January 18, 2024 Author : Sofia Corredoura The stool laboratory tests are diagnostic tests which a doctor may request to help diagnose problems. There are several types of stools tests , such as blood testing, testing for eggs, cysts and parasites, stool cultures, pH or osmolarity measuring or quantifying fecal calprotectin. Various problems and digestive diseases may justify a stool test , namely: Infections caused by pathogens like bacteria, parasites and viruses that cause gastrointestinal disorders; Diseases that result in malabsorption of nutrients or weight loss; Suspicion of gastrointestinal bleeding, as may be the case with colorectal cancer among other causes of digestive bleeding. Some stool tests may be ordered routinely in certain age groups, others are required when there is a suspicion of something that could result in changes in the stool. In all cases, the results must be interpreted with other findings of the medical evaluation carried out, such as the clinical history and physical examination, and integrated with all the results of other tests that have been carried out or will be prescribed. Macroscopic observation This is an assessment of the appearance of feces and mainly concerns the appearance, color, presence of mucus, blood or other foreign substances, consistency, and shape. It is common to be performed along with other stool tests. Macroscopically normal stools are generally molded, with no traces of blood, mucus, pus, fat, undigested fibers, or microorganisms visible to the naked eye. However, the results of this observation cannot be interpreted alone: Often, changes in color, smell, consistency, or shape do not have any pathological cause, they simply reflect water consumption and the type of food eaten. When they are not normal, they may not be a single cause and, therefore, the results must be interpreted by the doctor and may even serve only to guide the ordering of other tests. Fecal occult blood test It is intended to check whether there is blood in the stool , in a small amount that is not visible to the naked eye. The presence of occult blood in the feces can be caused by digestive bleeding and this can have many origins, with very different severity. This exam is often requested from the age of 50 to screen for colorectal cancer in the intervals between successive colonoscopies. The result of the fecal occult blood test is positive or negative. Search for eggs, cysts, parasites and other microorganisms The presence of bacteria, parasites and viruses can be checked in feces . Depending on the type of microorganism, the analysis may involve direct observation of feces, microscope observation, cultures and search of DNA of the microorganism. Stool culture, or bacteriological examination of feces, is intended to check whether there are bacteria in the feces, such as Salmonella or other bacteria that cause fever, malaise, and diarrhea. The parasitological examination usually includes a macroscopic evaluation of the color and consistency of the feces and a microscopic evaluation with the purpose of identifying eggs, adult forms, or other forms of various parasites. Examples of parasitic infections include Giardia lamblia (giardiasis), pinworms (Enterobius vermicularis), roundworms (Ascaris lumbricoides) and some species of Taenia. Some parasites, or their eggs, are not eliminated continuously in the feces. In these cases, such as Giardia lamblia, several samples are requested to be collected on different days, generally 3 samples on alternate days. Parasite infections are more common in children, people or travelers from developing countries or in individuals with immune system disorders. Rotaviruses are a common cause of diarrhea in children and stool testing may also be required. The results of testing for microorganisms in feces are positive or negative. Other stool tests Other determinations can also be made in feces , generally to diagnose problems that interfere with the absorption of nutrients, such as: Increased fecal fat , which may be related to diseases of the pancreas, liver or bile ducts, inflammatory bowel disease, Giardiasis among other diseases that affect intestinal fat absorption; Increase in fecal calprotectin , which is a protein that is related to intestinal inflammation and that increases, for example, in inflammatory bowel disease. How is the stool sample collection done? In most cases, fecal collection is done at home and the container is taken to the laboratory. It is not necessary to fast for stool tests. Some other preparation may or may not be necessary before sample collection, depending on the test to be carried out. When necessary, it usually involves stopping some medications and avoiding certain foods. Also, depending on the test to be carried out, it may be necessary to obtain samples on several days, consecutive or alternate, which may or may not be mixed. To store stool samples, specific containers can be used that can be purchased at pharmacies. These containers are basically a wide-mouthed cup or tube that has a screw cap with a spatula or small spoon attached. It is important that the stool sample is not contaminated with urine or comes into contact with toilet water. Therefore, try to urinate before collecting the stool sample and follow all instructions given to you. Between collection and delivery of stool samples to the laboratory, they may need to be stored in the refrigerator, properly protected to avoid any contamination. Avoid touching feces with your hands and always wash your hands thoroughly: Before collecting the sample, particularly before handling the container where it will be stored; After closing and protecting the vial with the sample. The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
