Diagnostics > Stool Tests

Stool sample basics: All you need to know

Dr. med. Andre Sommer

Dr. med. Andre Sommer

The examination known as a “stool sample” includes various diagnostic tests that examine the patient's stool. It may be necessary for various illnesses, such as for the microbiological examination of stool in the event of diarrhea to detect bacteria or parasites. Another example is to test for blood in the stool, which can be used for suspected bleeding in the gastrointestinal tract and in the context of cancer screening. Stool examinations are also carried out if suspected irritable bowel syndrome or inflammatory bowel disease is present in order to initially rule out possible other causes of diarrhea.

How do I take a stool sample?

Step 1:

Stop taking any medications that may affect the sample. This includes medication that softens your stool. For example, medications for heartburn such as antacids and acid-binding medications.

Step 2:

Get everything you need for your stool sample from your doctor. A spatula for sampling is already integrated in the sterile stool tube. Place the tube in the bathroom so that you have it at hand the next time you go to the restroom. Fresh stool is needed for the examination. Read the description that comes with the stool sample set carefully.

Step 3:

Find a toilet where you’re comfortable. Your stool sample can easily become contaminated from toilet water, urine and paper, so prepare in advance to take the sample without contamination. For this reason, you shouldn’t do the stool sample in a public toilet.

Step 4:

Sampling may not be easy. However, there are special paper hangers to catch the stool. These are also good for inspecting the stool and then taking a suitable sample. If your doctor didn’t provide you with a paper hanger, we have a few helpful tips:

Tip 1: Cling film Build your own using cling film. Lift the toilet seat and stretch enough cling film over the toilet bowl. Then lower the toilet seat again to hold the film in place Press a small hollow into the film that catches the stool. You can also attach the film to the toilet bowl with adhesive tape.

Tip 2: Newspaper No cling film at hand? Then use newspaper. Use a large double page to catch the stool. Clamp the newspaper between the toilet bowl and toilet seat, and you’re ready to go.

Step 5:

Now you can take care of your bowel movement, but be careful not to urinate as it contaminates the sample. It’s best to empty your bladder before you do the stool sample.

How much stool do I need for the sample, and what do I do with it?

Stool sample

You can take fresh stool from three different places using the spatula. The important thing is that you sample the blood or mucus patches.

Quantity

Fill the tube you were given with the stool. About one walnut-sized amount (three milliliters) is sufficient for most examinations. If the tube has a marking, please fill it with stool up to the mark. If an examination for parasites is pending, the tube should be at least a third full. If you have diarrhea, you should at least collect five milliliters of stool.

Packing

Screw the spatula to the tube and put both in the slightly larger transport tube. You're almost done: Now you only have to label the tube with your data and hand it in to your doctor.

Storage

Can't go straight to the doctor? Pack your stool sample in a bag and put it in the fridge. There is one exception here: for microbiological tests, the sample must be kept at body temperature! This includes all examinations carried out if an intestinal infection is suspected. If you are unsure, ask your doctor or the laboratory directly. It is best if the stool sample is not stored for a long time. You should definitely go to the laboratory within 24 hours.

Several stool samples

Do you need several stool samples? Then be sure to do this on different days.

As a rule, three stool samples are necessary if infectious diarrhea is suspected. But don't wait until you have taken the last one before you turn in the first sample! It is important that the first sample is analyzed promptly.

Can the stool sample be sent by post?

It is common in many places for the stool sample to be sent to the laboratory by post. However, this approach is not optimal. Please always hand in the stool sample directly to the staff and do not throw it in the mailbox on weekends or during closing times. The long pickup time can influence the test result.

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Do I need an analysis of my stool if I have diarrhea?

In certain cases, it may be useful to carry out a stool sample if you have diarrhea. The microbiological examination of the stool includes the detection of various bacteria, viruses and fungi, as well as parasites. Since many diarrheal diseases are self-limiting, that is, they get better and disappear on their own, a pathogen diagnosis in the stool sample is not absolutely necessary in the case of diarrhea. With severe symptoms with fever and persistent diarrhea, you should definitely see your family doctor to find out the cause. In particular, if your diarrhea occurs after traveling abroad or in connection with food, we recommend a microbiological analysis of your stool in order to identify the pathogen and initiate appropriate therapy. If you have permanent (chronic) diarrhea, the stool sample can also provide information about the cause of your complaints. The following table gives you an overview of the diseases for which an examination of your stool makes sense.

Illness Examination of stool for
Acute diarrhea - bacteria

- viruses

- fungus

- parasites

(Three samples on different days)

Digestive problems (maldigestion)

- celiac disease (sprue)

- lactase deficiency

- fat excretion

- gliadin antibodies

- transglutaminase antibodies

- bacterial breakdown activity

(fructose, sorbitol, xylitol)

Pancreatic dysfunction - fat excretion

- pancreatic elastase-1 (enzyme)

Histamine intolerance - histamine levels
Suspected gastrointestinal bleeding

- diverticulum

- polyps

- occult blood
Cancer screening

- colorectal cancer

- occult blood

- antigen determination (M2PK)

Examination for occult blood in the stool

Occult comes from Latin and means “hidden.” The examination for occult blood in the stool is used to detect blood that’s not visible to the naked eye. It serves, among other things, for early detection of colon cancer. As of recently, an immunological test (iFOBT) may be used during stool examinations. This is even more sensitive than the previously used hemoccult test. It can detect blood even better in the stool sample.

Colon cancer often leads to symptoms very late (when the disease is already advanced). Therefore, screening for occult blood is very important and regular preventative medical check-ups from the age of 50 years can be of great help.

The stool is also checked for occult blood if bleeding in the digestive tract is suspected. These can arise from polyps or diverticula. In this case, the so-called hemoccult test is currently still being carried out.

Help, my stool test is positive! What does that mean?

First keep calm. If it is a test for occult (hidden) blood, a positive means that blood could be detected in your stool sample. This can have many causes so discuss the result with your doctor, because she knows your symptoms and the reason for the test and can thus better assess the result.

Is your bowel cancer screening positive?

There is no reason to panic. Although blood in the stool can indicate a tumor, there are also a lot of other causes. For example, injuries in the anal area, hemorrhoids, or bleeding in the gastrointestinal tract due to diverticula or polyps may be the cause. In the event of a positive test result, it is very important that you investigate the cause together with your doctor, who will likely advise a colonoscopy.

“Positive” stool examination in a chronic diarrhea diagnosis

If you have had a stool examination because of chronic diarrhea, the word positive can mean different things. In the context of a microbiological test, it means that a pathogen (viruses, bacteria, parasites) was detected. This will be communicated to you, and appropriate treatment will be started. In the table you can see which pathogens cause diarrhea (infectious enteritis).

Base of infectious diarrhea Pathogen
Bacteria - clostridium difficile

- dyspepsia coli

- escherichia coli

- gas-producing bacteria

- salmonella

- shigella

- staphylococci (with enterotoxins)

- v. cholerae

- yersinia Campylobacter

Virus - adenoviruses

- norovirus

- rotaviruses

Fungi Candida
Parasites Microscopic examination:

- amoeba

- lamblia

- worms

- worm eggs

Chronic diarrhea can also have non-infectious causes. Bloody stool can occur with inflammatory bowel diseases such as ulcerative colitis. In this case, too, a stool examination is not sufficient for a diagnosis: A colonoscopy should also be performed.

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Dr. med. Andre Sommer

Dr. med. Andre Sommer

I’m André, a medical doctor from Berlin. Together with a team of medical doctors, nutritionists and data scientists we empower people to understand digestive issues with our app Cara Care.

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