The fecal fat test measures the amount of fat in the stool. This can help gauge the percentage of dietary fat that the body does not absorb.
Quantitative stool fat determination; Fat absorption
How the Test is Performed
There are many ways to collect the samples.
- For adults and children, you can catch the stool on plastic wrap that is loosely placed over the toilet bowl and held in place by the toilet seat. Then put the sample in a clean container. One test kit supplies a special toilet tissue that you use to collect the sample, then put the sample in a clean container.
- For infants and children wearing diapers, you can line the diaper with plastic wrap. If the plastic wrap is placed properly, you can prevent mixing of urine and stool. This will provide a better sample.
Collect all stool that is released over a 24-hour period (or sometimes 3 days) in the containers provided. Label the containers with name, time, and date, and send them to the lab.
How to Prepare for the Test
Eat a normal diet containing about 100 grams (g) of fat per day for 3 days before starting the test. The health care provider may ask you to stop using drugs or
How the Test will Feel
The test involves only normal bowel movements. There is no discomfort.
Why the Test is Performed
This test evaluates fat absorption to tell how well the liver, gallbladder, pancreas, and intestines are working.
Less than 7 g of fat per 24 hours.
What Abnormal Results Mean
Decreased fat absorption may be caused by:
tumor Biliary stricture Celiac disease(sprue) Chronic pancreatitis Crohn disease Cystic fibrosis
- Gallstones (
cholelithiasis) Pancreatic cancer
Radiation enteritis Short bowel syndrome(for example from surgery or an inherited problem)
- Small bowel bacterial overgrowth
There are no risks.
Factors that interfere with the test are:
- Mineral oil
- Inadequate fat in diet prior to and during the stool collection
Huston CD. Intestinal protozoa. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 113.
Semrad CE. Approach to the patient with diarrhea and malabsorption. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 131.
Siddiqui UD, Hawes RH. Chronic pancreatitis. In: Chandrasekhara V, Elmunzer JB, Khashab MA, Muthusamy RV, eds. Clinical Gastrointestinal Endoscopy. 3rd ed. Philadelphia, PA: Elsevier; 2019:chap 59.
Review Date: 07/30/2022
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