Steatorrhea is the passage of fat > 6 g/24 hr stools. Confirmed by repeating the test for 3 consecutive days.
The 1st step after proving steatorrhea is to differentiate between absorptive abnormality and digestive abnormality. This is done by the D-xylose test. D-xylose is a sugar that does not need to be digested (but needs to be absorbed to appear in urine). Hence if urinary excretion is low this infers an absorptive cause for steatorrhea.
Low D-xylose in urine
- Bacterial overgrowth (breath test)
- Celiac disease
- Dermatitis herpetiformis
- Tropical sprue
- Intestinal resection
- Whipple's disease
- Radiation enteritis
- Parasitic infestation (Giardia lamblia)
- Primary lactase deficiency
- Intestinal lymphoma
- Intestinal lymphangiectasia
- Crohn's disease
- Intestinal ischaemia
Bacterial overgrowth is diagnosed by a breath test. Some diseases may require a jejunal biopsy.
Normal D-xylose in urine
1. Pancreatic insufficiency
+ve Benteromide test
- Chronic pancreatitis
- Pancreatic cancer
2. Bile salt deficiency
+ve Bile acid breath test
- Cholestasis (biliary cirrhosis)
- Bacterial overgrowth (deconjugation of bile salts)
- Ilial disease or surgery (decreased reabsorption)
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