View source for Melena

{{Short description|Medical condition with dark feces}}
{{For|similar terms|Malena (disambiguation)|Malina (disambiguation)|Meleana (disambiguation)|Melina (disambiguation)|Milena (disambiguation)|Molina (disambiguation)}}
{{More footnotes|date=December 2011}}
{{Infobox medical condition
| name = Melena
| synonyms = Melaena, melæna
| pronunciation = [[wikt:melena#Pronunciation|/məˈliːnə/ or /ˈmɛlɪnə/]]
| image = Melena Bleeding DU.jpg
| caption = 
| field = [[General surgery]], [[gastroenterology]]
| symptoms = Dark blood in stool
| complications = 
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| causes = {{hlist|[[Gastritis]]|[[Gastrointestinal bleeding]]|[[Stomach cancer]]}}
| risks = 
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}}

'''Melena''' is a form of [[blood in stool]] which refers to the dark black, tarry [[feces]] that are commonly associated with [[upper gastrointestinal bleeding]].<ref>{{MedlinePlusEncyclopedia|003130|Bloody or tarry stools}}, retrieved 19 July 2010.</ref> The black color and characteristic strong odor are caused by [[hemoglobin]] in the blood being altered by [[digestive enzyme]]s and [[intestinal bacteria]].<ref name="davidsons">{{cite book |editor-last1=Walker |editor-first1=Brian |editor-last2=Colledge |editor-first2=Nicki |editor-last3=Ralston |editor-first3=Stuart |editor-last4=Penman |editor-first4=Ian |year=2014 |title=Davidson's Principles and Practice of Medicine |location=Edinburgh |publisher=Churchill Livingstone |page=854 |isbn=978-0-7020-5103-6 |edition=22nd  }}</ref>

[[Iron supplements]] may cause a grayish-black stool that should be distinguished from melena,<ref>{{cite book|last=Navarra|first=Tova |title=The Encyclopædia of Vitamins, Minerals, and Supplements |url=https://books.google.com/books?id=upI55jwytpQC&q=iron+tablets+black+stool&pg=PA100|year=2004|publisher=[[Infobase Publishing]]|isbn=9781438121031 |quote=Iron supplements cause a grayish-black stool that should be distinguished from the black, tarlike stool that occurs from bleeding ulcer.}}</ref> as should black coloration caused by a number of medications, such as [[bismuth subsalicylate]] (the active ingredient in [[Pepto-Bismol]]), or by foods such as [[beetroot]], black [[liquorice]], or blueberries.<ref>{{cite web | url = https://medlineplus.gov/ency/article/003130.htm | title =Bloody or tarry stools | access-date = 2009-11-30 | date = 2009-11-01 | last = Dugdale | first = David | publisher = [[National Institutes of Health]] }}</ref>

==Causes==
The most common cause of melena is [[peptic ulcer]] disease.<ref>{{cite book|last1=Walker|first1=HK|last2=Hall|first2=WD|last3=Hurst|first3=JW |title=Clinical Methods: The History, Physical, and Laboratory Examinations |chapter=Hematemesis, Melena, and Hematochezia|url=https://www.ncbi.nlm.nih.gov/books/NBK411/|year=1990|publisher=Butterworths|isbn=9780409900774|quote=Melena strongly suggests, and hematemesis confirms, that bleeding is of upper gastrointestinal origin…Peptic ulcer, the most common cause of gastrointestinal hemorrhage, should be pursued through questions about epigastric distress, the relationship of symptoms to food intake, and a history of peptic ulcer disease.}}</ref> However, any bleeding within the upper gastrointestinal tract or the ascending colon can lead to melena.<ref name="talley">{{cite book |last1=Talley |first1=Nicholas |author-link1=Nicholas Talley |last2=O'Connor |first2=Simon |year=2014 |title=Clinical Examination: A Systematic Guide To Physical Diagnosis |location=Chatswood |publisher=Churchill Livingstone |page=179 |isbn=9780729541473 |edition=7th  }}</ref> Melena may also be a complication of anticoagulant medications, such as [[warfarin]].<ref>{{cite journal |last1=Di Minno |first1=Alessandro |last2=Spadarella |first2=Gaia |last3=Spadarella |first3=Emanuela |last4=Tremoli |first4=Elena |last5=Di Minno |first5=Giovanni |year=2015 |title=Gastrointestinal bleeding in patients receiving oral anticoagulation: Current treatment and pharmacological perspectives |journal=Thrombosis Research |volume=136 |issue=6 |pages=1074–81 |doi=10.1016/j.thromres.2015.10.016 |pmid=26508464 }}</ref>

Causes of upper gastrointestinal bleeding that may result in melena include malignant tumors affecting the esophagus, stomach or small intestine, hemorrhagic blood diseases, such as [[thrombocytopenia]] and [[hemophilia]], [[gastritis]], [[stomach cancer]], [[esophageal varices]], [[Meckel's diverticulum]] and [[Mallory-Weiss syndrome]].<ref name="harrison41">{{cite book | editor1-first=Dan L|editor1-last=Longo|editor2-first=Anthony S|editor2-last=Fauci|editor3-first=Dennis L|editor3-last=Kasper|editor4-first=Stephen L|editor4-last=Hauser|editor5-first=J. Larry|editor5-last=Jameson|editor6-first=Joseph|editor6-last=Loscalzo| title=Harrison's principles of internal medicine | publisher=McGraw-Hill | location=New York | year=2012 | edition=18th|chapter=41. Gastrointestinal Bleeding|first=Loren|last=Laine|isbn=978-0-07-174889-6 |page=320}}</ref>

Causes of "false" melena include [[iron supplements]], [[Pepto-Bismol]], [[Maalox]], and [[lead]], blood swallowed as a result of a nose bleed ([[epistaxis]]), and blood ingested as part of the diet, as with consumption of [[black pudding]] (blood sausage), or with the traditional African [[Maasai people|Maasai]] diet, which includes much blood drained from cattle.{{citation needed|date=February 2018}}

Melena is considered a [[medical emergency]] as it arises from a significant amount of bleeding. Urgent care is required to rule out serious causes and prevent potentially life-threatening emergencies.

A less serious, self-limiting case of melena can occur in newborns two to three days after delivery, due to swallowed maternal blood.{{citation needed|date=February 2018}}

==Diagnosis==
In acute cases, with a large amount of blood loss, patients may present with [[anemia]] or low blood pressure. However, aside from the melena itself, many patients may present with few symptoms.  Often, the first approach is to use endoscopy to look for obvious signs of a bleed. In cases where the source of the bleed is unclear, but melena is present, an upper endoscopy is recommended, to try to ascertain the source of the bleed.{{citation needed|date=February 2018}}

Lower gastrointestinal bleeding sources usually present with hematochezia or frank blood.  A test with poor sensitivity/specificity that may detect the source of bleeding is the tagged red blood cell scan. This is especially used for slow bleeding (<0.5 ml/min). However, for rapid bleeding (>0.5 ml/min), mesenteric [[Angiography|angiogram]] ± embolization is the gold standard. [[Colonoscopy]] is often first line, however.{{citation needed|date=February 2018}}

===Melena versus hematochezia===
Bleeds that originate from the lower gastrointestinal tract (such as the [[sigmoid colon]] and [[rectum]]) are generally associated with the passage of bright red blood, or [[hematochezia]], particularly when brisk. Only blood that originates from a more proximal source (such as the [[small intestine]]), or bleeding from a lower source that occurs slowly enough to allow for enzymatic breakdown, is associated with melena.  For this reason, melena is often associated with [[blood]] in the [[stomach]] or [[duodenum]] ([[upper gastrointestinal bleeding]]), 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.<ref name="harrison41"/>{{rp|322}}  One often-stated rule of thumb is that melena only occurs if the source of bleeding is above the [[suspensory muscle of the duodenum|ligament of Treitz]] although, as noted below, exceptions occur with enough frequency to render it unreliable.{{citation needed|date=February 2018}}

==Etymology==
The origin of ''melena'' is dated to the early 19th century via [[Neo-Latin|modern Latin]], via Greek ''melaina'' (feminine of ''melas'', black).{{citation needed|date=February 2018}}

==See also==
* [[Blood in stool]]
* [[Dieulafoy's lesion]]
* [[Hematemesis]]

==References==
{{reflist}}

== External links ==
{{Medical resources
|  ICD10       = {{ICD10|K|92|1|k|90}}
|  ICD9        = {{ICD9|578.1}}
|  MedlinePlus = 003130
}}
{{Gastroenterology}}
{{Authority control}}

[[Category:Bleeding]]
[[Category:Digestive disease symptoms]]
[[Category:Feces]]