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Fecal occult blood testing (FOBT), as its name implies, aims to detect subtle blood loss in the gastrointestinal tract, anywhere from the mouth to the colon.Positive tests ("positive stool") may result from either upper gastrointestinal bleeding or lower gastrointestinal bleeding and warrant further investigation for peptic ulcers or a malignancy (such as colorectal cancer or gastric cancer).
The presence of bright red blood in stool, known as hematochezia, typically indicates lower gastrointestinal bleeding. Digested blood from the upper gastrointestinal tract may appear black rather than red, resulting in "coffee ground" vomit or melena. [2] Other signs and symptoms include feeling tired, dizziness, and pale skin color. [18]
Occult blood may refer to: Fecal occult blood, blood present in the feces that is not visibly apparent; Hematuria, the presence of red blood cells in the urine
The stool guaiac test involves fasting from iron supplements, red meat (the blood it contains can turn the test positive), certain vegetables (which contain a chemical with peroxidase properties that can turn the test positive), and vitamin C and citrus fruits (which can turn the test falsely negative) for a period of time before the test.
The American College of Gastroenterology has recommended the abandoning of gFOBT testing as a colorectal cancer screening tool, in favor of the fecal immunochemical test (FIT). [3] The newer and recommended tests look for globin, DNA, or other blood factors including transferrin, while conventional stool guaiac tests look for heme.
Blood in stool looks different depending on how early it enters the digestive tract—and thus how much digestive action it has been exposed to—and how much there is. The term can refer either to melena, with a black appearance, typically originating from upper gastrointestinal bleeding; or to hematochezia, with a red color, typically originating from lower gastrointestinal bleeding. [6]
Depending on the amount of the blood loss, symptoms may include shock. Upper gastrointestinal bleeding can be caused by peptic ulcers, gastric erosions, esophageal varices, and rarer causes such as gastric cancer. The initial assessment includes measurement of the blood pressure and heart rate, as well as blood tests to determine the hemoglobin.
Hematuria can be classified according to visibility, anatomical origin, and timing of blood during urination. [1] [6]In terms of visibility, hematuria can be visible to the naked eye (termed "gross hematuria") and may appear red or brown (sometimes referred to as tea-colored), or it can be microscopic (i.e. not visible but detected with a microscope or laboratory test).
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