Drummey et al developed a method for screening random stool specimens for fecal fat in order to identify patients with steatorrhea. This can be used to identify patients who might benefit from a quantitative fat analysis or to monitor patients over time.
Method:
(1) A small amount of representative stool is collected.
(2) For examination of neutral fat:
(2a) A small amount of stool is mixed with 2 drops of water.
(2b) 2 drops of 95% ethanol are added and mixed.
(2c) A few drops of saturated Sudan III in 95% ethanol is then added and mixed.
(2d) A coverslip is then placed and the slide examined.
(3) For examination of split fats (free fatty acids):
(3a) A small amount of stool is mixed with 2 drops of water.
(3b) Several drops of 36% acetic acid are added and mixed.
(3c) A few drops of saturated Sudan III in 95% ethanol is then added and mixed.
(3d) The slide is heated over low heat until the mixture starts to boil, and then it is cooled.
(3e) The heating and cooling steps are quickly repeated 2-3 times.
(3f) A coverslip is then placed and the slide examined.
(4) The slide is examined at high dry power (magnification x430) using a micrometer scale.
(4a) Neutral fat will appear as yellow or pale-orange refractile globules in the first preparation.
(4b) Free fatty acid droplets are deep-orange that are globules when the slide is warm and which appear as spicules or soap forms when the slide cools.
Neutral fat globules are normally absent or rare. A large amount of neutral fat may occur with:
(1) administration of mineral or castor oil
(2) some low-calorie foods from nonabsorbed oil
(3) pancreatic insufficiency
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Size of Free Fatty Acid Droplets
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Number of Free Fatty Acid Droplets per High Power Field
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Fecal Material
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Estimate
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1 – 4 microns
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< 100
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much
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normal (+)
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1 – 8 microns
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>= 100
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reduced
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slight increase (++)
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6 – 75 microns present
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>= 100
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none
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definite increase (+++)
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where:
• 8 microns is about the size of red blood cell
• There would seem to be need for a level between ++ and +++, for which the number of larger fat droplets would be < 100.
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Percent of Fat Intake in Feces
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normal (+)
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slight increase (++)
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definite increase (+++)
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0 – 5% (normal)
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86%
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14%
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0
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6 – 10%
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12.5%
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12.5%
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75%
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11 – 15%
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0
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6%
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94%
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> 15%
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0
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0
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100%
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after Table 1, Drummey (1961)
Performance:
• The test is mainly of historic interest. However, it may still be of use if resources are limited.
