section name header

Introduction ⬇

Fecal fat is the gold standard test for diagnosing steatorrhea (malabsorption). The three major causes of steatorrhea, which is a pathologic increase in fecal fat, are impairment of intestinal absorption, deficiency of pancreatic digestive enzymes, and deficiency of bile.

Specimens from patients suspected of having steatorrhea can be screened microscopically for the presence of excess fecal fat. This procedure can also be used to monitor patients undergoing treatment for malabsorption disorders. In general, there is good correlation between the qualitative and quantitative fecal fat procedures. Lipids included in the microscopic examination of feces are neutral fats (triglycerides), fatty acid salts (soaps), fatty acids, and cholesterol. The presence of these lipids can be observed microscopically by staining with Sudan III, Sudan IV, or Oil Red O dye. The staining procedure consists of two parts: the neutral fat stain and the split fat stain for fatty acids.

Normal Findings ⬆ ⬇

  1. Qualitative

    1. Neutral fat: less than 60 fat globules per high-power field

    2. Fatty acids: less than 100 fat globules per high-power field

  2. Quantitative

    1. Adult: 2–7 g/24 hr or 2–7 g/d and less than 20% of total solids

    2. Child: less than 2.0 g/24 hr or less than 2.0 g/d

    3. Infant: less than 1.0 g/24 hr or less than 1.0 g/d and breast-fed 10% to 40% of total solids; bottle-fed 30%–50% of total solids

    4. Coefficient of fat absorption (%) = (fat ingested − fat excreted)/fat ingested × 100

Procedure ⬆ ⬇

  1. Collect a 48- to 96-hour specimen following the procedure for Collection and Transport of 24-, 48-, 72-, and 96-Hour Stool Specimens for the quantitative test. Observe standard precautions. 
A random specimen can be used for the qualitative test. Label each individual stool specimen with the patient’s name, date and time of collection, and test(s) ordered. Also indicate the length (actual time frame) of the collection period. The specimen should be sent immediately to the laboratory.

  2. Follow the procedure for the collection of 24-, 48-, or 72-hour specimens.

Clinical Implications ⬆ ⬇

  1. Increases in fecal fat and fatty acids are associated with malabsorption syndrome caused by the following conditions:

    1. Celiac disease

    2. Crohn disease

    3. Whipple disease (systemic infectious disease caused by Tropheryma whipplei)

    4. Cystic fibrosis

    5. Regional enteritis

    6. Atrophy of malnutrition

  2. Increases in fecal fat and fatty acids are also found in the following conditions:

    1. Enteritis and pancreatic diseases in which there is a lack of lipase (e.g., chronic pancreatitis)

    2. Surgical removal of a section of the intestine

  3. Fecal fat test does not provide a diagnostic explanation for the presence of steatorrhea. It is not useful for differentiating among pancreatic diseases.

    1. D-Xylose absorption test may be ordered for the differential diagnosis of malabsorption.

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain purpose of test, procedure for stool collection, and interfering factors.

  2. For a 72- to 96-hour stool collection, ensure the patient follows a diet containing 100–150 g of fat, 100 g of protein, and 180 g of carbohydrate for 6 days before and during the test. Fat substitutes or fat-blocking nutritional supplements should be eliminated.

  3. Advise the patient to avoid laxatives for 3 days before stool specimen collection.

  4. Follow the procedure for the collection of 72-hour stool specimens.

  5. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Have the patient resume a normal diet after testing is complete.

  2. Report and record appearance, color, and odor of all stools in persons suspected of having steatorrhea. The typical stool in patients with this condition is foamy, greasy, soft, pasty, and foul smelling. Modify the nursing care plan as needed.

  3. Counsel the patient regarding abnormal findings; explain the possible need for further testing (e.g., colonoscopy) and treatment (e.g., elimination of certain foods from the diet).

  4. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Interfering Factors ⬆

  1. Increased neutral fat may occur under the following nondisease conditions:

    1. Use of rectal suppositories or oily creams applied to the perineum

    2. Ingestion of castor oil, mineral oil

    3. Ingestion of dietetic low-calorie mayonnaise, oily salad dressings

    4. Ingestion of high-fiber diet (more than 100 g/24 hr or more than 100 g/d)

    5. Use of psyllium-based stool softeners (e.g., Metamucil)

  2. Use of barium and bismuth interferes with test results.

  3. Urine contaminates the specimen.

  4. A random stool specimen is not an acceptable sample for the quantitative fat test.