Quantitative stool fat determination

Alternative names
Fecal fat; Fat absorption

A test that measures the amount of fat in the stool and the percentage of dietary fat that is unabsorbed.

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, isolating the stool from any urine output, mixing of urine and stool can be prevented for a better sample.

Collect all stool excreted over a period of 24-hours (or sometimes 3 days) in special containers, label (name, time, and date), and send them to the laboratory.

How to prepare for the test
Consume a normal diet with about 100 grams of fat per day for 3 days before starting the test. The health care provider may advise you to discontinue use of substances that can affect test results, for example, drugs or food additives.

How the test will feel
The test involves only normal defecation, and there is no discomfort.

Why the test is performed
This test is used to evaluate fat absorption as an indication of liver, gallbladder, pancreas, and intestinal functions.

Lipid (fat) malabsorption is called steatorrhea. Normal lipid absorption requires bile from the gallbladder (or liver if the gallbladder has been removed), enzymes from the pancreas, and a normal intestines.

Normal Values
Less than 7g of fat per 24-hours

What abnormal results mean
Decreased fat absorption may result from:

  • biliary cancer  
  • biliary stricture  
  • celiac disease  
  • cholelithiasis  
  • chronic pancreatitis  
  • Crohn’s disease  
  • cystic fibrosis  
  • pancreatic cancer  
  • pancreatitis  
  • radiation enteritis  
  • short bowel syndrome (e.g., from surgery or congenital anomaly)  
  • sprue  
  • Whipple’s disease

What the risks are
There are no risks.

Special considerations
Interfering factors:

  • enemas  
  • laxatives  
  • mineral oil

Johns Hopkins patient information

Last revised: December 4, 2012
by Janet G. Derge, M.D.

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