 | This article includes a list ofgeneral references, butit lacks sufficient correspondinginline citations. Please help toimprove this article byintroducing more precise citations.(December 2011) (Learn how and when to remove this message) |
| Melena | |
|---|---|
| Other names | Melaena, melæna |
 | |
| Pronunciation | |
| Specialty | General surgery,gastroenterology |
| Symptoms | Dark blood in stool |
| Causes | |
Melena is a form ofblood in stool which refers to the dark black, tarryfeces that are commonly associated withupper gastrointestinal bleeding.[1] The black color and characteristic strong odor are caused byhemoglobin in the blood being altered bydigestive enzymes andintestinal bacteria.[2]
Iron supplements may cause a grayish-black stool that should be distinguished from melena,[3] as should black coloration caused by a number of medications, such asbismuth subsalicylate (the active ingredient inPepto-Bismol), or by foods such asbeetroot, blackliquorice, or blueberries.[4]
The most common cause of melena ispeptic ulcer disease.[5] However, any bleeding within the upper gastrointestinal tract or the ascending colon can lead to melena.[6] Melena may also be a complication of anticoagulant medications, such aswarfarin.[7]
Causes of upper gastrointestinal bleeding that may result in melena include malignant tumors affecting the esophagus, stomach or small intestine, hemorrhagic blood diseases, such asthrombocytopenia andhemophilia,gastritis,stomach cancer,esophageal varices,Meckel's diverticulum andMallory-Weiss syndrome.[8]
Causes of "false" melena includeiron supplements,Pepto-Bismol,Maalox, andlead, blood swallowed as a result of a nose bleed (epistaxis), and blood ingested as part of the diet, as with consumption ofblack pudding (blood sausage), or with the traditional AfricanMaasai diet, which includes much blood drained from cattle.[citation needed]
Melena is considered amedical 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]
In acute cases, with a large amount of blood loss, patients may present withanemia 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]
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), mesentericangiogram ± embolization is the gold standard.Colonoscopy is often first line, however.[citation needed]
Bleeds that originate from the lower gastrointestinal tract (such as thesigmoid colon andrectum) are generally associated with the passage of bright red blood, orhematochezia, particularly when brisk. Only blood that originates from a more proximal source (such as thesmall 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 withblood in thestomach orduodenum (upper gastrointestinal bleeding), for example by apeptic 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.[8]: 322 One often-stated rule of thumb is that melena only occurs if the source of bleeding is above theligament of Treitz although, as noted below, exceptions occur with enough frequency to render it unreliable.[citation needed]
The origin ofmelena is dated to the early 19th century viamodern Latin, via Greekmelaina (feminine ofmelas, black).[citation needed]
Iron supplements cause a grayish-black stool that should be distinguished from the black, tarlike stool that occurs from bleeding ulcer.
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.
Authority control databases: National |
|---|