Qualitative and quantitative analysis of faecal samples for fat content are useful tests to confirm the presence of fat malabsorption.
Perform 24-48 hours after consumption of approximately 8-9% fat diet. Repeat the test twice.
Test fresh stools.
- Direct test - measures undigested triglycerides. Mix one drop of Sudan III or IV with a drop of fresh faeces on a slide and examine microscopically under a coverslip (x10 magnification). Undigested fat appears as large red-orange coloured globules.
Normal dogs : >3 droplets/ low power field.
- Indirect test - measures "split" fats e.g. fatty acids. Add 2-3 drops of 36% glacial acetic acid to the edge of the coverslip after performing the Direct test (above). Once mixed with the stained faeces, gently warm the slide until it bubbles, then examine whilst still warm. Free fatty acids form droplets large enough to see.
Normal dogs : > 3 droplets/low power field.
In malabsorption there is usually a positive Indirect test and a positive Direct test.
In one study in dogs with exocrine pancreatic insufficiency excessive faecal fat was detected in 86% of cases, whereas only 43% of the dogs had obvious steatorrhoea when the faeces were examined visually.
This test is the most accurate for fat malabsorption and is sensitive for small intestine disease.
A standard diet is fed for 72 hours. All faeces is collected over a 72 hour period and refrigerated. A representative sample is taken and analysed for % fat using the van de Kramer technique.
Normal dogs : 90-95% fat should be absorbed.
In another study steatorrhoea was defined as more than 0.3g fat/kg faeces/day.
Malabsorption : mean 83% fat was absorbed.
Normal cats : excrete 0.35 +/- 0.23 g fat/kg faeces/day.
Steatorrhoea: more than 3.5g fat/kg
Last updated : October 2013