Melena overview: Difference between revisions

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Revision as of 19:29, 3 April 2013

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Melena or melaena refers to the black, "tarry" feces that are associated with gastrointestinal hemorrhage. The black color is caused by oxidation of the iron in hemoglobin during its passage through the ileum and colon.

Pathophysiology

Melena, is stool with blood, that has been altered by the gut flora, and appears black/"tarry".

Causes

The most common cause of melena is peptic ulcer disease. Any other cause of bleeding from the upper gastro-intestinal tract, or even the ascending colon, can also cause melena. Melena may also be a sign of drug overdose if a patient is taking anti-coagulants, such as warfarin. A less serious, self-limiting case of melena can occur in newborns two to three days after delivery, due to swallowed maternal blood.

References

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 ==Pathophysiology==
 [[Melena]], is stool with blood, that has been altered by the [[gut flora]], and appears black/"[[tar]]ry".
-===Melena vs. hematochezia===
-Bleeding originating from the lower GI tract (such as the [[sigmoid colon]] and [[rectum]]) is generally associated with the passage of bright red blood, or [[hematochezia]], particularly when brisk.  Blood acts as a [[cathartic]] agent in the intestine, promoting its prompt passage.  Only blood that originates from a high source (such as the [[small intestine]]), or bleeding from a lower source that occurs slowly enough to allow for oxidation, is associated with melena.  For this reason, melena is often associated with [[hemorrhage]] in the [[stomach]] or [[duodenum]] ([[upper gastrointestinal tract]]), for example by a [[peptic ulcer]]. A rough estimate is that it takes about 14 hours for blood to be broken down within the intestinal lumen; therefore if transit time is less than 14 hours the patient will have hematochezia and if greater than 14 hours the patient will exhibit melena. One often-stated rule of thumb is that melena only occurs if the source of bleeding is above the [[ligament of Treitz]].
 == Causes ==
-The upper part of the GI tract will usually cause black stools due to:
+The most common cause of melena is peptic ulcer disease. Any other cause of bleeding from the upper gastro-intestinal tract, or even the ascending colon, can also cause melena.  Melena may also be a sign of drug overdose if a patient is taking anti-coagulants, such as warfarin. A less serious, self-limiting case of melena can occur in newborns two to three days after delivery, due to swallowed maternal blood.
-* Abnormal [[blood vessel]]s (vascular [[malformation]])
-* A tear in the esophagus from violent vomiting ([[Mallory-Weiss tear]])
-* Bleeding stomach or [[duodenal ulcer]]
-* Inflammation of the stomach lining ([[gastritis]])
-* Lack of proper blood flow to the intestines ([[bowel]] [[ischemia]])
-* Trauma or foreign body
-* Widened, overgrown veins (called [[varices]]) in the esophagus and stomach
-==Diagnosis==
-===Symptoms===
-*[[Blood]] in [[stool]].
-*Black colored stool.
-===Physical Examinations===
-* Patients present with [[Anemia physical examination#Signs|signs]] of [[anemia]].
-*[[Vital signs]].
-** [[Pulse]].
-** [[Blood pressure]]
-** [[Respiratory rate]].
-** Core body [[temperature]].
-===Laboratory Findings===
-* Blood studies, including a complete blood count ( CBC) and differential, serum chemistries, clotting studies.
-* The presence of blood must be confirmed with either a positive hemoccult slide on rectal exam, frank blood on the examining finger, or a positive stool guaiac from the lab.
-===X Ray===
-* [[Chest X Ray]] should be ordered to rule out perforated viscus, [[aspiration pneumonia]].
-* [[Barium swallow|Barium studies]].
-* [[Abdominal x-ray|X Ray of the abdomen]].
-===CT===
-*Computed tomography scan is indicated for the evaluation
-**[[Liver]] disease.
-**Aortoenteric [[fistula]]
-===Other Imaging Findings===
-* Bleeding scan (nuclear medicine)
-* [[Colonoscopy]]
-* [[Esophagogastroduodenoscopy]]
-===Other Diagnostic Studies===
-* [[Stool culture]].
-* Tests for the presence of [[Helicobacter pylori]] [[infection]].
-* [[Nasogastric lavage]].
-===Medical Therapy===
-Following options should be considered:
-* [[Blood transfusion]]s
-* [[Intravenous fluids|IV Fluid]]s
-* Medications to decrease stomach acid.
-* Interventional radiography embolization.
-===Surgery===
-Surgery should be done if bleeding does not stop.
 == References ==