2/26/2009

1

Malabsorption: etiology, pathogenesis and

l tievaluation

Peter HR Green

NORMAL ABSORPTION

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

• Multiple mechanismsFatproteinproteincarbohydratevitamins and minerals

2/26/2009

2

NORMAL ABSORPTION

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

• Great redundancy• Great redundancy

2/26/2009

3

DIFFERENTIAL SITES OF ABSORPTION

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

• Vitamins and minerals are absorbed at different sites

FatProteinCHOCHO

2/26/2009

4

ABSORPTIONLUMINAL MUCOSAL REMOVAL

FAT ABSORPTION

• GASTRIC PHASE• GASTRIC PHASE lingual lipase

• INTESTINALluminal

lmucosallymphatic (delivery)

2/26/2009

5

FAT ABSORPTION

• Luminal phase• Luminal phasechymepancreatic secretion – lipase, colipasemicelle formation – bile salts, lecithin

• Intestinal phaseIntestinal phasetransport, chylomicron formation, secretion

• Transport (lymphatic) phase

FAT MALABSORPTION

• Luminal phase• Luminal phasealtered motility - chyme pancreatic insufficiency - pancreatic secretion –

lipase, colipasemicelle formation – bile salts, lecithin

I t ti l h• Intestinal phasetransport, chylomicron formation, secretion

• Transport (lymphatic) phase

2/26/2009

6

Functional Lipase ReserveFunctional Lipase ReservePancreasPancreas

Functional Lipase Reserve

FAT MALABSORPTION

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

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

SMALL INTESTINAL BACTERIAL OVERGROWTH

2/26/2009

7

SMALL INTESTINAL BACTERIAL OVERGROWTH

BLIND LOOP SYNDROMEJEJUNAL DIVERTICULOSIS

IMPAIRED MOTILITY(sclerthoderma, celiac disease)

Deconjugation bile salts

Rx antibiotics

FAT MALABSORPTION

• INTESTINAL PHASE• INTESTINAL PHASEmucosal disease – celiac disease, tropical

sprue, Crohn’s disease, radiation, abetaliporoteinemia, chylomicron retention disease, giardiasisREMOVAL PHASE• REMOVAL PHASELymphatic obstruction (lymphoma)

2/26/2009

8

ABSORPTION

LUMINAL MUCOSAL REMOVAL

FAT MALABSORPTION

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

disordersALL, OR ONLY ONE!!

2/26/2009

9

PROTEIN ABSORPTION

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

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

• Rare congenital disorders of transport

PROTEIN ABSORPTION

LUMINAL MUCOSAL REMOVAL

2/26/2009

10

CARBOHYDRATE ABSORPTION

• Salivary amylase• 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

2/26/2009

11

2/26/2009

12

BLIND LOOPSYNDROME

ANTIBIOTICS

POORMIXING

ENZYMES, CHYME

ENZYMES

ZOLLINGER ELLISON SYNDROME

MULTIPLE MECHANISMS OFMULTIPLE MECHANISMS OF DIARRHEA AND MALABSORPTION

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

deconjugation bile salts, inactivation of j g ,enzymes

• Villous atrophy

2/26/2009

13

2/26/2009

14

2/26/2009

15

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• Giardiasis• Cryptosporidiasis• Strongyloides• Isospora

M b t i i• Mycobacterium avium

2/26/2009

16

Upper EndoscopyStrongyloides

Upper Endoscopy

2/26/2009

17

Upper GI Series

Histology – Strongyloides Stercoralis

2/26/2009

18

Isospora belli

Mycobacterium avium

2/26/2009

19

Malabsorption due to ileal disease/resection

Crohn’s ileitis

MALABSORPTIONBile salts

Vitamin B12

2/26/2009

20

Gallstones and renal stones

• Gall stones are related to bile salt and phospholipid depletion as a result of fat malabsorption and bile salt loss

• Renal stones are related to excess oxalate absorption as a result ofoxalate absorption as a result of intraluminal soap formation and depletion of calcium ions

2/26/2009

21

EVALUATION OF MALABSORPTION

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

2/26/2009

22

EVALUATION OF MALABSORPTION

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

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

EVALUATION OF MALABSORPTION

• STOOL• STOOLO&PGIARDIA ANTIGENFECAL FAT – quantitative, qualitativePANCREATIC ELASTASE