Fecal fat

In medicine, a fecal fat test is a diagnostic test for fatmalabsorptionconditions (also referred to as steatorrhea).

Background

In the small intestine, dietary fat (primarily triglycerides) is digested by enzymessuch as pancreatic lipaseinto smaller molecules which can be absorbed through the wall of the small intestine and enter the circulationfor metabolismand storage. As fatis a valuable nutrient, human fecesnormally contain very little undigested fat. However, a number of diseases of the pancreas and gastrointestinal tract are characterized by fat malabsorption.

Examples of such diseases are:

• disorders of exocrine pancreaticfunction, such as cystic fibrosisand Schwachman syndrome(both characterized by deficiency of pancreatic digestive enzymes)
• celiac disease(in which the fat malabsorption in severe cases due to inflammatory damage to the integrity of the intestinal lining)
• short gut syndrome(in which much of the small intestine has had to be surgically removed and the remaining portion cannot completely absorb all of the fat).

Microscopy

In the simplest form of the fecal fat test, a random fecal specimen is submitted to the hospital laboratoryand examined under a microscopeafter stainingwith a Sudan IIIor Sudan IVdye ("Sudan staining"). Visible amounts of fat indicate some degree of fat malabsorption.

Quantitative fecal fat test

Quantitative fecal fat tests measure and report an amount of fat. This usually done over a period of three days, the patient collecting all of their feces into a container. This is generally an unpleasant experience for both patient and staff.

The container is thoroughly mixed to homogenize the feces, this can be done with a paint mixer. A small sample from the feces is collected. The fat content is extracted with solventsand measured by saponification(turning the fat into soap).

Normally up to 7 gramsof fat can be malabsorbed in people consuming 100 grams of fat per day. In patients with diarrhea, up to 12 grams of fat may be malabsorbed since the presence of diarrhea interferes with fat absorption, even when the diarrhea is not due to fat malabsorption.

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Fecal+fat Wikipedia article Fecal fat.