Black Stool: What Does It Mean?

What does a black stool indicate?

A black or dark red-colored stool is called tarry or bloody stools. However, passing dark-colored stools is not always caused by serious problems. One of the most common causes of black stools is the consumption of iron supplements, particularly in people who have had a colectomy or ostomy surgery. However, it would be another case if you have other symptoms such as persistently passing foul-smelling stool and if you have a history of gastrointestinal bleeding in the past.

A tarry or bloody stool may indicate injuries or bleeding in the gastrointestinal tract. Dark bowel movements may also occur as a result of eating dark-colored foods. Consult a doctor if you continue passing black or bloody stools to properly rule out other serious health conditions. 

Fast Facts About Black Stools

• In most cases, black stools are as a result of taking iron supplements or the consumption of black or dark-colored foods.
• A bleeding ulcer is the most common condition that causes black stools.
• A black-colored stool could indicate an upper GI tract problem.
• A stool test can be used to detect the presence of blood in the stool.
• Seek immediate medical help if you are passing black stools along with vomiting, diarrhea, or abdominal pain.
• If you suspect blood in your stool, speak with your healthcare provider right away. 

Symptoms

There are also other symptoms that may accompany black stools. However, the symptoms usually depend on the underlying medical condition. Some of the symptoms may include:

• Changes in bowel habits 
• Pain
• Fever
• Headache
• Fatigue or tiredness
• Sore throat
• Coughing

Some people may also experience other symptoms, which would include:

• Abdominal pain or cramps
• Indigestion
• Bloating
• Flatulence
• Foul-smelling stool
• Abdominal swelling
• Poor appetite
• Nausea and vomiting
• Diarrhea
• Unexplained weight loss
• Pain or burning sensation in the anal region

In certain cases, black stools may also indicate life-threatening medical conditions, which should be immediately evaluated by the doctor. Seek immediate medical help if you have any of the following symptoms along with passing black stools:

• A fever higher than 101 degrees Fahrenheit
• Altered alertness or mental status
• Sudden changes in behavior
• Weakness and fatigue
• Palpitations
• Tachycardia (rapid heart rate)
• Difficulty breathing and other respiratory issues
• Choking sensation
• Severe abdominal pain
• Severe diarrhea
• Hematemesis (vomiting of blood)

Causes

Bleeding in the Digestive System

When there is bleeding present in the upper region of the digestion system, then it can possibly lead to the occurrence of black or tarry stools. When this blood gets mixed with the digestive fluids present in the stomach, it would take the appearance of tarry or black stools. However, people who have a lower GI tract bleeding may pass stools with bloody streaks or clots instead of black or tarry stools. 

It usually takes a significant amount of bleeding (minimum of 100 milliliters) from the upper GI tract to cause black stools. The possible causes of an upper GI tract bleeding may include:

• Gastroesophageal laceration (a kind of tear at the junction of the stomach and the esophagus)
• Blood vessel malformation in the esophagus
• Stomach cancer
• Esophageal ulcer
• Bleeding peptic ulcers

Causes of lower GI tract bleeding:

• Hemorrhoids
• Colon polyps
• Anal fissures
• Intestinal infections
• Diverticular disease
• Crohn's disease
• Ulcerative colitis
• Ischemic colitis
• Blood vessel problems

Supplements, Medications, or Foods

Certain supplements, medications, and minerals may cause black stools. People who are taking iron supplements as a multivitamin for iron deficiency anemia and bismuth medicines like Pepto-Bismol may black stools. 

The consumption of dark-colored foods tends to give stools a darker appearance without the presence of blood. Some of those foods may include:

• Blueberries
• Blackberries
• Deep purple grapes
• Beets
• Purple grape juice
• Black licorice
• Dark chocolate
• Dark green leafy vegetables including spinach, greens, and kale (stools may appear dark green, which seem black-colored at a glance)

Abnormalities

In certain cases, black stools could also indicate circulatory abnormalities in the digestive system, such as vascular malformation of the GI tract, bowel ischemia, and esophageal varices. 

Diagnosis

Passing a black-colored stool alone is not enough when it comes to diagnosing blood in the stool. In most cases, doctors confirm the diagnosis through rectal examinations or fecal sample collection kits, which are then sent to the laboratory for further testing.

Several health conditions can cause blood in the stool. They include gastritis, bleeding ulcers, Mallory-Weiss tear (a tear in the esophagus due to severe vomiting), and esophageal varices. The tests used to determine the cause of GI bleeding include:

• Blood tests
• Stool culture
• Barium studies
• Esophagogastroduodenoscopy (EGD)
• Colonoscopy
• X-rays

Treatment

The treatment for bloody or tarry stools usually depends on its main cause. People who suffer from cancer and hemorrhoids can use stool softeners as recommended by their doctors. Taking a sitz bath can also help soothe pain due to hemorrhoids as well as prevent bleeding. Ulcers can be treated using acid-reducing medications. When it comes to infections and inflammatory bowel disease, antibiotics and immunosuppressant drugs are usually prescribed.

Surgery may be required in cases of vein abnormalities and blockages. Anemia may also develop if bleeding does not stop and a lot of blood is lost through the stool. In such cases, a blood transfusion may be needed to replenish the red blood cells.

If bloody stools are caused by polyps in the colon, it could indicate cancer or a precancerous condition. In some cases, polyp removal may be required. Other treatment options may include radiation therapy and chemotherapy in patients with cancer.

Complications

Passing black or tarry stools due to bleeding may result in the following conditions:

• Anemia
• Excess fatigue and weakness
• Hypovolemia
• Circulatory collapse due to hypovolemia

If you frequently pass black or dark-colored stools, make sure to consult a healthcare provider to properly diagnose and treat your condition to avoid these life-threatening complications.

Prevention

Avoiding the risk factors that can lead to an upper GI bleeding can prevent passing black stools. Risk factors include:

• Long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) – A full stomach is recommended when taking NSAIDs to prevent the irritation of the gastric mucosa.

• Smoking – This bad habit can irritate the gastric lining. Quitting smoking is highly recommended to prevent ulcers and gastritis.

• Excessive alcohol consumption – The stomach and the esophagus can get irritated when there is too much consumption of alcohol.

• Stress – Excessive hydrochloric acid in the stomach can be produced when people deal with too much stress.

• Skipping meals – The stomach continues to produce digestive juices even if you do not eat. Not eating for too long can cause acid reflux, stomach pain, and gastritis, which are the most common side effects of skipping meals.