2/26/2009

Malabsorption: etiology, pathogenesis and evaluation

Peter HR Green

DIFFERENTIAL SITES OF NORMAL ABSORPTION ABSORPTION • Coordination of gastric, small intestinal, • Fat, carbohydrate and protein can be pancreatic and biliary function absorbed along the entire length (22 feet) • Multiple mechanisms • Vitamins and minerals are absorbed at Fat different sites protein carbohydrate vitamins and minerals

NORMAL ABSORPTION

• Integrated and coordinated response involving different organs, enzymes, hormones, transport and secretory mechanisms Fat Protein • Great redundancy CHO

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ABSORPTION FAT MALABSORPTION

LUMINAL MUCOSAL REMOVAL • Luminal phase altered motility - chyme ppyancreatic insufficiency - pancreatic secretion – lipase, colipase micelle formation – bile salts, lecithin • Intestinal phase transport, chylomicron formation, secretion • Transport (lymphatic) phase

Pancreas FAT ABSORPTION FunctionalFunctional LipaseLipase Reserve Reserve

• GASTRIC PHASE lingual lipase • INTESTINAL luminal mucosal lymphatic (delivery)

FAT ABSORPTION FAT MALABSORPTION

• Luminal phase • Luminal phase chyme altered motility - chyme pancreatic insufficiency –cancer, ductal obstruction, pancreatic secretion – lipase, colipase chronic pancreatitis micelle formation – bile salts, lecithin biliary tract / liver disease – cirrhosis, bile duct cancer • Intestinal phase transport, chylomicron formation, secretion SMALL INTESTINAL BACTERIAL OVERGROWTH • Transport (lymphatic) phase

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SMALL INTESTINAL BACTERIAL OVERGROWTH FAT MALABSORPTION

• CONSEQUENCES BLIND LOOP SYNDROME -steatorrhea, diarrhea JEJUNAL DIVERTICULOSIS IMPAIRED MOTILITY -weight loss (sclerthoderma, celiac disease) -vitamin deficiency Deconjugation bile salts K –bleeding, A –night blindness

Rx antibiotics D –bone disease, E –neurological disorders ALL, OR ONLY ONE!!

FAT MALABSORPTION PROTEIN ABSORPTION

• INTESTINAL PHASE • Gastric events – acid, pepsin mucosal disease – celiac disease, tropical • Luminal events – pancreatic secretions sprue, Crohn’s disease, radiation, trypsin, chymotrypsin secreted as precursors abetaliporoteinemia, chylomicron retention and activated by brush border enzymes, disease, giardiasis then actively transported. • REMOVAL PHASE Lymphatic obstruction (lymphoma) • Rare congenital disorders of transport

ABSORPTION PROTEIN ABSORPTION

LUMINAL MUCOSAL REMOVAL LUMINAL MUCOSAL REMOVAL

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CARBOHYDRATE ABSORPTION

• Salivary amylase • Pancreatic amylase - prodtducts of fditi digestion malt ose, malt lttiotriose, and a - dextrins, some glucose - glucose actively absorbed - brush border enzymes digest oligosaccharides (lactase, sucrase) - fructose malabsorption

CARBOHYDRATE ABSORPTION

LUMINAL MUCOSAL REMOVAL

BLIND LOOP POOR SYNDROME MIXING ENZYMES, CHYME

ANTIBIOTICS ENZYMES

ZOLLINGER ELLISON SYNDROME MULTIPLE MECHANISMS OF DIARRHEA AND MALABSORPTION • Excessive water and acid production • Acidification of duodenal contents, deconjugation bile salts, inactivation of enzymes • Villous atrophy

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Consequences of resection

• Site of resection – distal bowel present – distal bowel absent • Extent/severity of disease • Residual disease • Adaptation of residual intestine • Age

MALABSORPTION DUE TO INFECTIONS • Giardiasis • Cryptosporidiasis • Strongyloides • Isospora • Mycobacterium avium

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Upper Endoscopy Histology – Strongyloides Stercoralis Strongyloides

Upper Endoscopy Isospora belli

Upper GI Series Mycobacterium avium

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Gallstones and renal stones

• Gall stones are related to bile salt Malabsorption due to ileal and phospholipid depletion as a result of fat malabsorption and bile disease/resection salt loss • Renal stones are related to excess oxalate absorption as a result of intraluminal soap formation and depletion of calcium ions

Crohn’s ileitis

MALABSORPTION Bile salts Vitamin B12

EVALUATION OF MALABSORPTION • CONSEQUENCES weight, BMI ferritin, folate, B12 (methyl malonic acid , homocysteine) zinc, copper calcium, vitamin D, PTH

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EVALUATION OF MALABSORPTION • CAUSE PROXIMAL Vs DISTAL ?steatorrhea (pancreas , biliar y, intestinal ) Radiology (small intestine, CAT, USG) Breath tests (bacterial overgrowth, lactose, fructose) Biopsy Video capsule endoscopy

EVALUATION OF MALABSORPTION • STOOL O&P GIARDIA ANTIGEN FECAL FAT – quantitative, qualitative PANCREATIC ELASTASE

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