Stool analysis

A stool analysis is a series of tests done on a sample of stool (feces). It can find problems with the digestive tract. These health problems can include infection, poor nutrient absorption, or cancer.

Stool analysis is done to:

• Help identify diseases of the digestive tract, liver, and pancreas. Certain enzymes (such as trypsin or elastase) may be evaluated in the stool to help see how well the pancreas is working.
• Help find the cause of symptoms affecting the digestive tract, such as prolonged diarrhea, bloody diarrhea, an increased amount of gas, nausea, vomiting, loss of appetite, bloating, belly pain and cramping, and fever.
• Screen for colon cancer by checking for hidden (occult) blood.
• Look for parasites, such as pinworms or Giardia.
• Look for the cause of an infection, such as bacteria, a fungus, or a virus.
• Check for poor absorption of nutrients by the digestive tract (malabsorption syndrome). For this test, all stool is collected over a 72-hour period and then checked for fat (and sometimes for meat fibers). This test is called a 72-hour stool collection or quantitative fecal fat test.

You will be given stool collection kits to use each day. You may need to collect more than one sample. Follow the directions in the kits. The contents may be different.

• Urinate before you collect stool so you don't get any urine in the stool sample.
• Follow the directions for putting the sample collection container on the toilet.
• Pass stool (have a bowel movement) into the collection container.
• Use the stick to take a sample of the stool and place it in the bottle.
• Place the lid on the bottle. Label it with your name and the date the stool was collected.
• Flush the remaining stool down the toilet.
• Seal the collection container in a bag and throw it away.
• Wash your hands.

Your doctor will tell you when to return the sample to the lab.

Many medicines can change the results of this test. You will need to avoid certain medicines depending on which kind of stool analysis you have. You may need to stop taking medicines such as antacids, antidiarrheal medicines, antiparasite medicines, antibiotics, laxatives, or nonsteroidal anti-inflammatory drugs (NSAIDs) for 1 to 2 weeks before you have the test. Be sure to tell your doctor about all the nonprescription and prescription medicines you take.

Be sure to tell your doctor if you have:

• Recently had an X-ray test using barium contrast material, such as a barium enema or upper gastrointestinal series (barium swallow). Barium can interfere with test results.
• Traveled in recent weeks or months, especially if you have traveled outside the country. This helps your doctor look for the parasites, fungi, viruses, or bacteria that may be causing a problem.

If your stool is being tested for blood, you may need to avoid certain foods for 2 to 3 days before the test. This depends on what kind of stool test you use. And do not do the test during your menstrual period or if you have active bleeding from hemorrhoids. If you aren't sure about how to prepare, ask your doctor.

Do not use a stool sample for testing that has been in contact with toilet bowl cleaning products that turn the water blue.

Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.

A stool analysis may check values for pH, reducing factors, and fat.

Many conditions can change the results of a stool analysis. Your doctor will talk with you about any abnormal results that may be related to your symptoms and past health.

Abnormal values

• High levels of fat in the stool may be caused by diseases such as pancreatitis, sprue (celiac disease), cystic fibrosis, or other disorders that affect the absorption of fats.
• The presence of undigested meat fibers in the stool may be caused by pancreatitis.
• A low pH may be caused by poor absorption of carbohydrate or fat. Stool with a high pH may mean inflammation in the intestine (colitis), cancer, or antibiotic use.
• Blood in the stool may be caused by bleeding in the digestive tract.
• White blood cells in the stool may be caused by inflammation of the intestines, such as ulcerative colitis, or a bacterial infection.
• Rotaviruses are a common cause of diarrhea in young children. If diarrhea is present, testing may be done to look for rotaviruses in the stool.
• High levels of reducing factors in the stool may mean a problem digesting some sugars.
• Low levels of reducing factors may be caused by sprue (celiac disease), cystic fibrosis, or malnutrition. Medicine such as colchicine (for gout) or birth control pills may also cause low levels.