Malabsorption laboratory findings
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Malabsorption |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2]
Overview
Laboratory Findings
There is no specific test for malabsorption. As for most medical conditions, investigation is guided by symptoms and signs. Moreover, tests for pancreatic function are complex and varies widely between centers.
Blood Tests
- Routine blood tests may reveal anaemia, high ESR or low albumin; which has high sensitivity for presence of organic disease.[1][2] In this setting, microcytic anaemia usually implies iron deficiency and macrocytosis can be from impaired folic acid or B12 absorption or both. Low cholesterol or triglyceride may give clue toward fat malabsorption as low calcium and phosphate toward osteomalacia from low vitamin D.
- Specific vitamins like vitamin D or micro nutrient like zinc levels can be checked. Fat soluble vitamins (A, D, E and K) are affected in fat malabsorption. Prolonged prothrombin time can be from vitamin K deficiency.
- Serological studies:
- Specific tests are carried out to determine underlying cause.
- IgA tissue trans glutamate or IgA antiendomysium assay for gluten sensitive enteropathy.
Stool Studies
- Microscopy is particularly useful in diarrhea, may show protozoa like giardia, ova, cyst and other infective agents.
- Fecal fat study to diagnose steatorrhea is less frequently performed nowadays.
- Low elastase is indicative of pancreatic insufficiency. Chymotrypsin and pancreolauryl can be assessed as well.[3]
Approach to a Patient with Malabsorption
| Clinical suspicion of malabsorption syndrome | |||||||||||||||||||||||||||||||||||||||||||||||
| Initial screening perform: •Stool microscopy to rule out infectious causes •D-xylose test to test for the presence of intestinal enterocyte dysfunction •Fecal fat test for detection of steatorrhea | |||||||||||||||||||||||||||||||||||||||||||||||
| If D-Xylose and feacal fat tests are positive, confirmatory tests for malabsoption should be done | |||||||||||||||||||||||||||||||||||||||||||||||
| •Positive antiendomysial antibodies and villous atrophy suggests celiac disease •Positive breath hydrogen test suggests lactase deficiency •Positive microscopy and culture of jejunal aspirate suggests small bowel bacterial overgrowth •Low serum immunoglobulin suggests B-cell deficiency •HIV serology for HIV infection •CT enterography to rule out intestinal inflammatory conditions •Abdomen CT to rule out chronic pancreatitis | |||||||||||||||||||||||||||||||||||||||||||||||
| Once other possibilities are ruled out, suspect diagnosis of tropical sprue | |||||||||||||||||||||||||||||||||||||||||||||||
| Start tetracycline therapy Improvement of symptoms with tetracycline confirms the diagnosis | |||||||||||||||||||||||||||||||||||||||||||||||
References
- ↑ Bertomeu A, Ros E, Barragán V, Sachje L, Navarro S (1991). "Chronic diarrhea with normal stool and colonic examinations: organic or functional?". J. Clin. Gastroenterol. 13 (5): 531–6. PMID 1744388.
- ↑ Read N, Krejs G, Read M, Santa Ana C, Morawski S, Fordtran J (1980). "Chronic diarrhea of unknown origin". Gastroenterology. 78 (2): 264–71. PMID 7350049.
- ↑ Thomas P, Forbes A, Green J, Howdle P, Long R, Playford R, Sheridan M, Stevens R, Valori R, Walters J, Addison G, Hill P, Brydon G (2003). "Guidelines for the investigation of chronic diarrhoea, 2nd edition". Gut. 52 Suppl 5: v1–15. PMID 12801941.[1].