fecal fat (Fat absorption, Quantitative stool fat determination)
المؤلف:
Kathleen Deska Pagana, Timothy J. Pagana, Theresa Noel Pagana.
المصدر:
Mosbys diagnostic and laboratory test reference
الجزء والصفحة:
15th edition , p406-407
2025-12-13
56
Type of test Stool
Normal findings
Fat: 2-6 g/24 hr or 7-21 mmol/day (SI units)
Retention coefficient: ≥ 95%
Test explanation and related physiology
This qualitative or quantitative test is performed to confirm the diagnosis of steatorrhea. Steatorrhea occurs when fat con tent in the stool is high. It is suspected when the patient has large, greasy, and foul-smelling stools. Determining an abnormally high fecal fat content confirms the diagnosis. Short-gut syndrome and any condition that may cause malabsorption (e.g., sprue, Crohn disease, Whipple disease) or maldigestion (e.g., bile duct obstruction, pancreatic duct obstruction secondary to tumor or gallstones) are also associated with increased fecal fat.
The total output of fecal fat can be tested on a random stool specimen but is more accurate when total 24-, 48-, or 72-hour collection is carried out. Abnormal results from a random specimen should be confirmed by submission of a timed collection. Test values for random fecal fat collections are reported in terms of percent fat.
Interfering factors
* Drugs that may alter test results include enemas and laxatives, especially mineral oil.
* Drugs that may decrease levels of fecal fat include barium and psyllium fiber (e.g., Metamucil).
Procedure and patient care
Before
* Explain the procedure to the patient.
* Instruct the patient to abstain from alcohol ingestion for 3 days before testing.
* Give the patient instructions regarding the appropriate diet (a diet diary may be requested by the laboratory):
• For adults, usually 100 g of fat per day is suggested for 3 days before and during the collection period.
• Children, and especially infants, cannot ingest 100 g of fat. Therefore a fat retention coefficient is determined by measuring the difference between ingested fat and fecal fat and then expressing that difference (the amount of fat retained) as a percentage of the ingested fat:
• Note that the normal fat retention coefficient is 95% or greater. A low value indicates steatorrhea.
• For qualitative analysis, the stool is microscopically examined for fat globules. Instruct the patient to defecate in a dry, clean container.
• Occasionally, a tongue blade is required to transfer the stool to the specimen container.
* Tell the patient not to urinate in the stool container.
* Inform the patient to collect diarrheal stools.
* Instruct the patient that toilet paper should not be placed in the stool container.
* Tell the patient not to take any laxatives or enemas during this test because they will interfere with intestinal motility and alter test results.
During
• Collect each stool specimen and send immediately to the lab oratory during the 24- to 72-hour testing period. Label each specimen and include the time and date of collection.
• If the specimen is collected at home, give the patient a large stool container to keep in the freezer.
After
• Inform the patient that a normal diet can be resumed.
Abnormal findings
Increased levels
- Cystic fibrosis
- Malabsorption secondary to sprue, celiac disease, Whipple disease, Crohn disease, or radiation enteritis
- Maldigestion secondary to obstruction of the pancreatico biliary tree (e.g., cancer, stricture, gallstones)
- Short-gut syndrome secondary to surgical resection, surgical bypass, or congenital anomaly
الاكثر قراءة في التحليلات المرضية
اخر الاخبار
اخبار العتبة العباسية المقدسة
