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Malabsorption

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Title: Malabsorption  
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Malabsorption

Malabsorption
Classification and external resources
Whipple's disease: Alcian blue with apparently eosin counterstain enlarged villus with many macrophages
ICD-10 (K90)
ICD-9 579
DiseasesDB 7698
MedlinePlus 000299
eMedicine med/1384
MeSH D008286

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]

Contents

  • Classification 1
  • Pathophysiology 2
  • Causes 3
  • Clinical features 4
  • Diagnosis 5
    • Blood tests 5.1
    • Stool studies 5.2
    • Radiological studies 5.3
    • Interventional studies 5.4
    • Other investigations 5.5
    • Obsolete tests no longer used clinically 5.6
  • Management 6
  • See also 7
  • References 8
  • External links 9

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.
(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 surgical structural changes
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

Small intestine : major site of absorption

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.

Diagnosis

There is no single, 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 centers 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. Tests are also needed to detect the systemic effects of deficiency of the malabsorbed nutrients (such as anaemia with vitamin B12 malabsorption).

Blood tests

  • Routine [9] from low vitamin D.osteomalacia Low calcium and phosphate may give a clue toward [9] absorption or both. Low cholesterol or triglyceride may give a clue toward fat malabsorption.B12 or folic acid can be caused by impaired macrocytosis usually implies iron deficiency and microcytic anaemia In this setting, [8][7]
  • Specific vitamins like vitamin D or micro nutrient like zinc levels can be checked. Fat soluble vitamins (A, D, E & K) are affected in fat malabsorption. Prolonged prothrombin time can be caused by vitamin K deficiency.
  • Serological studies. 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

Biopsy of small bowel showing coeliac disease manifested by blunting of villi, crypt hyperplasia, and lymphocyte infiltration of crypts.

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

References

  1. ^ Jensen, Jonathan E. "Malabsorption Syndromes - Page 1". Colorado center for digestive disorders. Archived from the original on 2007-04-11. Retrieved 2007-05-10. 
  2. ^ 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.  
  3. ^ a b c Bai J (1998). "Malabsorption syndromes". Digestion 59 (5): 530–46.  
  4. ^ 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.  
  5. ^ M. S Losowsky, (1974). Malabsorption in clinical practice. Edinburgh: Churchill Livingstone.  
  6. ^ health a to z"Malabsorption syndrome". Retrieved 2007-05-10. 
  7. ^ 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.  
  8. ^ Read N, Krejs G, Read M, Santa Ana C, Morawski S, Fordtran J (1980). "Chronic diarrhea of unknown origin". Gastroenterology 78 (2): 264–71.  
  9. ^ a b c 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.  [1].

External links

  • Practice guideline from World Gastroenterology Organisation
  • Tests for malabsorption; from British Society for Gastroenterology
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