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Malabsorption: etiology,pathogenesis and

evaluation

Peter HR Green

NORMAL ABSORPTION

• Coordination of gastric, small intestinal,pancreatic and biliary function

• Multiple mechanismsFatproteincarbohydratevitamins and minerals

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NORMAL ABSORPTION

• Integrated and coordinated responseinvolving different organs, enzymes,hormones, transport and secretorymechanisms

• Great redundancy

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DIFFERENTIAL SITES OFABSORPTION

• Fat, carbohydrate and protein can beabsorbed along the entire length (22 feet)

• Vitamins and minerals are absorbed atdifferent sites

FatProteinCHO

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ABSORPTIONLUMINAL MUCOSAL REMOVAL

FAT ABSORPTION

• GASTRIC PHASElingual lipase

• INTESTINALluminalmucosallymphatic (delivery)

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FAT ABSORPTION

• Luminal phase chyme pancreatic secretion – lipase, colipase micelle formation – bile salts, lecithin

• Intestinal phase transport, chylomicron formation, secretion

• Transport (lymphatic) phase

FAT MALABSORPTION

• Luminal phase altered motility - chyme pancreatic insufficiency - pancreatic secretion– lipase, colipase micelle formation – bile salts, lecithin

• Intestinal phase transport, chylomicron formation, secretion• Transport (lymphatic) phase

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Functional Lipase ReservePancreas

Functional Lipase Reserve

FAT MALABSORPTION

• Luminal phase altered motility - chyme pancreatic insufficiency –cancer, ductal obstruction,

chronic pancreatitis biliary tract / liver disease – cirrhosis, bile duct cancer

SMALL INTESTINAL BACTERIAL OVERGROWTH

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SMALL INTESTINAL BACTERIALOVERGROWTH

BLIND LOOP SYNDROMEJEJUNAL DIVERTICULOSIS

IMPAIRED MOTILITY(sclerthoderma, celiac disease)

Deconjugation bile salts

Rx antibiotics

FAT MALABSORPTION

• INTESTINAL PHASE mucosal disease – celiac disease, tropicalsprue, Crohn’s disease, radiation,abetaliporoteinemia, chylomicron retentiondisease, giardiasis

• REMOVAL PHASELymphatic obstruction (lymphoma)

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ABSORPTION

LUMINAL MUCOSAL REMOVAL

FAT MALABSORPTION

• CONSEQUENCES-steatorrhea, diarrhea-weight loss-vitamin deficiency K –bleeding, A –night blindness D –bone disease, E –neurological disorders

ALL, OR ONLY ONE!!

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PROTEIN ABSORPTION

• Gastric events – acid, pepsin• Luminal events – pancreatic secretions

trypsin, chymotrypsin secreted asprecursors and activated by brush borderenzymes, then actively transported.

• Rare congenital disorders of transport

PROTEIN ABSORPTION

LUMINAL MUCOSAL REMOVAL

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CARBOHYDRATE ABSORPTION

• Salivary amylase• Pancreatic amylase

- products of digestion maltose, maltotriose, and a -dextrins, some glucose

- glucose actively absorbed- brush border enzymes digest oligosaccharides (lactase, sucrase)- fructose malabsorption

CARBOHYDRATE ABSORPTION

LUMINAL MUCOSAL REMOVAL

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BLIND LOOP SYNDROME

ANTIBIOTICS

POORMIXING

ENZYMES, CHYME

ENZYMES

ZOLLINGER ELLISONSYNDROME

MULTIPLE MECHANISMS OFDIARRHEA AND MALABSORPTION

• Excessive water and acid production• Acidification of duodenal contents,

deconjugation bile salts, inactivation ofenzymes

• 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 TOINFECTIONS

• Giardiasis• Cryptosporidiasis• Strongyloides• Isospora• Mycobacterium avium

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Upper Endoscopy Strongyloides

Upper Endoscopy

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Upper GI Series

Histology – Strongyloides Stercoralis

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Isospora belli

Mycobacterium avium

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Malabsorption due to ilealdisease/resection

Crohn’s ileitis

MALABSORPTIONBile salts

Vitamin B12

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Gallstones and renal stones

• Gall stones are related to bile saltand phospholipid depletion as aresult of fat malabsorption and bilesalt loss

• Renal stones are related to excessoxalate absorption as a result ofintraluminal soap formation anddepletion of calcium ions

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EVALUATION OFMALABSORPTION

• CONSEQUENCESweight, BMIferritin, folate, B12 (methyl malonic acid,homocysteine)zinc, coppercalcium, vitamin D, PTH

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EVALUATION OFMALABSORPTION

• CAUSEPROXIMAL Vs DISTAL?steatorrhea (pancreas, biliary, intestinal)

Radiology (small intestine, CAT, USG)Breath tests (bacterial overgrowth, lactose, fructose)BiopsyVideo capsule endoscopy

EVALUATION OFMALABSORPTION

• STOOLO&PGIARDIA ANTIGENFECAL FAT – quantitative, qualitativePANCREATIC ELASTASE