Malabsorption
Malabsorption is a state arising from abnormality in absorption of food nutrients across the gastrointestinal (GI) tract.
Impairment can be of single or multiple nutrients depending on the abnormality. This may lead to malnutrition and a variety of anaemias.[1]
Classification
Some prefer to classify malabsorption clinically into three basic categories:[2]
- (1) selective, as seen in lactose malabsorption;
- (2) partial, as observed in a-Beta-lipoproteinaemia, and
- (3) total as in coeliac disease.
Pathophysiology
The main purpose of the gastrointestinal tract is to digest and absorb nutrients (fat, carbohydrate, protein, and fiber), micronutrients (vitamins and trace minerals), water, and electrolytes. Digestion involves both mechanical and enzymatic breakdown of food. Mechanical processes include chewing, gastric churning, and the to-and-fro mixing in the small intestine. Enzymatic hydrolysis is initiated by intraluminal processes requiring gastric, pancreatic, and biliary secretions. The final products of digestion are absorbed through the intestinal epithelial cells.
Malabsorption constitutes the pathological interference with the normal physiological sequence of digestion (intraluminal process), absorption (mucosal process) and transport (postmucosal events) of nutrients.[3]
Intestinal malabsorption can be due to:[4]
Causes
| Due to infective agents
|
| Due to structural defects[5]
|
| Due to mucosal abnormality
|
Due to enzyme deficiencies
- Lactase deficiency inducing lactose intolerance (constitutional, secondary or rarely congenital)
- Sucrose intolerance
- Intestinal disaccharidase deficiency
- Intestinal enteropeptidase deficiency
|
| Due to digestive failure
|
| Due to other systemic diseases affecting GI tract
|
Clinical features
They can occur in a variety of ways and features might give a clue to the underlying condition. Symptoms can be intestinal or extra-intestinal - the former predominates in severe malabsorption.
- Diarrhoea, often steatorrhoea is the most common feature. Watery, diurnal and nocturnal, bulky, frequent stools are the clinical hallmark of overt malabsorption. It is due to impaired water, carbohydrate and electrolyte absorption or irritation from unabsorbed fatty acid. Latter also results in bloating, flatulence and abdominal discomfort. Cramping pain usually suggests obstructive intestinal segment e.g. in Crohn's disease, especially if it persists after defecation.[3]
- Weight loss can be significant despite increased oral intake of nutrients.[6]
- Growth retardation, failure to thrive, delayed puberty in children
- Swelling or oedema from loss of protein
- Anaemias, commonly from vitamin B12, folic acid and iron deficiency presenting as fatigue and weakness.
- Muscle cramp from decreased vitamin D, calcium absorption. Also lead to osteomalacia and osteoporosis
- Bleeding tendencies from vitamin K and other coagulation factor deficiencies.
Diagnosis
There is no specific test for malabsorption. As for most medical conditions, investigation is guided by symptoms and signs. A range of different conditions can produce malabsorption and it is necessary to look for each of these specifically. Many tests have been advocated, and some, such as tests for pancreatic function are complex, vary between centres and have not been widely adopted. However, better tests have become available with greater ease of use, better sensitivity and specificity for the causative conditions. Test are also needed to detect the systemic effects of deficiency of the malabsorbed nutrients (such as anaemia with vitamin B12 malabsorption).
Blood tests
- Specific tests are carried out to determine the underlying cause.
- IgA Anti-transglutaminase antibodies or IgA Anti-endomysial antibodies for Coeliac disease(gluten sensitive enteropathy).
Stool studies
- Microscopy is particularly useful in diarrhoea, may show protozoa like Giardia, ova, cyst and other infective agents.
- Fecal fat study to diagnose steatorrhoea is rarely performed nowadays.
- Low fecal pancreatic elastase is indicative of pancreatic insufficiency. Chymotrypsin and pancreolauryl can be assessed as well[9]
Radiological studies
Interventional studies
Other investigations
Obsolete tests no longer used clinically
- D-xylose absorption test for mucosal disease or bacterial overgrowth. Normal in pancreatic insufficiency.
- Bile salt breath test (14C-glycocholate) to determine bile salt malabsorption.
- Schilling test to establish cause of B12 deficiency.
Management
Treatment is directed largely towards management of underlying cause:
See also
External links
- Practice guideline from World Gastroenterology Organisation [10]
- Tests for malabsorption; from British Society for Gastroenterology (2003)[11]
References
- ^ Jensen, Jonathan E. "Malabsorption Syndromes - Page 1". Colorado center for digestive disorders. Archived from the original on 2007-04-11. http://web.archive.org/web/20070411100726/http://www.gastromd.com/education/malabsorptionsyndromes.html. Retrieved 2007-05-10.
- ^ Gasbarrini G, Frisono M: Critical evaluation of malabsorption tests; in G. Dobrilla, G. Bertaccini, G. Langman (Editor) (1986). Problems and Controversies in Gastroenterology. New York: Raven Pr. pp. 123–130. ISBN 88-85037-75-5.
- ^ a b c Bai J (1998). "Malabsorption syndromes". Digestion 59 (5): 530–46. doi:10.1159/000007529. PMID 9705537.
- ^ Walker-Smith J, Barnard J, Bhutta Z, Heubi J, Reeves Z, Schmitz J (2002). "Chronic diarrhea and malabsorption (including short gut syndrome): Working Group Report of the First World Congress of Pediatric Gastroenterology, Hepatology, and Nutrition". J. Pediatr. Gastroenterol. Nutr. 35 Suppl 2: S98–105. doi:10.1097/00005176-200208002-00006. PMID 12192177.
- ^ M. S Losowsky, (1974). Malabsorption in clinical practice. Edinburgh: Churchill Livingstone. ISBN 0-443-01007-2.
- ^ health a to z"Malabsorption syndrome". http://www.healthatoz.com/healthatoz/Atoz/common/standard/transform.jsp?requestURI=/healthatoz/Atoz/ency/malabsorption_syndrome.jsp. Retrieved 2007-05-10.
- ^ 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. doi:10.1097/00004836-199110000-00011. 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 (90005): v1–15. doi:10.1136/gut.52.suppl_5.v1. PMC 1867765. PMID 12801941. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1867765. [1].
- ^ http://www.worldgastroenterology.org/malabsorption.html
- ^ http://www.bsg.org.uk/pdf_word_docs/cd_body.pdf