Melena

A common sign of upper GI bleeding, melena is the passage of black, tarry stools containing digested blood. Characteristic color results from bacterial degradation and hydrochloric acid acting on the blood as it travels through the GI tract. At least 60 ml of blood is needed to produce this sign. (See Comparing melena to hematochezia.)  

Severe melena can signal acute bleeding and life-threatening hypovolemic shock. Usually, melena indicates bleeding from the esophagus, stomach, or duodenum, although it can also indicate bleeding from the jejunum, ileum, or ascending colon. This sign can also result from swallowing blood, as in epistaxis; from taking certain drugs; or from ingesting alcohol. Because false melena may be caused by ingestion of lead, iron, bismuth, or licorice (which produces black stools without the presence of blood), all black stools should be tested for occult blood.

Emergency Interventions

If the patient is experiencing severe melena, quickly take orthostatic vital signs to detect hypovolemic shock. A decline of 10 mm Hg or more in systolic pressure or an increase of 10 beats/minute or more in pulse rate indicates volume depletion. Quickly examine patient for other signs of shock, such as tachycardia, tachypnea, and cool, clammy skin. Insert a large-bore I.V. line to administer replacement fluids and allow blood transfusion. Obtain hematocrit, prothrombin time, international normalized ratio, and partial thromboplastin time. Place the patient flat with his head turned to the side and his feet elevated. Administer supplemental oxygen as needed.

History and physical examination

If the patient’s condition permits, ask when he discovered his stools were black and tarry. Ask about the frequency and quantity of bowel movements. Has he had melena before? Ask about other signs and symptoms, notably hematemesis or hematochezia, and about use of anti-inflammatories, alcohol, or other GI irritants. Also, find out if he has a history of GI lesions. Ask if the patient takes iron supplements, which may also cause black stools. Obtain a drug history, noting the use of warfarin or other anticoagulants.

Next, inspect the patient’s mouth and nasopharynx for evidence of bleeding. Perform an abdominal examination that includes auscultation, palpation, and percussion.

Medical causes

Colon cancer

On the right side of the colon, early tumor growth may cause melena accompanied by abdominal aching, pressure, or cramps. As the disease progresses, the patient develops weakness, fatigue, and anemia. Eventually, he also experiences diarrhea or obstipation, anorexia, weight loss, vomiting, and other signs and symptoms of intestinal obstruction.

With a tumor on the left side, melena is a rare sign until late in the disease. Early tumor growth commonly causes rectal bleeding with intermittent abdominal fullness or cramping and rectal pressure. As the disease progresses, the patient may develop obstipation, diarrhea, or pencil-shaped stools. At this stage, bleeding from the colon is signaled by melena or bloody stools.

Ebola virus

Melena, hematemesis, and bleeding from the nose, gums, and vagina may occur later with this disorder. Patients usually report abrupt onset of headache, malaise, myalgia, high fever, diarrhea, abdominal pain, dehydration, and lethargy on the fifth day of illness. Pleuritic chest pain, dry hacking cough, and pharyngitis have also been noted. A maculopapular rash develops between days 5 and 7 of the illness.

Esophageal cancer

Melena is a late sign of this malignant neoplastic disease that’s three times more common in men than women. Increasing obstruction first produces painless dysphagia, then rapid weight loss. The patient may experience steady chest pain with substernal fullness, nausea, vomiting, and hematemesis. Other findings include hoarseness, persistent cough (possibly hemoptysis), hiccups, sore throat, and halitosis. In the later stages, signs and symptoms include painful dysphagia, anorexia, and regurgitation.

Esophageal varices (ruptured)

This life-threatening disorder can produce melena, hematochezia, and hematemesis. Melena is preceded by signs of shock, such as tachycardia, tachypnea, hypotension, and cool, clammy skin. Agitation or confusion signals developing hepatic encephalopathy.

Gastric cancer

Melena and altered bowel habits may occur late with this uncommon cancer. More common findings include insidious onset of upper abdominal or retrosternal discomfort and chronic dyspepsia, which are unrelieved by antacids and exacerbated by food. Anorexia and slight nausea often occur, along with hematemesis, pallor, fatigue, weight loss, and a feeling of abdominal fullness.

Gastritis

Melena and hematemesis are common. The patient may also experience mild epigastric or abdominal discomfort that’s exacerbated by eating; belching; nausea; vomiting; and malaise.

Malaria

Melena may accompany persistent high fever and orthostatic hypotension in severe malaria. Other features include hemoptysis, vomiting, abdominal pain, diarrhea, oliguria, and headache, seizures, delirium, or coma. These findings are interspersed throughout the malarial paroxysm—chills, then high fever, and then profuse diaphoresis.

Mallory-Weiss syndrome

This condition is characterized by massive bleeding from the upper GI tract due to a tear in the mucous membrane of the esophagus or the junction of the esophagus and the stomach. Melena and hematemesis follow vomiting. Severe upper abdominal bleeding leads to signs and symptoms of shock, such as tachycardia, tachypnea, hypotension, and cool, clammy skin. The patient may also report epigastric or back pain.

Mesenteric vascular occlusion

This life-threatening disorder produces slight melena with 2 to 3 days of persistent, mild abdominal pain. Later, abdominal pain becomes severe and may be accompanied by tenderness, distention, guarding, and rigidity. The patient may also experience anorexia, vomiting, fever, and profound shock.

Peptic ulcer

Melena may signal life-threatening hemorrhage from vascular penetration. The patient may also develop decreased appetite, nausea, vomiting, hematemesis, hematochezia, and left epigastric pain that’s gnawing, burning, or sharp and may be described as heartburn or indigestion. With hypovolemic shock come tachycardia, tachypnea, hypotension, dizziness, syncope, and cool, clammy skin.

Small-bowel tumors

These tumors may bleed and produce melena. Other signs and symptoms include abdominal pain, distention, and increasing frequency and pitch of bowel sounds.

Thrombocytopenia

Melena or hematochezia may accompany other manifestations of bleeding tendency: hematemesis, epistaxis, petechiae, ecchymoses, hematuria, vaginal bleeding, and characteristic blood-filled oral bullae. Typically, the patient displays malaise, fatigue, weakness, and lethargy.

Typhoid fever

Melena or hematochezia occurs late in this disorder and may occur with hypotension and hypothermia. Other late findings include mental dullness or delirium, marked abdominal distention and diarrhea, marked weight loss, and profound fatigue.

Yellow fever

Melena, hematochezia, and hematemesis are ominous signs of hemorrhage, a classic feature, which occurs along with jaundice. Other findings include fever, headache, nausea, vomiting, epistaxis, albuminuria, petechiae and mucosal hemorrhage, and dizziness.

Other causes

Drugs and alcohol

Aspirin, other nonsteroidal anti-inflammatories, or alcohol can cause melena as a result of gastric irritation.

Special considerations

Monitor vital signs, and look closely for signs of hypovolemic shock. For general comfort, encourage bed rest, and keep the patient’s perianal area clean and dry to prevent skin irritation and breakdown. A nasogastric tube may be necessary to assist with drainage of gastric contents and decompression. Prepare him for diagnostic tests, including blood studies, gastroscopy or other endoscopic studies, barium swallow, and upper GI series. Prepare the patient for blood transfusions as indicated by his hematocrit.

Pediatric pointers

Neonates may experience melena neonatorum due to extravasation of blood into the alimentary canal. In older children, melena usually results from peptic ulcer, gastritis, or Meckel’s diverticulum.

Geriatric pointers

In elderly patients with recurrent intermittent GI bleeding without a clear etiology, angiography or exploratory laparotomy should be considered once the risk from continued anemia is deemed to outweigh the risk associated with the procedures.

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Book Source Details

• Book Title: Professional Guide to Signs & Symptoms (Fifth Edition)
• Author(s): Springhouse
• Year of Publication: 2006
• Copyright Details: Professional Guide to Signs & Symptoms (Fifth Edition), Copyright © 2006 Lippincott Williams & Wilkins.

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Copyright Details: Professional Guide to Signs & Symptoms (Fifth Edition), Copyright © 2008 Williams & Wilkins.

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• Back to symptom: Bloody stool: Introduction (review 352 causes)
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More About This Book: Title: Professional Guide to Signs & Symptoms (Fifth Edition) Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2006 ISBN: 1-58255-510-9

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