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Fecal fat

Definition

The fecal fat test measures the amount of fat in the stool, which helps estimate the percentage of dietary fat that the body does not absorb.

Alternative Names

Quantitative stool fat determination; Fat absorption

How the test is performed

Adults and children:

There are many ways to collect the samples. 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.

Infants and young children:

For children wearing diapers, you can line the diaper with plastic wrap. If the plastic wrap is positioned properly, you can prevent mixing of urine and stool. Preventing such mixing can give a better sample.

Collect all stool that is released over a 24-hour period (or sometimes 3 days) in special containers. Label the containers with name, time, and date, and send them to the laboratory.

How to prepare for the test

Eat a normal diet containing about 100 grams of fat per day for 3 days before starting the test. The health care provider may ask you to stop using substances that can affect test results, such as drugs or food additives.

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.

Fat malabsorption can cause a change in your stools called steatorrhea. To absorb fat normally, the body needs bile from the gallbladder (or liver if the gallbladder has been removed), enzymes from the pancreas, and normal intestines.

Normal Values

Less than 7 grams of fat per 24 hours.

What abnormal results mean

Decreased fat absorption may be caused by:

• Biliary cancer
• Biliary stricture
• Celiac disease
• Chronic pancreatitis
• Crohn's disease
• Cystic fibrosis
• Gallstones (cholelithiasis)
• Pancreatic cancer
• Pancreatitis
• Radiation enteritis
• Short bowel syndrome (e.g., from surgery or an inherited problem)
• Sprue
• Whipple's disease

What the risks are

There are no risks.

Special considerations

Factors that interfere with the test are:

• Enemas
• Laxatives
• Mineral oil

References

Semrad CE, Powell DW. Approach to the patient with diarrhea and malabsorption. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 143.