What is the stool test used for?

There are different methods to analyze a stool sample and detect possible abnormal presences such as polymorphonuclear feces.

What is detected with a stool test?

The analysis of feces is one of the most basic, useful and commonly used tools in the field of Medicine because the technique of obtaining the sample is simple and safe and the analysis of the sample by provides a very valuable information about the health status of the person.

It allows diagnosing the presence of localized infections in the intestinal tract What:

• bacterial infections that cause diarrheal syndromes or parasite infections.
• Detect the presence of blood typical of inflammatory, infectious or tumor processes of the digestive tract.
• Suspect the presence of intestinal malabsorption syndromes or inflammatory bowel diseases such as Cronh's disease, among many other processes, which must later be confirmed later through specific studies for each of them.

How to collect a stool sample?

The study of stool requires the taking of a stool sample by the patient. In most cases, sample collection can be done the patient himself at home.

• The collection of feces requires a adequate intimate hygiene by cleaning the perianal area and external genitalia with soap and water.
• The patient must urinate prior to defecation since feces mixed with urine will not be useful for the study as they may be contaminated by germs from the urinary tract.
• The patient should proceed to a new intimate cleaning after urination and before proceeding to defecation.

There are different methods for collecting samples but the patient is usually advised to use a plastic stool collector sterile (sold in pharmacies) that is placed on the bidet or on a previously disinfected container.

• The patient should avoid using your hands to avoid contaminating the sample so you should help yourself by using latex gloves or a spatula for collection.
• The amount of sample needed the doctor will indicate it according to the type of study to be performed: a small quantity and a single sample for the biochemical study or the occult blood study and a larger quantity and several consecutive samples for other more complex studies such as the search for fat or parasites in stool.
• Once the stool sample has been collected, the patient must deliver the closed container as soon as possible and within 24 hours at the center where the study has been requested, and from there it will be sent to a specialized laboratory for analysis.
• The sample can be kept in the refrigerator in the closed container until delivery.

Pre-study preparation and contraindications

Stool analysis does not require any special preparation on the part of the patient.

The woman should avoid taking the sample as much as possible during menstruation to avoid the presence of blood in the stool that could lead to a misinterpretation of the results. Certain studies will require special conditions such as avoid taking certain foods or drugs the days prior to the collection of samples or the collection of three or more consecutive stool samples, among others; in any case, the doctor must indicate these special conditions to the patient.

The collection of stool samples is carried out by normal defecation by the patient and therefore does not imply any kind of discomfort for the same.

The study does not imply any type of risk for the patient and does not exist No kind of contraindication.

Special stool stains or studies

In general lines and depending on the analysis method used, the study of feces can be classified into the following types.

Methylene blue stain or Wright's stain

It allows to detect the presence of leukocytes polymorphonuclear cells in stool (characteristic alteration of bacterial infectious processes or intestinal inflammatory diseases).

Sudan staining

It allows detecting the presence of fat in the stool (a characteristic alteration of intestinal malabsorption syndromes).

Biochemical study

It includes the analysis of the general characteristics of feces: color, consistency, pH, enzymes ... It is the basic study of feces.

Occult blood in stool or guaiac test

Analysis of a small sample of stool carried out in the laboratory or sometimes in the doctor's office, allows to detect the presence of small amounts of blood mixed with feces (hematochezia) usually not visible to the human eye.

Hidden blood in stool using disposable reagents

Available in some countries over the counter in pharmacies, these are test strips that in contact with feces allow detecting the presence of occult blood in the feces at the patient's home. It is used as a screening test.

Microbiology, microbiological analysis of feces or stool culture

It is carried out through the use of different laboratory techniques, it allows to know if it exists and the type of germ involved, as well as to establish the different antibiotics to which the detected germ is sensitive through what we know as an antibiogram.

Egg hunt and parasites

It is carried out through the use of different laboratory techniques, it allows to detect the presence of larvae and eggs in feces and identification of the parasite.

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Dra. Cristina Muñoz Gil Family and Community Medicine Specialist