Fecal occult blood
Stool ·Also called: occult blood fecal, hidden blood in stool, FOB test
What it is
The test detects haem, the iron-containing pigment in blood. Bleeding from the stomach or small intestine is digested on its way through and leaves no visible trace, so a chemical test is the only way to find it short of endoscopy.
Why your vet measures it
Slow, hidden gastrointestinal bleeding is a leading cause of iron-deficiency anaemia in dogs, and it can be the first sign of an ulcer or a tumour. Finding it redirects an anaemia investigation towards the digestive tract.
What a positive result can mean
- Bleeding from a stomach or intestinal ulcer, often drug-related
- A gastrointestinal tumour or polyp
- Heavy parasite burden, particularly hookworms
- Severe inflammatory bowel disease
- Meat in the diet, which reacts with the test and causes false positives — a meat-free diet for several days beforehand is usually required
- Swallowed blood from a nosebleed or a mouth wound
What a negative result means
- A negative result makes significant ongoing gastrointestinal bleeding less likely, though bleeding can be intermittent
Questions worth asking your vet
- Was my pet on a meat-free diet for long enough before this test?
- Is my pet on any anti-inflammatory medication that could cause an ulcer?
- Does this warrant looking inside the stomach with a camera?
Related terms
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