mlb ti tilmalabsorption: etiology, pathogenesis

M l b ti ti lMalabsorption: etiology, pathogenesis andpathogenesis and

evaluation

Peter HR Green

NORMAL ABSORPTION

• Coordination of gastric, small intestinal, pancreatic and biliary functionp y

• Multiple mechanismsFatFatproteincarbohydratevitamins and minerals

NORMAL ABSORPTION

• Integrated and coordinated response involving different organs enzymesinvolving different organs, enzymes, hormones, transport and secretory mechanismsmechanisms

• Great redundancy

DIFFERENTIAL SITES OFDIFFERENTIAL SITES OF ABSORPTION

• Fat, carbohydrate and protein can be absorbed along the entire length (22 feet)g g ( )

• Vitamins and minerals are absorbed at different sitesdifferent sites

FatFatProteinCHO

ABSORPTIONLUMINAL MUCOSAL REMOVAL

FAT ABSORPTION

• GASTRIC PHASE lingual lipaselingual lipase

• INTESTINALl i lluminalmucosallymphatic (delivery)

FAT ABSORPTION

• Luminal phasechymechymepancreatic secretion – lipase, colipasemicelle formation bile salts lecithinmicelle formation – bile salts, lecithin

• Intestinal phasetransport, chylomicron formation, secretion

• Transport (lymphatic) phasep ( y p ) p

FAT MALABSORPTION

• Luminal phasealtered motility - chyme y ypancreatic insufficiency - pancreatic secretion –

lipase, colipasemicelle formation – bile salts, lecithin

• Intestinal phasetransport, chylomicron formation, secretion

• Transport (lymphatic) phaseTransport (lymphatic) phase

Functional Lipase ReserveFunctional Lipase ReservePancreasPancreas

Functional Lipase ReserveFunctional Lipase ReserveFunctional Lipase Reserve

FAT MALABSORPTION

• Luminal phasealtered motility - chyme y ypancreatic insufficiency –cancer, ductal obstruction,

chronic pancreatitisbiliary tract / liver disease – cirrhosis, bile duct cancer

SMALL INTESTINAL BACTERIAL OVERGROWTHSMALL INTESTINAL BACTERIAL OVERGROWTH

SMALL INTESTINAL BACTERIALSMALL INTESTINAL BACTERIAL OVERGROWTH

BLIND LOOP SYNDROMEJEJUNAL DIVERTICULOSIS

IMPAIRED MOTILITY(sclerthoderma, celiac disease)

Deconjugation bile salts

Rx antibioticsRx antibiotics

FAT MALABSORPTION

• INTESTINAL PHASEmucosal disease – celiac disease, tropical , p

sprue, Crohn’s disease, radiation, abetaliporoteinemia, chylomicron retention disease, giardiasis

• REMOVAL PHASELymphatic obstruction (lymphoma)

ABSORPTIONABSORPTION

LUMINAL MUCOSAL REMOVAL

FAT MALABSORPTION

• CONSEQUENCES-steatorrhea, diarrhea,-weight loss-vitamin deficiency yK –bleeding, A –night blindnessD –bone disease E –neurologicalD bone disease, E neurological

disordersALL, OR ONLY ONE!!, O O O

PROTEIN ABSORPTION

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

trypsin, chymotrypsin secreted as precursors and activated by brush border enzymesand activated by brush border enzymes, then actively transported.

• Rare congenital disorders of transport

PROTEIN ABSORPTIONPROTEIN ABSORPTION

LUMINAL MUCOSAL REMOVAL

CARBOHYDRATE ABSORPTION

• Salivary amylase• Pancreatic amylasePancreatic amylase

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

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

CARBOHYDRATE ABSORPTIONCARBOHYDRATE ABSORPTION

LUMINAL MUCOSAL REMOVAL

BLIND LOOPSYNDROME

POORMIXING

ENZYMES CHYME

ANTIBIOTICSENZYMES, CHYME

ENZYMES

ZOLLINGER ELLISONZOLLINGER ELLISON SYNDROME

MULTIPLE MECHANISMS OF DIARRHEA AND MALABSORPTION

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

deconjugation bile salts, inactivation of enzymesenzymes

• Villous atrophy

Consequences of resectionConsequences of resection

• Site of resection• Site of resection – distal bowel present

di t l b l b t– distal bowel absent• Extent/severity of disease• Residual disease• Adaptation of residual intestineAdaptation of residual intestine• Age

MALABSORPTION DUE TOMALABSORPTION DUE TO INFECTIONS

• Giardiasis• CryptosporidiasisCryptosporidiasis• Strongyloides

I• Isospora• Mycobacterium avium

Upper EndoscopyStrongyloidesStrongyloides

Upper Endoscopypp py

Upper GI Seriespp

Histology – Strongyloides Stercoralisgy gy

Isospora belli

Mycobacterium aviumMycobacterium avium

Malabsorption due to ileal disease/resection

Crohn’s ileitis

MALABSORPTIONBile saltsi i 12Vitamin B12

Gallstones and renal stonesGallstones and renal stones

• Gall stones are related to bile salt• Gall stones are related to bile salt and phospholipid depletion as a result of fat malabsorption and bileresult of fat malabsorption and bile salt lossR l t l t d t• Renal stones are related to excess oxalate absorption as a result of i t l i l f ti dintraluminal soap formation and depletion of calcium ions

EVALUATION OFEVALUATION OF MALABSORPTION

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

EVALUATION OFEVALUATION OF MALABSORPTION

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

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

EVALUATION OFEVALUATION OF MALABSORPTION

• STOOLO&PO&PGIARDIA ANTIGENFECAL FAT – quantitative qualitativeFECAL FAT quantitative, qualitativePANCREATIC ELASTASE