Black stool, why is that happened? Let me tell you

Black stool, in medicine we call it melena. melena or melæna refers to the black, "tarry" feces that are associated with gastrointestinal hemorrhage.[1] The black color is caused by oxidation of the iron in hemoglobin during its passage through the ileum and colon.

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 enzymatic breakdown is associated with melena. For this reason, melena is often associated with blood 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 although, as noted below, exceptions occur with enough frequency to render it unreliable. Blood in the stool may come from anywhere along your digestive tract, from mouth to anus. It may be present in such small amounts that you cannot actually see it, and it is only detectable by a fecal occult blood test. When there is enough blood to change the appearance of your stools, the doctor will want to know the exact color to help find the site of bleeding. To make a diagnosis, your doctor may use endoscopy or special x-ray studies. Black stool usually means that the blood is coming from the upper part of the gastrointestinal (GI) tract. This includes the esophagus, stomach, and the first part of the small intestine. Blood will typically look like tar after it has been exposed to the body's digestive juices as it passes through the intestines. Maroon-colored stools or bright red blood usually suggests that the blood is coming from the lower part of the GI tract (large bowel, rectum, or anus). However, sometimes massive or rapid bleeding in the stomach causes bright red stools. Eating black licorice, lead, iron pills, bismuth medicines like Pepto-Bismol, or blueberries can also cause black stools. Beets and tomatoes can sometimes make stools appear reddish. In these cases, your doctor can test the stool with a chemical to rule out the presence of blood. Bleeding in the esophagus or stomach (such as with peptic ulcer disease) can also cause you to vomit blood. In some patients bleeding can be black and "tarry" (sticky) and foul smelling. The black, smelly and tarry stool is called melena. Melena occurs when the blood is in the colon long enough for the bacteria in the colon to break it down into chemicals (hematin) that are black. Therefore, melena usually signifies bleeding is from the upper gastrointestinal tract (for example: bleeding from ulcers in the stomach or the duodenum or from the small intestine) because the blood usually is in the gastrointestinal tract for a longer period of time before it exits the body. Sometimes melena may occur with bleeding from the right colon. On the other hand, blood from the sigmoid colon and the rectum usually does not stay in the colon long enough for the bacteria to turn it black. Rarely, massive bleeding from the right colon, from the small intestine, or from ulcers of the stomach or duodenal can cause rapid transit of the blood through the gastrointestinal tract and result in bright red rectal bleeding. In these situations, the blood is moving through the colon so rapidly that there is not enough time for the bacteria to turn the blood black. Symptoms Patients sometimes present with signs of anemia or those due to low blood pressure. Very often, however, aside from the melena itself, there are no other symptoms. 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. 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. Note: As iron is the source of the black color, consumption of black pudding may cause asymptomatic melena. Why is that happened? 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. It is also caused by tumours, especially malignant tumors affecting the esophagous, 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 tumours is haematemesis. It may also accompany hemorrhagic blood diseases (e.g. purpura & hemophilia). Other medical causes of melena include bleeding ulcers, gastritis, esophageal varices, and Mallory-Weiss syndrome. Some 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 the traditional African Maasai diet, which includes much blood drained from cattle. Melena is usually not a medical emergency because the bleeding is slow. Urgent care however 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. The upper part of the GI tract will usually cause black stools due to: Abnormal blood vessels (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 The lower part of the GI tract will usually cause maroon or bright red, bloody stools due to: Anal fissures Bowel ischemia (when blood supply is cut off to part of the intestines) Colon polyps or colon cancer Diverticulosis (abnormal pouches in the colon) Hemorrhoids (common cause) Inflammatory bowel disease (such as Crohn's disease or ulcerative colitis) Intestinal infection (such as bacterial enterocolitis) Small bowel tumor Trauma or foreign body Vascular malformation (abnormal collections of blood vessels called arteriovenous malformations or AVMs) How to treat this? If you have passed a lot of blood, you may need emergency treatment, which can include: Blood transfusions Fluids through a vein Interventional radiography embolization (a procedure to block the blood vessels that may be bleeding) Medications to decrease stomach acid Possible surgery if bleeding does not stop