Learning Objectives
By the end of this section, you will be able to:
- Describe the chemical, physical, and microscopic characteristics of stool
- Verbalize the steps in collecting a stool specimen
- Interpret the results of a stool specimen
In the ever-evolving field of health care, comprehensive knowledge and proficiency in nursing skills are critical for providing high-quality patient care. One fundamental aspect of patient assessment and diagnosis revolves around understanding the intricacies of feces both as a diagnostic tool and as a reflection of an individual’s gastrointestinal health. The solid waste product that is expelled from the body through the rectum and anus during the process of defecation is called feces (also commonly referred to as stool or bowel movements). This section delves into the essential aspects of the chemical, physical, and microscopic characteristics of stool. You also learn how to accurately collect a stool specimen to send for analysis. Nurses must be able to interpret the results of a stool sample, equipping them with the expertise needed to make informed clinical decisions and deliver the best possible care to patients.
Stool Specimen Overview
A stool specimen, also known as a fecal specimen or fecal sample, is a sample of feces (solid waste) collected from a person for laboratory analysis. Components of stool specimen analysis include chemical analysis, physical characteristics, and microscopic examination.
Chemical analysis of stool involves the laboratory examination of a stool sample to assess its composition and detect specific substances or markers that can provide valuable diagnostic information about a person’s gastrointestinal health. Stool samples may be analyzed for various chemicals, including fat, carbohydrates, and enzymes, to assess digestive function and nutrient absorption.
Chemical analysis may be used to detect blood, measure the amount of fat in the stool, identify the presence of reducing substances, measure stool pH, assess stool urobilinogen, assess stool bile acids, and assess stool nitrogen content.
Physical assessment of stool involves the visual and sensory examination of stool characteristics, including color, consistency, shape, odor, mucous, undigested food particles, parasites or worms, and blood. The physical characteristics of stool provide information about gastrointestinal health, and abnormalities in these characteristics may indicate digestive disorders.
Microscopic assessment of stool involves examining a stool sample under a microscope to identify and evaluate various components, including cells, microorganisms, and particles. Cultures may be performed to identify specific pathogens, such as bacteria, viruses, parasites, or fungi.
Purpose
Stool specimens are commonly used in clinical diagnostics to evaluate various aspects of gastrointestinal health and to detect the presence of certain diseases or conditions. For example, stool specimens are often collected to diagnose infections, inflammatory bowel disease (IBD), and malabsorption disorders. Stool samples may also be used to detect infections caused by bacteria, viruses, parasites, and fungi that can affect the digestive tract. Common examples include bacterial gastroenteritis, Clostridium difficile infection, and intestinal parasitic infections. Stool specimens may be collected at various points during treatment to assess the effectiveness of therapies, such as antibiotics for bacterial infections or antiparasitic medications. They may also be examined for the presence of occult blood (hidden blood), which may indicate gastrointestinal bleeding from conditions like ulcers or colorectal cancer, and to provide insights into digestive function, including the presence of pancreatic enzymes and the ability to absorb certain nutrients.
Types of Stool Collection
There are several types of stool collection methods, each designed for specific diagnostic purposes. The choice of stool collection method depends on the clinical need and the type of analysis required. Common types of stool sample collections include random stool sample, three-day stool collection, fecal occult blood test (FOBT), stool culture, stool for ova and parasites (O&P), stool fat test (fecal fat test), and stool for Clostridium difficile (C. diff) toxin. Descriptions of each can be found in Table 10.4.
| Type of Stool Collection | Description of the Collection Method |
|---|---|
| Random stool sample | A single stool sample collected at any time without specific timing or preparation. It is often used for routine tests, such as checking for the presence of blood or infectious agents in the stool. |
| Three-day stool collection | For some tests, a healthcare provider may request stool samples collected over a period of three consecutive days. This method can help detect intermittent problems or infections that may not be present in a single sample. |
| Fecal occult blood test (FOBT) | This test is used to detect small amounts of blood in the stool, which may be indicative of gastrointestinal bleeding. The sample is typically collected on special cards or slides. |
| Stool culture | A stool culture is used to identify and isolate specific bacteria or pathogens causing gastrointestinal infections. A fresh stool sample is collected and sent to a laboratory for bacterial culture. |
| Stool for ova and parasites (O&P) | This test is used to identify the presence of parasites or their eggs in the stool, such as Giardia or Entamoeba histolytica. Multiple stool samples may be collected on different days for accurate diagnosis. |
| Stool fat test (fecal fat test) | This test measures the amount of fat in the stool and is used to diagnose malabsorption disorders, such as celiac disease or chronic pancreatitis. It may involve collecting stool samples over a twenty-four- to seventy-two-hour period while on a specific diet. |
| Stool for Clostridium difficile (C. diff) toxin | This test detects the presence of C. difficile toxins in the stool and is used to diagnose C. difficile infection, especially in cases of antibiotic-associated diarrhea. |
Procedural Steps for Stool Collection
Properly collecting a stool sample is crucial for accurate test results and contamination prevention. To prepare, gather necessary supplies, explain the procedure to the patient, and ensure privacy. Identify the patient with name and date of birth, matching with patient verbally and checking ID bands. Preprinted labels should be verified too. Wear gloves, place a collection device in the toilet, and instruct the patient to avoid water contact during sample collection. Advise against placing toilet paper in the container. Collect a walnut-sized stool portion, avoiding urine contamination. Securely close and label the container with patient details, date, and time. Dispose of any used plastic wrap, clean the toilet, remove gloves, and wash hands thoroughly.
Clinical Safety and Procedures (QSEN)
QSEN Competency: Collecting a Random Stool Sample
See the competency checklist for Collecting a Random Stool Sample. You can find the checklists on the Student resources tab of your book page on openstax.org.
Clinical Judgment Measurement Model
Generate Solutions: Recognizing Potential Contamination of a Stool Sample
The nurse is collecting a stool sample from a plastic collection device that was placed underneath the toilet seat. While collecting the sample, the nurse notes a small amount of yellow liquid in the plastic container (recognizing cues). Provided the plastic collection container was placed under the toilet seat, the nurse realizes that urine may have accidentally gotten in the collection container. The nurse asks the patient if they urinated during the collection process, which the patient confirmed they had (analyzing cues). The nurse suspects the stool was contaminated with urine (prioritize hypotheses) and decides the sample needs to be recollected (generate solutions).
For the collection of a stool sample to test for occult blood, gather a fecal occult blood card (card containing a testing area that changes color when it comes into contact with blood), gloves, and an applicator stick or brush. Follow the same procedures for collecting a stool sample; however, use the applicator stick or brush to collect a small sample of stool from different areas of the bowel movement. Occult blood is not typically equally dispersed throughout the stool; therefore, taking samples from different areas of the bowel movement increases the chances of identifying blood that may be present. Follow the instructions in the kit for how many samples to collect and where to collect them. Avoid urine contamination and transfer the collected stool samples onto special test cards. Seal the test cards according to the kit’s instructions. This may involve folding the card or attaching a special sticker. Label the sample with the patient’s name, date of birth, date, time, and any other information requested on the test card or container label. Clean up, dispose of gloves, and wash hands. If you are working in a facility where nurses apply the fecal occult developer solution to the card, allow the specimen to dry for three to five minutes. Open the reverse side of the card and apply two drops of fecal occult developer solution to each square. A blue reaction will occur within sixty seconds if the test is positive. The absence of a blue color after sixty seconds is considered a negative test.
Clinical Safety and Procedures (QSEN)
QSEN Competency: Collecting a Fecal Occult Blood Test and Hemoccult Card
See the competency checklist for Collecting a Fecal Occult Blood Test and Hemoccult Card. You can find the checklists on the Student resources tab of your book page on openstax.org.
Transport the sample following the instructions provided by the healthcare facility’s protocols. Some samples may need to be refrigerated during transport, while others can be stored at room temperature. Prompt delivery to the laboratory is essential for accurate results. The specific instructions for collecting stool samples may vary depending on the test and healthcare provider’s requirements. It is essential to follow the provided instructions carefully to ensure the accuracy and reliability of the test results.
Documentation of Stool Collection
Documenting a stool sample is essential for maintaining accurate records and ensuring proper tracking of the sample throughout the diagnostic process. Proper documentation helps healthcare providers and laboratory personnel to associate the sample with the correct patient, record relevant information, and interpret results correctly.
Document the date and the time when the stool sample was collected. Indicate the specific stool collection method used, such as a random sample, twenty-four-hour collection, or FOBT. Document any other relevant details, such as any unusual characteristics of the stool. If the stool sample collection required special instructions, such as dietary restrictions or medication adjustments, make sure these instructions are documented clearly. Note if the sample was difficult to collect or if there were any issues during the collection process.
Patient Education
Many medications can alter the results of stool tests; therefore, patients may need to avoid certain medicines prior to the stool testing. Patients should be educated to stop taking medicines such as antacids, antidiarrheal medicines, antiparasitic medicines, antibiotics, laxatives, or nonsteroidal anti-inflammatory drugs (NSAIDs) for one to two weeks before stool testing. For example, antacids may alter the pH of the stool, which may affect the chemical reactions of the testing, leading to false-negative occult blood testing or decreased detection of bacteria. NSAIDS may cause changes in stool consistency (diarrhea) and gastrointestinal irritation that may result in false-positive occult blood testing.
If the patient is self-collecting the stool sample, they should be educated on the proper procedure for collecting the sample and how to store the sample once it is collected. Patients should be instructed to ensure the stool is not mixed with urine, toilet paper, or any other contaminants. It is important to educate the patient on the importance of collecting a fresh sample, keeping the sample in a cool, dry place (not in the refrigerator), and returning the sample to the laboratory as soon after collection as possible. If the sample is being tested for blood, instruct the patient to avoid the test if they have active bleeding or it is during their menstrual cycle, as these may lead to a false-positive result. Patients should also be instructed to avoid red meats for three days prior to testing, as the blood from the meat can cause a false-positive test result.
Patient Conversations
Educating Patients on How to Collect a Stool Sample
Nurse: Good morning, Mr. Hall. Your provider has ordered a stool sample to see if we can figure out what is causing your stomach pain. I’m here to provide you with some instructions on how to collect the stool sample and will guide you through the process.
Patient: Good morning. I appreciate your help. I’ve never done this before, so I’m a bit unsure about how it all works.
Nurse: That’s completely understandable, Mr. Hall. First, this is the stool collection kit [shows the kit to the patient]. It contains everything you need. Here, we have a collection container, a wooden stick, and a pair of disposable gloves [shows each item to the patient as the item is identified].
Patient: Okay, what do I do with those items?
Nurse: First, you will put on the disposable gloves. This is to ensure neither your hands nor the sample get contaminated with stool. Next, place a piece of plastic wrap under the toilet seat to catch the stool. This makes it easier to collect the stool without any contact with urine or toilet water. When you’re ready to have a bowel movement, pass the stool onto the plastic wrap. Then use the wooden stick to scoop the stool into the collection container. You only need a small amount, about the size of a walnut, so you don’t have to fill the container to the top. It is important, though, to collect the sample while it’s still fresh and be sure not to put the toilet paper in with the stool. Remove your gloves, turning them inside out to avoid contact with the stool.
Place the lid tightly on the collection container, place the container into the provided plastic bag, and seal it tightly.
Patient: That doesn’t seem too hard. What do I do once I’ve collected the sample?
Nurse: Once you’ve collected the sample and securely packaged it in the plastic bag, please label the bag with your name, birth date, date of collection, and the time the sample was collected. Store the sample in a cool, dry place until you bring it to the lab. Ideally, it should be taken to the lab as soon as possible for accurate testing. Make sure not to refrigerate the sample unless specified by your healthcare provider.
Patient: I appreciate you walking me through what to do. This makes the process seem much less intimidating.
Nurse: I’m glad I could help, Mr. Hall. If you have any more questions or concerns as you go through this process, please don’t hesitate to reach out. We’re here to assist you every step of the way.
Interpretation of Results
Interpreting stool test results involves analyzing the data obtained from various laboratory tests performed on a stool sample. The interpretation is done by healthcare professionals, such as gastroenterologists, pathologists, or primary care physicians, in the context of the patient’s medical history, symptoms, and clinical presentation. Interpretation of stool test results should always consider the entire clinical context, including the patient’s symptoms, medical history, physical examination, and other diagnostic tests. Depending on the findings, further tests and evaluations may be recommended to determine the underlying cause of any abnormalities and to develop an appropriate treatment plan.
Normal Findings
Normal stool should appear brown, soft, well-formed in consistency, and shaped like a tube. It should have a stool-like odor due to the bacteria in the gut; however, it should not be overpowering. Normal stool should not contain blood, mucus, pus, undigested meat fibers, harmful bacteria, viruses, fungi, or parasites. However, undigested food particles in stool may be normal in some circumstances, especially after consuming certain foods like corn or seeds.
A normal FOBT result is negative, indicating the absence of occult (hidden) blood in the stool. A normal fecal fat test shows minimal to no fat content in the stool, indicating the individual is efficiently digesting and absorbing dietary fats. Minimal or no reducing substances should be present in the stool, indicating efficient carbohydrate digestion and absorption. The stool pH should fall within a normal range which can vary but is typically slightly acidic or neutral, reflecting normal gastrointestinal function. A normal stool urobilinogen level is present, indicating the normal metabolism of bilirubin in the intestines. Normal levels of bile acids are found in the stool, suggesting proper bile production and flow.
Under the microscope, normal stool should contain a minimal number of white blood cells (leukocytes) (indicating the absence of significant inflammation or infection in the gastrointestinal tract) and no red blood cells (erythrocytes) (indicating the absence of gastrointestinal bleeding). Epithelial cells from the lining of the gastrointestinal tract may be present but in small quantities. Normal stool may contain some bacteria, predominantly the normal gut flora, which includes various types of bacteria. Yeast cells or fungi should be rare. Stool samples are typically negative for parasites. Normal stool may contain a minimal amount of fat, but fat should not be present in large quantities (which suggests efficient fat digestion and absorption).
Abnormal Findings
Abnormal stool may be black (may indicate upper gastrointestinal bleeding or iron supplement ingestion), red (may indicate lower gastrointestinal bleeding), white (may indicate liver or biliary disorders), yellow (may indicate malabsorption of fats), or green (may indicate infection or malabsorption). It may be watery or loose (diarrhea) or hard, dry pellets (constipation) (Figure 10.3). Stools that are thin in shape may indicate a narrowing in the colon (which may indicate colon cancer). Foul-smelling stools can result from certain infections, malabsorption, or dietary factors. Odor changes may indicate an underlying issue. Increased mucus production or visible mucus may be associated with conditions like irritable bowel syndrome (IBS) or IBD. Persistent undigested food in stool could indicate malabsorption or gastrointestinal disorders.
Abnormal stool may contain blood, mucus, pus, undigested meat fibers, harmful bacteria, viruses, fungi, or parasites. The presence of visible blood in stool (hematochezia) or occult blood (hidden blood) may indicate gastrointestinal bleeding, which can have various causes, including ulcers, hemorrhoids, or colorectal cancer. Hematochezia is often associated with melena, which is dark, tarry stools, often associated with upper gastrointestinal bleeding. The dark color results from the digestion of blood as it travels through the digestive system. Melena is considered a medical emergency and requires prompt evaluation and intervention by healthcare professionals.
Abnormal chemical assessments of the stool may also help to identify gut health. A positive FOBT result indicates the presence of occult blood in the stool, which may suggest gastrointestinal bleeding. Blood noted in the stool should be immediately reported to the provider for further evaluation. Elevated levels of fat in the stool (steatorrhea) are abnormal and may suggest malabsorption disorders, such as celiac disease, chronic pancreatitis, or conditions affecting fat digestion and absorption. Elevated levels of reducing substances (carbohydrates) in the stool are abnormal and may suggest carbohydrate malabsorption or lactose Intolerance. Stool pH that is consistently highly acidic or alkaline may be abnormal. Elevated levels of urobilinogen in the stool may be abnormal and may suggest liver disease or other conditions affecting bilirubin metabolism. Elevated levels of bile acids in the stool may be abnormal, indicating malabsorption disorders or problems with the biliary system.
When the stool is examined under the microscope, elevated numbers of white blood cells (leukocytes) in stool may indicate inflammation, infection, or certain gastrointestinal disorders. The presence of red blood cells (erythrocytes) can be a sign of gastrointestinal bleeding. Abnormal microorganisms, such as pathogenic bacteria, Clostridium difficile (C. difficile) spores, or excessive yeast/fungi, may be present (which may indicate infections or imbalances in the gut microbiome). Detection of parasites like Giardia, Entamoeba histolytica, or other pathogenic parasites is abnormal. Abnormally high numbers of fat globules (steatocytes) in the stool may suggest malabsorption disorders, such as celiac disease, chronic pancreatitis, or fat digestion issues.
Abnormal assessment findings of stool may require further evaluation by a healthcare provider, often involving additional tests and diagnostic procedures to identify and address underlying gastrointestinal issues or diseases. Interpretation of these results should be done in the context of the patient’s clinical history and presentation.
Factors Affecting Results
Stool test results can be influenced by various factors, including the patient’s diet, medications, underlying medical conditions, and even the timing of the sample collection. It is essential to be aware of these factors, as they can impact the accuracy and interpretation of stool test results (Table 10.5).
| Factor | Affecting Result |
|---|---|
| Medications, such as anticoagulants, colchicine, nonsteroidal anti-inflammatory medicines (NSAIDs), iron preparations, corticosteroids, and phenylbutazone | May irritate the gastric mucosa and cause a positive occult blood result |
| Antibiotics | Can alter the gut microbiome |
| Vitamin C | Can cause a false-negative occult blood result |
| Constipation (prolonged exposure to intestinal bacteria) | May not show trypsin activity |
| Red meat, certain fruits (apples, bananas, cantaloupe), and vegetables (broccoli, cauliflower, radishes, and turnips) | Can cause a false-positive occult blood result |
| Specimen contamination (urine, water, toilet paper) | Compromises the integrity of the sample |
The timing of sample collection can be critical for certain stool tests. For example, for FOBTs, samples collected during menstruation or immediately after gastrointestinal bleeding may yield false-positive results. Incorrect handling, storage, or transportation of stool samples can introduce contamination and affect the integrity of the sample. Inadequate or improper collection techniques can lead to inaccuracies in stool test results.
To ensure the accuracy and reliability of stool test results, it is essential to follow specific instructions provided by healthcare providers or laboratories. Additionally, healthcare providers should consider the patient’s clinical history and any influencing factors when interpreting stool test results and making diagnostic and treatment decisions.