Fecal Fat

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Fecal Fat

Synonym/acronym: Stool fat, fecal fat stain.

Common use

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


Stool (80 mL) aliquot from an unpreserved and homogenized 24- to 72-hr timed collection. Random specimens may also be submitted.

Normal findings

(Method: Stain with Sudan black or oil red O. Treatment with ethanol identifies neutral fats; treatment with acetic acid identifies fatty acids.)
Random, Semiquantitative
Neutral fatLess than 60 fat globules/hpf*
Fatty acidsLess than 100 fat globules/hpf
72-hr, Quantitative
Age (normal diet)
 Infant (breast milk)Less than 1 g/24 hr
 0–6 yrLess than 2 g/24 hr
 Adult2–7 g/24 hr; less than 20% of total solids
Adult (fat-free diet)Less than 4 g/24 hr
*hpf = high-power field.


Fecal fat primarily consists of triglycerides (neutral fats), fatty acids, and fatty acid salts. Through microscopic examination, the number and size of fat droplets can be determined as well as the type of fat present. Excretion of more than 7 g of fecal fat in a 24-hr period is abnormal but nonspecific for disease. Increases in excretion of neutral fats are associated with pancreatic exocrine insufficiency, whereas decreases are related to small bowel disease. An increase in triglycerides indicates that insufficient pancreatic enzymes are available to convert the triglycerides into fatty acids. Patients with malabsorption conditions have normal amounts of triglycerides but an increase in total fecal fat because the fats are not absorbed through the intestine. Malabsorption disorders (e.g., cystic fibrosis) cause blockage of the pancreatic ducts by mucus, which prevents the enzymes from reaching the duodenum and results in lack of fat digestion. Without digestion, the fats cannot be absorbed, and steatorrhea results. The appearance and odor of stool from patients with steatorrhea is typically foamy, greasy, soft, and foul-smelling. The semiquantitative test is used to screen for the presence of fecal fat. The quantitative method, which requires a 72-hr stool collection, measures the amount of fat present in grams.

This procedure is contraindicated for



  • Assist in the diagnosis of malabsorption or pancreatic insufficiency, as indicated by elevated fat levels
  • Monitor the effectiveness of therapy

Potential diagnosis

Increased in

  • Abetalipoprotein deficiency (related to lack of transport proteins for absorption)
  • Addison’s disease (related to impaired transport)
  • Amyloidosis (increased rate of excretion related to malabsorption)
  • Bile salt deficiency (related to lack of bile salts required for proper fat digestion)
  • Carcinoid syndrome (increased rate of excretion related to malabsorption)
  • Celiac disease (increased rate of excretion related to malabsorption)
  • Crohn’s disease (increased rate of excretion related to malabsorption)
  • Cystic fibrosis (related to insufficient digestive enzymes)
  • Diabetes (abnormal motility related to primary condition)
  • Enteritis (increased rate of excretion related to malabsorption)
  • Malnutrition (related to detrimental effects on organs and systems responsible for digestion, transport, and absorption)
  • Multiple sclerosis (abnormal motility related to primary condition)
  • Pancreatic insufficiency or obstruction (related to insufficient digestive enzymes)
  • Peptic ulcer disease (related to improper digestion due to low pH)
  • Pernicious anemia (related to bacterial overgrowth that decreases overall absorption and results in vitamin B12 deficiency)
  • Progressive systemic sclerosis (abnormal motility related to primary condition)
  • Thyrotoxicosis (abnormal motility related to primary condition)
  • Tropical sprue (increased rate of excretion related to malabsorption)
  • Viral hepatitis (related to insufficient production of digestive enzymes and bile)
  • Whipple’s disease (increased rate of excretion related to malabsorption)
  • Zollinger-Ellison syndrome (related to improper digestion due to low pH)

Decreased in


Critical findings


Interfering factors

  • Cimetidine has been associated with decreased fecal fat in some patients with cystic fibrosis who are also receiving pancreatic enzyme therapy.
  • Some drugs cause steatorrhea as a result of mucosal damage. These include colchicine, kanamycin, lincomycin, methotrexate, and neomycin. Other drugs that can cause an increase in fecal fat include aminosalicylic acid, bisacodyl and phenolphthalein (observed in laxative abusers), and cholestyramine (in high doses).
  • Use of suppositories, oily lubricants, or mineral oil in the perianal area for 3 days before the test can falsely increase neutral fats.
  • Use of herbals with laxative effects, including cascara, psyllium, and senna, for 3 days before the test can falsely increase neutral fats.
  • Barium interferes with test results.
  • Failure to collect all stools may reflect falsely decreased results.
  • Ingestion of a diet too high or low in fats may alter the results.

Nursing Implications and Procedure


  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching:   Inform the patient this test can assist in the diagnosis of intestinal disorders.
  • Obtain a history of the patient’s complaints that indicate a gastrointestinal (GI) disorder, diarrhea related to GI dysfunction, pain related to tissue inflammation or irritation, alteration in diet resulting from an inability to digest certain foods, or fluid volume deficit related to active loss. Obtain a history of known allergens.
  • Obtain a history of the patient’s gastrointestinal and respiratory systems, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Note any recent procedures that can interfere with test results.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values).
  • Review the procedure with the patient. Stress the importance of collecting all stools for the quantitative test, including diarrhea, over the timed specimen-collection period. Inform the patient not to urinate in the stool-collection container and not to put toilet paper in the container. Address concerns about pain related to the procedure. Explain to the patient that there should be no discomfort during the procedure.
  • Sensitivity to social and cultural issues,  as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Instruct the patient not to use laxatives, enemas, or suppositories for 3 days before the test.
  • Note that there are no fluid 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.


  • Potential complications: N/A
  • Ensure that the patient has complied with dietary and other pretesting preparations prior to the procedure.
  • Instruct the patient to cooperate fully and to follow directions.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and the start and stop times of collection.
  • Obtain the appropriate-sized specimen container, toilet-mounted collection container to aid in specimen collection, and plastic bag for specimen transport. 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.
  • For the quantitative procedure, instruct the patient to collect each stool and place it in the 500-mL container during the timed collection period. Keep the container refrigerated in the plastic bag throughout the entire collection period.
  • Promptly transport the specimen to the laboratory for processing and analysis.


  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Instruct the patient to resume usual diet and medication, as directed by the HCP.
  • Recognize anxiety related to test results, and be supportive of impaired activity related to perceived loss of independence and fear of shortened life expectancy. Discuss the implications of abnormal test results on the patient’s lifestyle. Instruct the patient with abnormal values on the importance of fluid intake and proper diet specific to his or her condition. Provide teaching and information regarding the clinical implications of the test results, as appropriate. Educate the patient regarding access to counseling services. Help the patient and caregiver cope with long-term implications. Recognize that anticipatory anxiety and grief may be expressed when someone is faced with a chronic disorder. Provide contact information, if desired and as appropriate, for the American Diabetes Association (www.diabetes.org), the Celiac Disease Foundation (www.celiac.org), the Crohn’s and Colitis Foundation of America (www.ccfa.org), or the Cystic Fibrosis Foundation (www.cff.org).
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include α1-antitrypsin/phenotyping, biopsy intestine, chloride sweat, CBC, CBC RBC indices, CBC RBC morphology, d-xylose tolerance test, fecal analysis, folate, gastric acid stimulation test, gastric emptying scan, radioactive iodine uptake, and vitamin B12.
  • Refer to the Gastrointestinal and Respiratory systems tables at the end of the book for related tests by body system.
Handbook of Laboratory and Diagnostic Tests, © 2013 Farlex and Partners