Fecal fat, quantification
Fecal fat, stool
Random: < 60 droplets of fat/high power field
72-hour: < 7 g/day
Qualitative: Random stool sample is adequate.
Quantitative: Dietary fat should be about 100 g/day for 5 days before and during stool collection. Then all stools should be collected for 72 hrs and refrigerated.
In healthy people, most dietary fat is completely absorbed in the small intestine. Normal small intestinal lining, bile acids, and pancreatic enzymes are required for normal fat absorption.
Increased in: Malabsorption from small bowel disease (regional enteritis, celiac disease (gluten enteropathy), tropical sprue), pancreatic insufficiency, diarrhea with or without fat malabsorption.
72-hr fecal fat quantification is considered the gold standard for the diagnosis of pancreatic exocrine insufficiency. However, the test is cumbersome and unpleasant for patient and testing personnel. Test not routinely available.
A random, qualitative fecal fat (so-called Sudan stain) is useful only if positive. Furthermore, it does not correlate well with quantitative measurements. Sudan stain appears to detect triglycerides and lipolytic by-products, whereas 72-hour fecal fat measures fatty acids from a variety of sources, including phospholipids, cholesteryl esters, and triglycerides.
The quantitative method can be used to measure the degree of fat malabsorption initially and then after a therapeutic intervention.
A normal quantitative stool fat reliably rules out pancreatic insufficiency and most forms of generalized small intestine disease.
Besides fecal fat quantification, fecal pancreatic elastase 1 can be used to evaluate pancreatic insufficiency with excellent sensitivity. The13C-mixed triglycerides breath test has also been introduced and adopted by many laboratories.
Domínguez-Muñoz JE. Pancreatic exocrine insufficiency: diagnosis and treatment. J Gastroenterol Hepatol. 2011;26:S12. [PMID: 21323992]
Lindkvist B. Diagnosis and treatment of pancreatic exocrine insufficiency. World J Gastroenterol 2013;19:7258. [PMID: 24259956]