Black Stool: Causes, Risk Factors, Symptoms,Treatment & Prevention

Passage of black stool also known as melena is a symptom of upper gastrointestinal bleeding (i.e. bleeding from oesophagus , stomach, duodenum etc.) In some cases, melena is caused by the lower gastrointestinal bleeding where the blood is stored for the longer period of times as such in constipation. Some medications such as Iron tablets and bismuth compounds may also cause the passage of black stool. It is very important to distinguish the black stool caused by medication and upper gastrointestinal bleeding. Passage of black stool under medications such as iron tablet and bismuth compound is physiologically normal, is not foul smelling and does not stick to the pan of the toilet while black stool due to upper gastrointestinal bleed is foul smelling sticks to the pan and is accompanied by abdominal pain, nausea or vomiting of blood etc. 

A minimum amount of bleeding in the volume required to cause melena is about  50 ml. This blood is converted to black by the action of the gastric acid secretion, bacteria and air (oxidation). A small amount of blood is not visible by eye and goes unnoticed in many cases.

 Causes of black stool

  1. Consumption of iron tablets in pregnancy or to correct anemia.
  2. Gastrointestinal causes 
  3. Bleeding peptic ulcer disease
  4. Ruptured oesophageal varices 
  5. Mallory Weiss syndrome 
  6. Meckel’s diverticulum
  7. Gastric and duodenal cancer
  8. It may also be a sign of a drug overdose of anticoagulants like Warfarin 
  9. Bleeding disorders like hemophilia may also present with the black stool due to internal bleeding.

Black stool is described as the symptom of the upper gastrointestinal bleed in this article as these are pathogenic and in many cases life-threatening.

Bleeding Peptic ulcer disease is the most common cause of melena. These are the ulcers present in the stomach and the first part of the duodenum. 

Risk factors for peptic ulcer disease

  • Infection by Helicobacter pylori
  • Smoking
  • Alcohol consumption
  • use of a non-steroidal anti-inflammatory drug
  • Stress: psychological, burns, cerebrovascular disease 
  • Reduced blood flow in mucus due to ischemia  or shock 
  • Overproduction of the gastric acid: Zollinger Ellison syndrome 

15 to 20 % of people suffering from the peptic ulcer disease have upper gastrointestinal bleeding.The ulcers when bleeds in an amount more than 50 ml starts to produce a black stool.

Clinical features of black stool

Black stool due to iron supplementation often remains asymptomatic or may be present with constipation.

Passage of black stool due to upper gastrointestinal bleeding is a serious medical condition  and is often accompanied by 

  1. Recurrent abdominal pain accompanied by nausea or vomiting of blood.
  2. A light headache or dizziness. 
  3. Patient may look pale due to excessive  blood loss
  4. If an excess amount of blood is lost the patient may be unconscious and may present with the features of shock.
  5. Confusion or Coma depending on the amount of blood loss.

Signs found in patient  with upper gastrointestinal  bleeding

  1. Anemia: Anemia is a decrease hemoglobin concentration in blood, pale coloration of the skin, conjunctiva, smoothness of the tongue (absence of papilla) etc.
  2. Features of shock, such as tachycardia (increased heart rate), hypotension  (low blood pressure), tachypnea (increased respiratory rate ), sweating, cold peripheries occur when a large amount of blood is lost

 In young patients, the heart rate rises a little and is often accompanied by normal blood pressure despite a huge amount of blood loss. Hence it is very tough to access the amount of blood loss in the young patient.

  1. Signs of liver disease such as spider nevi, jaundice, ascites, splenomegaly etc.
  2. Presence of comorbid factors such as congestive cardiac failure , Renal failure , liver failure.
  3. Digital rectal examination reveals blood stained stool or black colored stool.

Diagnosis of black stool

Diagnosis is often made by the history, clinical features presented, but the patient and is confirmed by the investigations.

  1. Symptoms of patients, such as a passage of black stool and vomiting of blood.
  2. Pain over the epigastric region of the abdomen.
  3. History of peptic ulcer disease.
  4. Use of drugs such as  Nonsteroidal anti-inflammatory drugs has a history.
  5. History of smoking and alcohol intake for long periods of time.
  6. Comorbid factors such as liver disease 

The presence of these factors in history distinguishes the upper gastrointestinal bleeding from the lower gastrointestinal bleeding.

Investigations of black stool 

 It includes 

  1. Complete blood count: since hemoglobin level decreases in any case of bleeding. This test is done to detect the hemoglobin level, which in turn gives an idea about the amount of blood loss.
  2. Urea creatinine and electrolytes

 These are often used to see the kidney status. Prompt correction of electrolytes is life-saving.

Urea and creatinine levels show the extent of kidney damage due to volume loss.

  1. Liver function tests
     Liver diseases are an important factor leading to the upper gastrointestinal bleeding.To see the perfect picture of the liver functions liver function tests are very important. If liver functions are normal, then other factors of GI bleed should be considered. 
  2. Prothrombin time
    Patient with liver disease, chronic alcoholics, and patient under anticoagulant medications have altered prothrombin time.
  3. Bleeding time and clotting time
    To rule out the bleeding disorders such as hemophilia,  as a cause of black stool.
  4. Upper gastrointestinal  endoscopy
  5. Use of camera to visualize the bleeding point.
  6. It can also be used to ligate the bleeding point.
  7. Blood grouping and cross matching 
    To stabilize the haemodynamic system blood transfusion should be done. So blood grouping and crossmatching are very important.

Treatment  of upper gastrointestinal  bleeding or black stool 

 Upper gastrointestinal bleeding is an emergency medical condition which may lead to the death of an individual if not treated on time. As soon as the patient reaches the emergency department the following should be done.

  1. Secure airway, breathing, and circulation
    Airway compromise is one of the major risks of causing death going around with people suffering from upper gastrointestinal bleeding. If Airway is compromised basic airway maneuver should be used to correct it and be prepared for advancement airway.
    Oxygen supplementation should be used if the airway and breathing are normal   Fluid resuscitation should be done as soon as the intravenous access is secured. Transfusion with colloidal fluid helps in preventing the hypoglycemic shock.
    Blood transfusion should be done as early as possible. Blood transfusion cannot be delayed if the haemoglobin level is less than 10mg/dl or the patient is actively bleeding, or if the features  OS hypovolaemic shock is present.
  2. Urgent endoscopy:
    it should be done in the patients presenting with shock or known liver disease or if the patient is actively bleeding. An endoscopic arrest of bleeding can be achieved by using a heater probe or injection of diluted adrenaline in the bleeding point or ligation of bleeding by using the metallic clip.
  3. Regular monitoring of blood pressure, pulse, respiratory rate and the urine output.
  4. Repeat endoscopy if the bleeding continues or the signs of shock are still present 
  5. Surgery may be needed if the endoscopic arrest of bleeding fails. If rebleeding occurs only once in an old age or frail patient surgery should be done and if rebleeding occurs twice in young patients then surgical treatment should be implemented.
  • Treatment of underlying causes
  • Giving antibiotics and the anti ulcers can use as a treatment of peptic ulcer.
  • Treatment of liver disease.

Prevention of gastrointestinal  bleeds 

  1. Eradication of Helicobacter pylori
    The most important factor to prevent upper gastrointestinal bleeding is the eradication of the Helicobacter pylori infection. Eradication of Helicobacter pylori reduces the risk of peptic ulcer disease and subsequently bleeding from the ulcer.
  1. Avoiding smoking and alcohol consumption
    Avoiding smoking reduces the risk of peptic ulcer disease as well as the risk of the gastric and duodenal ulcers. Hence helps in prevention of upper gastrointestinal bleed.
    Alcohol abuse causes peptic ulcer disease and contributes to liver disease. Therefore avoiding alcohol reduces the risk factors for the gastrointestinal bleed.
  1. Treatment of critically ill patients with proton pump inhibitors like omeprazole and pantoprazole or with Histamine blockers like ranitidine helps in reducing the excessive secretion of the gastric acids and thus reduces the peptic ulcer disease and bleeding associated with it.
  1. Taking food in time, regular exercise and sleep help to reduce the stress related ulcers.

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