Fecal occult blood may originate in any of the organs of the digestive tract.
Melena (glossy black, soft, pasty stool) usually indicates an upper gastrointestinal hemorrhage, ie bleeding coming from the esophagus, stomach, duodenum, jejunum possible. Thus hemoglobin is converted under the action of digestive juices to hematin, which is found in the feces. Hematochezia (red blood issued as such, alone or mixed with feces) is suggestive of a hemorrhage that occurred in the terminal portion of the intestine, meaning in the rectum, colon, possibly in the ileum (ulcerative colitis, Crohn’s disease, colorectal carcinoma, polyps ). Determination of occult hemorrhage is a screening blood test particularly important for preventive medicine. Numerous studies have shown that regular use of this test, alone or together with sigmoidoscopy significantly reduces mortality from colorectal cancer.
The test is used as screening for colorectal cancer; however, not every colorectal bleeding is due to precancerous or cancerous polyps.
Negative results do not exclude bleeding, which may be intermittent.
False positive: Fecal contamination with menstrual blood or urine hematuria
Positive reactions: drugs that cause gastrointestinal bleeding: aspirin, corticosteroids, NSAIDs (indomethacin, ibuprofen, sulindac); drugs that cause colitis (ex .: methyldopa and some antibiotics):
Recommendations for determining occult hemorrhage (occult bleeding):
– Screening of asymptomatic patients in order to detect colorectal cancer (annual performance test is recommended in patients over 45-50 years);
– Suspicion of upper and lower gastrointestinal hemorrhage (regardless of etiology: benign or malignant) in patients with abdominal discomfort, alteration in bowel habits, recent weight loss or unexplained chronic iron deficiency anemia;
Training patient – no special training is required (since this is an immunological test, it is necessary to respect a diet before bleeding).
Collected specimens – feces collected at any time of the day.