Fecal examination is a common medical examination method that provides us with information about the digestive system, gut microbiota, and other aspects by analyzing fecal samples. So, is fecal testing reliable for diagnosing diseases? This article will introduce you to the relevant knowledge of fecal testing, giving you a more comprehensive understanding of this examination method.
1、 The role of fecal examination
Fecal examination helps doctors understand whether patients have inflammation, bleeding, parasitic infections, malignant tumors, etc. in the digestive tract by examining the composition, characteristics, and cells of fresh feces. Based on the characteristics and composition of feces, it indirectly determines the functional status of the gastrointestinal, pancreatic, and hepatobiliary systems, and checks for pathogenic bacteria in feces to assist in the diagnosis of intestinal infectious diseases. Fecal examination can reflect the integrity of the intestinal mucosa, the balance of intestinal microbiota, and the presence of potential infections.
2、 The method of fecal examination
1. Visual observation: Observing the appearance, color, characteristics, quantity, etc. of feces can provide a preliminary understanding of intestinal function and make a preliminary judgment on diseases. For example, fresh stool indicates gastrointestinal bleeding, nodular hard stool is seen in habitual constipation, and increased mucus on feces indicates intestinal irritation or inflammation.
2. Microscopic examination: Direct fecal smear microscopy is a routine clinical examination item. Through microscopic examination, many pathological changes that cannot be observed by the naked eye can be discovered, and pathological components such as various cells, parasite eggs, fungi, bacteria, protozoa, etc. can be found. Various food residues can also be observed to understand digestion and absorption functions.
3. Chemical examination: For example, fecal occult blood test, which uses chemical methods to detect small amounts of gastrointestinal bleeding that cannot be confirmed by naked eye or microscope. Can help detect intestinal bleeding.
4. Immunological examination: Immunological methods can be used to detect specific antigens or antibodies in feces, such as rotavirus antigen.
5. Molecular biology examination: Specific pathogenic microorganisms such as Clostridium difficile can be detected in feces through molecular biology techniques such as polymerase chain reaction (PCR).
6. Fecal culture examination: There should be a large number of bacteria in normal stool, but mainly Escherichia coli, which belongs to the main parasitic bacteria in the intestine and can form a normal bacterial community. It has the function of maintaining intestinal digestion and absorption, and resisting external bacteria. The significance of fecal culture examination is to clarify whether the examiner's stool is mainly parasitic on Escherichia coli. If Salmonella is the main parasitic bacterium, it can indicate the presence of typhoid fever in the test taker. If Shigella is the main parasitic bacterium, it mostly indicates bacterial dysentery in the test taker.
3、 Scope of application of stool examination
1. Digestive system diseases: digestive system symptoms such as diarrhea, abdominal pain, nausea, vomiting, etc. Fecal examination can help determine the cause, such as bacterial infection, viral infection, parasitic infection, etc.
2. Imbalance of gut microbiota: Imbalance of gut microbiota can lead to symptoms such as constipation and diarrhea. Fecal examination can help doctors determine the balance of gut microbiota.
3. Inflammatory bowel disease: such as ulcerative colitis, Crohn's disease, etc. The diagnosis of these diseases usually requires multiple stool tests to observe changes in their characteristics and composition.
4. Intestinal parasitic infections: Fecal examination can help detect intestinal parasitic infections such as roundworm disease, hookworm disease, whipworm disease, pinworm disease, ginger leaf worm disease, tapeworm disease, schistosomiasis, etc. The diagnosis can be determined by finding the corresponding eggs in the stool smear.
5. Digestive tract tumors: Persistent positive fecal occult blood often indicates malignant tumors of the gastrointestinal tract, intermittent positive, indicating gastrointestinal bleeding of other reasons. Further endoscopic examination or barium meal imaging of the gastrointestinal tract can be performed.
6. Hepatobiliary and pancreatic diseases: Some hepatobiliary and pancreatic diseases may cause changes in the color and characteristics of feces, such as cholestatic jaundice, white clay colored feces, hemolytic jaundice, dark yellow feces, and pancreatitis may lead to fat diarrhea.
7. Other systemic diseases: Some autoimmune diseases, endocrine diseases, etc. may also affect the digestive system, leading to abnormal digestive function. In these cases, fecal testing is also necessary.
4、 Limitations of fecal testing
1. Low specificity: Some diseases may not have obvious gastrointestinal symptoms in the early stages, and fecal testing may not be able to detect these potential issues.
2. Subjective influence: The results of fecal testing may be influenced by the subjective judgment of the examiner, such as differences in descriptions of characteristics, colors, etc.
3. Limited scope of examination: Fecal examination can only reflect the condition inside the intestine, and cannot make accurate judgments on lesions outside the intestine.
4. False positives and false negatives: When examining fecal occult matter, try to avoid using vitamin C, iron, minerals, liver, tobacco, chlorophyll rich vegetables, and iron containing foods for 3 days before collecting the specimen to avoid false negative or false positive results during the examination.
In summary, fecal testing, as a non-invasive examination method, plays an important role in the diagnosis of digestive system and related diseases. However, we cannot rely solely on the results of stool tests to make a final diagnosis. In clinical practice, doctors need to make a comprehensive judgment based on the patient's medical history, physical examination, other laboratory and imaging examination results.