Faecal occult blood test
Why this test?
- For the diagnosis of diseases of the gastrointestinal tract accompanied by violations of the integrity of the mucous membrane (ulcer disease of the stomach and duodenum, primary and metastatic tumors of the esophagus, stomach, large and small intestine, duodenal papilla, intestinal tuberculosis, nonspecific ulcerative colitis, helminthiasis).
- To assess the degree of damage to the mucous membrane of the gastrointestinal tract.
- To assess the adequacy of therapy for peptic ulcer disease, Crohn's disease, and intestinal tuberculosis. To assess the severity of the disease of the gastrointestinal tract and give further prognosis.
In what cases is it prescribed?
- With abdominal pain, heartburn, nausea, vomiting.
- With frequent mushy stools, false urges to defecate, constipation, abdominal pain, weight loss, loss of appetite, increased body temperature.
- When tumors of the gastrointestinal tract are detected (using instrumental methods) to rule out hidden bleeding of the gastrointestinal tract.
- When helminths are detected - to assess damage to the mucous membranes of the gastrointestinal tract. If the patient has previously been diagnosed with a stomach ulcer (non-specific ulcerative colitis, Crohn's disease, polyposis, intestinal tuberculosis).
Fecal occult blood analysis is an extremely important laboratory study in the diagnosis of occult bleeding from various parts of the gastrointestinal tract. Such bleeding is one of the early symptoms of a number of serious diseases of the gastrointestinal tract, including oncological ones. With hidden bleeding, even long-term, it is very difficult, and often simply impossible, to determine the presence of blood in the feces both visually and microscopically. With profuse bleeding from various parts of the gastrointestinal tract, blood changes the appearance of feces so much that its presence can often be determined visually. If the bleeding is from the lower parts of the intestines (colon, rectum), then the blood will be red, possibly in the form of clots or impurities. If the source of bleeding is in the upper parts of the gastrointestinal tract (part of the small intestine, esophagus, stomach), then the stool turns black, «tar-like» due to the interaction of blood and special enzymes that are produced in these parts of the gastrointestinal tract .
As a rule, if there are visual signs of bleeding from the gastrointestinal tract, then the situation is acute and requires emergency measures (emergency care). However, with less pronounced violations of the integrity of the mucous membrane of the gastrointestinal tract, with the involvement of a small number of vessels in the process, the color and consistency of feces do not change, but erythrocytes in the feces will be visible during microscopic examination. If microscopically, erythrocytes are not visible, and there is a suspicion of hidden bleeding, in this case, a fecal analysis for hidden blood is required. This study is carried out by measuring the amount of changed hemoglobin (and not the erythrocytes themselves). A positive stool reaction to occult blood means that a person has diseases of the gastrointestinal tract that cause a violation of the integrity of the mucosa, when a small amount of blood is released into the lumen of the stomach or intestine. This can occur with a stomach or duodenal ulcer, nonspecific ulcerative colitis, Crohn's disease, polyps, and helminth infestations.
Since tumors, primary and metastatic, cause damage to the mucous membrane of the gastrointestinal tract even at small sizes, the study is used at the first stage of detection of tumors of the gastrointestinal tract. It is especially important to determine occult blood in the diagnosis of colon cancer, since it is precisely with tumors in this part of the intestine that occult bleeding begins in the earliest stages. Blood in the stool can also be detected with nosebleeds, bleeding from the gums and pharynx, in patients with varicose veins of the esophagus, erosive esophagitis, hemorrhoids and other diseases, so it is necessary to take this into account when evaluating the results of the analysis.
The reliability of the analysis is highest when it is repeated. Negative test results do not exclude the possible presence of an erosive-ulcerative or tumoral lesion of the gastrointestinal tract in the patient. It is important that the results should be evaluated in combination with other instrumental and laboratory tests, as they cannot be the only criterion for making a diagnosis by themselves. Sometimes the entire examination of feces for occult blood is mistakenly called a test or Gregersen's reaction, erroneously - because the Gregersen's reaction (benzidine test both) is the most common, but not the only, method of detecting hidden blood in feces, urine, vomitus, etc.