malabsorption

Disorders of Malabsorption

Malabsorption
It is a descriptive term of many diseases and is not a diagnosis Result from either a defect in nutrient digestion in the intestinal lumen or mucosal absorption

Malabsorption

Malabsorptive disorders can be categorized into 1-Generalized mucosal abnormalities resulting in multiple nutrient malabsorption 2-Specific nutrient malabsorption disorder ( carbohydrate, fat, protein, vitamin and mineral malabsorption)

Malabsorptive disorders with generalized mucosal defects

Celiac diseaseCow’s milk allergyMicrovillous inclusion diseaseTufting enteropathyLymphangiectasiaShort bowel syndromeChronic malnutrition Congenital immunodeficiency disorders HIV Parasitic infections Tropical sprue Bacterial overgrowth

Specific nutrient malabsorptive disorder

Carbohydrate malabsorption - lactase deficiency (congenital, secondary) Congenital sucrase-isomaltase deficiency Glucose- galactose malabsorption Protein malabsorption - Enterokinase deficiency - Amino acid transport defect (eg;Hartnup disease )

Fat malabsorption -Pancreatic exocrine insufficiency (cystic fibrosis, shwachman diamond syndrome, chronic pancreatitis) -liver and biliary disorders - abetalipoproteinemia

Specific nutrient malabsorptive disorder

Mineral and vitamin malabsorption -Congenital chloride diarrhea -Congenital sodium absorption defect -Acrodermatitis enteropathica -Menke disease -Vitamin D dependent rickets -Vitamin B12 malabsorption

Malabsorption

Clinical manifestations: -Diarrhea -Abdominal distention -Failure to thrive -edema -digital clubbing -abnormal hair
-muscle wasting -stomatitis and glossitis -signs of rickets -skin bruises

Malabsorption

Diarrhea is the main presentation of malabsorption:Onset: at birth, relation to foodCharacter: offensive, oily, watery,…

Evaluation of children with malabsorption

CBC and blood film anemia, lymphopenia (lymphangiectasia), neutropenia (shwachman syndrome), acanthocytosis (abetalipoproteinemia) Stool: Leukocytes and occult blood Parasites PH and reducing substances

Evaluation of children with malabsorption

Celiac serology Albumin level Ca, Mg, zinc Iron level, folic acid level, Vit B12 Vit D, E, A Prothrombin time Upper endoscopy

Investigations for Carbohydrate malabsorption

Clinitest: Detect reducing substances in the stool stool PH less than 5.6 Carbohydrate reach the bowel where they are degraded to Hydrogen gas+ CO2+ organic acids

Investigations for Carbohydrate malabsorption

3-Breath hydrogen test Ingestion of carbohydrate load (sucrose or lactose)1-2g/kg, sugar will not be ingested in the small bowel and passes to the colon and then metabolized by normal flora into hydrogen gas which will be detected in the breath

Investigations for Carbohydrate malabsorption

4-Small bowel mucosal biopsies Low mucosal disaccharidase levels in primary disaccharidase deficiency (lactase, sucrase, maltase)


Investigations for fat malabsorption
Sudan test -Best screening method -Mixing the stool with sudan red stain, fat droplets will separate and be identified, more than 6-8 droplets / low power field is abnormal 72-hr quantitative fecal fat test - The gold standard to confirm steatorrhea Dietary record is used to calculate fat intake for 3 days, stool is collected, excretion of more than 7% is abnormal

Investigations for Gastrointestinal Protein loss

Dietary and endogenous proteins are almost absorbedMajority of stool nitrogen is derived from gut bacterial proteinsAlbumin Level:-GI loss of protein manifests as hypoalbuminemia-low albumin occur due to other factorsα1-antitrypsin:-Useful screening test for protein losing enteropathy -Unlike albumin, is resistant to digestion in the GIT-High levels in the stool indicate protein losing enteropathy

Investigations for Pancreatic Exocrine function

Most common is Cystic fibrosis Sweat chloride test Genetic testing Fecal elastase: -Sensitive test to assess exocrine pancreatic function -endoprotease that is human and pancreas specific, not altered by pancreatic enzyme replacement Serum Trypsinogen Duodenal aspirate Analysis of bicarbonate, trypsinogen and lipase after secretin stimulation