Last Updated : 12/30/2010
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Saumil K. Shah
What is digestion and

what is absorption


Digestion means hydrolysis of nutrients. Absorption means uptake of nutrients from the gastrointestinal tract to the systemic circulation.

What is maldigestion


what is malabsorption


Maldigestion denotes impaired nutrient hydrolysis. Malabsorption refers to defective mucosal absorption of nutrients. However, the two entities are so closely linked that in clinical practice malabsorption serves as a global term for all aspects of their impairment. Malabsorption may occur for many nutrients or for specific carbohydrates, fats, or micronutrients.

What steps are involved in digestion and absorption

Three phases are involved:
Luminal phase - Dietary fats, proteins and carbohydrates are hydrolyzed and solubilized, largely by pancreatic and biliary secretions.
Mucosal phase - Terminal hydrolysis of carbohydrate and peptides occurs and fats are processed and ;then packaged for cellular export.
Removal phase - Absorbed nutrients enter the vascular or lymphatic circulation.

Thus defect in any of these phases leads to malabsorption.

What are the causes of malabsorption in children?
Inadequate digestion

- Postgastrectomy
- Deficiency or inactivation of pancreatic lipase
- Exocrine pancreatic insufficiency
- Chronic pancreatitis
- Cystic fibrosis
- Pancreatic insufficiency - congenital or acquired
- Gastrinoma - acid inactivation of lipase
- Lactose intolerance
Reduced intraduodenal bile acid concentration / impaired micelle formation
Liver disease
- Parenchymal liver disease
- Cholestatic liver disease
Bacterial overgrowth syndrome
- Anatomic or functional stasis
- Interrupted enterohepatic circulation of bile salts
- Ileal resection
- Crohn's disease
Drugs (bind or precipitate bile salts) : calcium carbonate, neomycin, cholestyramine
Impaired mucosa absorption / mucosa loss or defect
Intestinal resection or bypass
- Inflammation, infiltration, or infection
- Celiac disease
- Crohn's disease
- Tropical sprue
- Amyloidosis
- Scleroderma
- Lymphoma
- Immuno proliferative small intestinal disease (IPSID)
- Eosinophilic enteritis
- Whipple's disease
- Folate and Vitamin B12 deficiency
- Infection: Giardiasis, Strongyloidiasis, Tuberculosis
- Graft vs. host disease
Genetic disorders
- Disaccharidase deficiency
- Agammaglobulinemia
- Abetalipoproteinemia
- Hartnup disease
- Cystinuria
Impaired nutrient delivery to and/or from intestine
Lymphatic obstruction
- Lymphoma
- Lymphangiectasia
Circulatory disorders
- Constrictive pericarditis
- Vasculitis
- Congestive heart failure
Endocrine and metabolic disorders
- Hyperthyroidism
- Adrenal insufficiency
- Diabetes mellitus
- Hypoparathyroidism
- Carcinoid syndrome

Most frequent causes of malabsorption in children in India
- Infections: Giardiasis, Strongyloidiasis, Tuberculosis
- Celiac sprue (Gluten sensitivity)
- Lactose intolerance
- Tropical sprue
- Chronic pancreatitis
- Lymphoma, Immunoproliferative small intestinal disease (IPSID)

Does an acute gastrointestinal infection lead to malabsorption?
Yes. Acute viral or bacterial gastrointestinal infection can give rise to transient malabsorption, most probably due to damage to small intestinal villi and microvilli.

Where are specific food items absorbed along the gastrointestinal tract?

Food ItemSite of maximal absorption
Jejunum and Ileum
CarbohydratesJejunum and Ileum
LipidsJejunum and Ileum
Duodenum and Jejunum
Jejunum and Ileum
Duodenum and Jejunum
Small intestine
Vitamin ASmall intestine
Vitamin B12
Folic acid
Vitamin CJejunum and Ileum
Vitamin DJejunum
Vitamin EJejunum and Ileum
Vitamin KJejunum and Ileum
WaterJejunum, Ileum, Colon

Contributor Information and Disclosures Saumil K. Shah
GASTROENTEROLOGIST, HEPATOLOGIST, ENDOSCOPIST, Lilavati Hospital And Research Centre, Mumbai, India

First Created : 2/20/2001
Contributor Information and Disclosures

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