or retching
• Stomach or esophageal cancer: often slow bleeding with weight loss and anemia
• Abnormal blood vessels (angiodysplasia), most common in older adults
• Swallowed blood from a nosebleed or after dental surgery, which can also turn stool black
• Small bowel sources such as Crohn's disease, tumors or a Meckel's diverticulum

Things that raise the risk

• Taking NSAIDs or aspirin, especially with blood thinners, SSRIs or steroids
• Being over 60
• Previous ulcers or GI bleeding
• Heavy alcohol use
• Liver disease

Things that turn stool black without bleeding

• Iron tablets: dark green-black stools, usually formed and not tarry
• Bismuth subsalicylate (Pepto-Bismol): gray-black stool and a black tongue
• Foods: black licorice, blueberries, black pudding, dark chocolate cookies, beets in large amounts
• Activated charcoal

If you take iron and your stool suddenly becomes sticky, tar-like and foul, or you feel unwell, treat it as possible melena.

Symptoms that may come with melena

• Signs of blood loss: dizziness, especially on standing, fainting, a fast heartbeat, breathlessness, pale skin, cold sweat
• Vomiting blood or coffee-ground vomit, which confirms an upper GI source
• Upper belly pain or burning, suggesting an ulcer or gastritis
• Tiredness and breathlessness from anemia if the bleeding is slow
• Weight loss, poor appetite or trouble swallowing, which raise concern for cancer

How doctors assess melena

1. Rapid assessment of pulse, blood pressure and signs of shock.
2. Rectal exam to look at the stool.
3. Blood tests: hemoglobin, blood urea (often raised in upper GI bleeding), clotting, liver tests and blood type.
4. Risk scoring such as the Glasgow-Blatchford score, which helps decide who needs admission and who can be investigated as an outpatient.
5. Upper endoscopy (EGD): a camera passed through the mouth into the stomach and duodenum, usually within 24 hours. It finds the source and treats it at the same time.
6. Further tests if endoscopy is normal: colonoscopy, capsule endoscopy of the small intestine, or CT angiography.

Treatment

• Resuscitation: IV fluids and blood transfusion if needed.
• Endoscopic treatment: clips, heat, injection of adrenaline, or bands for varices.
• Acid-suppressing medicine: high-dose proton pump inhibitors for ulcers.
• Treating the cause: antibiotics to clear H. pylori, stopping NSAIDs, reviewing blood thinners with your doctor (do not stop prescribed blood thinners by yourself).
• For varices: medicines to lower portal pressure, antibiotics, and sometimes a shunt procedure (TIPS).
• Interventional radiology or surgery if bleeding cannot be controlled endoscopically.

Frequently asked questions

Is melena black tarry stool?

Yes. Melena is the medical name for black, sticky, tar-like stool that smells unusually bad. The color and texture come from blood that has been digested on its way through the gut. Dark stool that is formed and normal-smelling is usually not melena.

What does melena indicate?

Melena indicates bleeding in the upper digestive tract, most often from a stomach or duodenal ulcer, gastritis or esophageal varices. Less often the source is the small intestine or right colon. It always needs medical evaluation.

Is melena an emergency?

It should be treated as urgent. Get seen the same day for a single episode without symptoms. Call 911 or your local emergency number if you also feel dizzy or faint, have a fast heart rate, vomit blood, or have repeated black stools.

Can iron tablets cause melena?

Iron tablets make stool dark green or black, but this is not true melena. Iron stools are usually formed, not sticky or tarry, and do not smell unusually bad. A stool test for blood can tell the difference.

How long does melena last after bleeding stops?

Black stools can continue for 1 to 3 days after bleeding stops, while digested blood passes through. If black stools continue longer, or new red or black blood appears, bleeding may have restarted.