mlb ti tilmalabsorption: etiology, pathogenesis
TRANSCRIPT
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