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abnormally dark tarry feces containing blood (usually from gastrointestinal bleeding) (同)melaena

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/05/14 23:58:27」(JST)

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In medicine, melena or melæna refers to the black, "tarry" feces that are associated with upper gastrointestinal bleeding.^[1] The black color is caused by the hemoglobin in the blood being altered by digestive chemicals and intestinal bacteria.

Iron supplements may cause a grayish-black stool that should be distinguished from the black, tarlike stool that occurs from bleeding ulcer.^[2]

Melena vs. hematochezia

Bleeds that originate from the lower GI 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 high 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. One often-stated rule of thumb is that melena only occurs if the source of bleeding is above the ligament of Treitz although, as noted below, exceptions occur with enough frequency to render it unreliable.

Diagnosis

Patients sometimes present with anemia or low blood pressure. Very often, however, aside from the melena itself, there are no other symptoms. A digital rectal exam must be performed to assess for both presence and possible source of blood. Testing for blood in the stool with such tests as the stool guaiac are often performed, though it has only been validated for colorectal cancer screening. If this is to be performed, it should be done before the digital rectal exam to avoid trauma to the anal canal, and its ability to change management is debatable. If a source in the upper GI tract is suspected, an upper endoscopy can be performed to diagnose the cause.

Lower GI 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 angiogram ± embolization is the gold standard. Colonoscopy is often first line, however.

Causes

The most common cause of melena is peptic ulcer disease.^[3] Any other cause of bleeding from the upper gastrointestinal tract, or even the ascending colon, can also cause melena. Melena may also be a sign of drug overdose if a patient is taking anticoagulants, such as warfarin. It is also caused by tumors, especially malignant tumors affecting the esophagus, more commonly the stomach & less commonly the small intestine due to their bleeding surface. However,the most prominent and helpful sign in these cases of malignant tumors is haematemesis. It may also accompany hemorrhagic blood diseases (e.g. purpura & hemophilia). Other medical causes of melena include bleeding ulcers, gastritis, esophageal varices, Meckel's diverticulum and Mallory-Weiss syndrome.^{[citation needed]}

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 diet, which includes much blood drained from cattle.

Melena is often 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.

References

^ MedlinePlus Encyclopedia Bloody or tarry stools, retrieved 19 July 2010.
^ Navarra, Tova (2004). The Encyclopædia of Vitamins, Minerals, and Supplements. Infobase Publishing. Iron supplements cause a grayish-black stool that should be distinguished from the black, tarlike stool that occurs from bleeding ulcer.
^ Hurst, JW (1990). Clinical Methods: The History, Physical, and Laboratory Examinations. 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 past history of peptic ulcer disease..

UpToDate Contents

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1. 成人における急性上部消化管出血へのアプローチ approach to acute upper gastrointestinal bleeding in adults
2. 成人における上部消化管出血の主要な原因 major causes of upper gastrointestinal bleeding in adults
3. 小児における上部消化管出血に対するアプローチ approach to upper gastrointestinal bleeding in children
4. 成人における急性下部消化管出血に対するアプローチ approach to acute lower gastrointestinal bleeding in adults
5. 出血性消化性潰瘍の治療の概要 overview of the treatment of bleeding peptic ulcers

English Journal

Prospective randomized controlled trial to compare the effects of omeprazole and famotidine in preventing delayed bleeding and promoting ulcer healing after endoscopic submucosal dissection.

Tomita T, Kim Y, Yamasaki T, Okugawa T, Kondo T, Toyoshima F, Sakurai J, Tanaka J, Morita T, Oshima T, Fukui H, Hori K, Watari J, Matsumoto T, Miwa H.SourceDivision of Upper Gastroenterology, Department of Internal Medicine, Hyogo College of Medicine, Hyogo, Japan Division of Lower Gastroenterology, Department of Internal Medicine, Hyogo College of Medicine, Hyogo, Japan.
Journal of gastroenterology and hepatology.J Gastroenterol Hepatol.2012 Sep;27(9):1441-6. doi: 10.1111/j.1440-1746.2012.07144.x.
Background and Aims: Proton pump inhibitors (PPIs) are generally used to prevent delayed bleeding after endoscopic submucosal dissection (ESD) and to heal the artificial ulcers. However, it remains controversial whether PPIs or histamine-2 receptor antagonists (H(2) RAs) are more effective in pre
PMID 22497427

In Vivo Endoscopic Imaging of Ancylostomiasis-Induced Gastrointestinal Bleeding: Clinical and Biological Profiles.

Barakat M, Ibrahim N, Nasr A.SourceDepartment of Tropical Medicine and Gastroenterology, Assiut University Hospital, Assiut, Egypt; Department of Pediatrics, Assiut University Hospital, Assiut, Egypt.
The American journal of tropical medicine and hygiene.Am J Trop Med Hyg.2012 Aug 6. [Epub ahead of print]
Little data are available regarding the association of ancylostomiasis with overt gastrointestinal bleeding. This 6-year retrospective study describes the clinical and biological profiles of unexpectedly identified ancylostomiasis in a 4-month-old baby and four adults; they presented with melena and
PMID 22869629

Japanese Journal

Preparation of Enteric-coated Capsules of Beclomethasone Dipropionate for Patients with Intestinal Graft-versus-Host Disease and a Case Study

Murakawa Kiminaka,Sato Tomoaki,Maeda Yoshinobu,Kitamura Yoshihisa,Tanimoto Mitsune,Sendo Toshiaki
Acta Medica Okayama 67(5), 319-324, 2013-10-00
… Gut GVHD is accompanied by diarrhea, abdominal pain, and/or melena. …
NAID 120005341865

5年の経過で増大し出血を来したBrunner腺過形成の一切除例

白築祥吾,岡本健志,浜辺功一,仙譽学,西川潤,橋本憲輝,吉野茂文,坂井田功
山口医学 62(1), 43-48, 2013-02-01
… Melena was observed from 2 to 3 days before admission; …
NAID 120005246296

下血を契機に発見された潰瘍を伴う多発小腸憩室症の1例

横田恭之,橋本真一,柴田大明,播磨郷子,坂井田功
山口医学 62(1), 39-42, 2013-02-01
… び空腸に多発する潰瘍と空腸Treiz靭帯近位に憩室内潰瘍が認められた.ジクロフェナクを常用されており,NSAIDs関連腸管粘膜障害が考えられた.憩室内には腸管内容物が貯留しやすく,高濃度のNSAIDsが憩室内に停滞したことが,憩室内に粗大な潰瘍を形成した要因と考えられた.小腸に憩室が認められる症例に対してはNSAIDsの投与は慎重に行う必要がある.We report a rare case of multiple duodenal diverticula associated with ulcer accompanied by melena. …
NAID 120005246295

Related Pictures

★リンクテーブル★

リンク元	「下血」「血便」「黒色便」「blood in stool」「hemorrhagic stool」

「下血」

Melena
Classification and external resources
ICD-10	K92.1
ICD-9	578.1
MedlinePlus	003130

　　[★]

英: melena
ラ: melaena
同: タール便 tarry stool
関: 消化管出血(上部消化管出血、下部消化管出血)、黒色便、赤色便。吐血

定義

肉眼的に便に血液が混入する病態　　⇔　　潜血便潜出血 occult bleeding(肉眼的に血液混入がはっきりしない)
肛門からの血性排泄物を排泄すること

古典的：タール便(黒色を意味する)
臨床的：

(広義)便の中に血液が含まれている状態：黒色便、タール便、粘血便、鮮血便　　　(ただし潜血便は含まれない)
(狭義)タール便

狭義

症候名	便性状
下血	タール便	黒色便
血便	鮮血便	赤色便

下血

分類

頻度

IMD.566

疾患	頻度(%)
虚血性腸炎	26.4
抗菌薬起因性腸炎	16.4
大腸癌、大腸ポリープ	11.2
憩室炎	10
小腸より口側の出血	7.6
感染性腸炎	7.2
痔、裂肛	6.4
宿便性潰瘍	5.2
その他の腸炎	4
その他の出血	1.2
不明	4.4

出血部位と便の性状

IMD.567

暗褐色～赤褐色便	十二指腸	消化性潰瘍、乳頭部癌
	肝臓	肝癌
	胆道	胆道腫瘍、胆道炎
	膵臓	膵炎、膵癌
	小腸	クローン病、メッケル憩室、腸管動静脈血栓症、腸重積、感染性腸炎、結核、良悪性腫瘍
鮮紅色便	結腸	結腸癌、潰瘍性大腸炎、虚血性腸炎、ポリープ、憩室炎、悪性リンパ腫、薬物性腸炎、腸結核、S状結腸軸捻転、放射線腸炎
鮮紅色便	直腸～肛門	直腸癌、裂肛、痔核、ポリープ、潰瘍性大腸炎、放射線腸炎、子宮内膜症

「血便」

　　[★]

英: hematochezia, melena, bloody stool, hemorrhagic stool
関: 下血、消化管出血

[show details]

en

melena : 約 1,450,000 件
hematochezia : 約 126,000 件
bloody stool : 約 316,000 件
blood in stool : 約 1,390,000 件
hemorrhagic stool : 77 件

melena、hematochezia、bloody stool、blood in stool、hemorrhagic stool

血便

タール便
鮮血便：90%以上は痔疾患由来。
粘血便

定義

曖昧かもしれない。文献によって定義が異なる。

血液の付着または混入が肉眼で確実に認められる糞便。
赤い血液の混じった便　(消化器疾患ビジュアルブック p.12)　→　つまりは大腸由来の出血(大腸出血)を示唆。だが、小腸出血が多量ならばあり得るけどな。

原因

小腸：小腸腫瘍、クローン病、小腸潰瘍、メッケル憩室
大腸：大腸憩室、大腸アンギオディスプラジア、虚血性大腸炎、痔核、大腸癌、大腸ポリープ、潰瘍性大腸炎、クローン病、放射性直腸炎、細菌性腸炎

「黒色便」

　　[★]

英: black stool
同: タール様便 tarry stool、メレナ melena
関: 新生児メレナ