Fecal Fat


Stool fat, fecal fat stain.

To assess for the presence of fat in the stool toward diagnosing malabsorption disorders such as Crohn disease and cystic fibrosis.

Patient Preparation
There are no fluid or activity restrictions unless by medical direction. Instruct the patient to ingest a diet containing 50 to 150 g of fat for at least 3 days before beginning specimen collection. This approach does not work well with children; instruct the caregiver to record the child’s dietary intake to provide a basis from which an estimate of fat intake can be made. Instruct the patient not to use laxatives, enemas, or suppositories for 3 days before the test. As appropriate, provide the required stool collection container, plastic bag to store container in refrigerator during the collection period, and specimen collection instructions; the test may require either a random specimen or a 72-hr collection. A large, clean, preweighed container should be used for the timed test. A smaller, clean container can be used for the collection of the random sample. Ensure specimen collection for this study is accomplished before any barium procedures are performed.

Normal Findings
Method: Stain with Sudan black or oil red O for qualitative evaluation; nuclear magnetic resonance spectroscopy for quantitative evaluation. Treatment with ethanol identifies neutral fats; treatment with acetic acid identifies fatty acids.

AgeRandom, Qualitative
All Ages0%–19%
24-hr, 48-hr, 72-hr, Quantitative
Age (normal diet)
  Infant (breast milk)Less than 1 g/24 hr
  0–6 yrLess than 2 g/24 hr
  AdultLess than 7 g/24 hr; less than 20% of total solids
Adult (fat-free diet)Less than 4 g/24 hr
*hpf = high-power field.

Critical Findings and Potential Interventions

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