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Introduction Malabsorption. Malabsorption Syndrome Diminished intestinal absorption of one or more dietary nutrients Not an adequate final diagnosis Most.

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Presentation on theme: "Introduction Malabsorption. Malabsorption Syndrome Diminished intestinal absorption of one or more dietary nutrients Not an adequate final diagnosis Most."— Presentation transcript:

1 Introduction Malabsorption

2 Malabsorption Syndrome Diminished intestinal absorption of one or more dietary nutrients Not an adequate final diagnosis Most are associated with steatorrhea – Increase in stool fat excretion of >6% dietary fat intake

3 Approach to the Patient Malabsorption

4 History, Symptoms and Initial Preliminary Observation Extensive small-intestinal resection for mesenteric ischemia – Short bowel syndrome Steatorrhea with chronic alcohol intake and chronic pancreatitis – Pancreatic exocrine dysfunction

5 Active Transport of Site-specific Dietary Nutrient Absorption Throughout SI (Proximal>Distal) – Glucose, amino acids, lipids Proximal SI (esp. duodenum) – Calcium – Iron – Folate Ileum – Cobalamin – Bile acids

6 Adaptation Morphologic and functional Due to segmental resection Secondary to the presence of luminal nutrients and hormonal stimuli Critical for survival

7 Steatorrhea Quantitative stool fat determination (72 hours) – Gold standard Qualitative Sudan III stain – Does not establish degree of fat malabsorption – For preliminary screening studies Blood, breath, and isotropic test – Do not directly measure fat absorption – Excellent sensitivity only with obvious steatorrhea – Not survived transition from research laboratory to commercial application

8 Laboratory Testing Vitamin D malabsorption – Evidence of metabolic bone disease – Elevated serum ALP – Reduced serum calcium Vitamin K malabsorption – Elevated prothrombin time – Without liver disease – No intake of anti-coagulants

9 Laboratory testing Cobalamin/Folate malabsorption – Macrocytic anemia Iron malabsorption – Iron deficiency anemia – No occult bleeding from GIT – Non-menstruating female – Exclusion of celiac sprue Iron is absorbed in the proximal SI

10 Diagnostic Procedures Malabsorption

11 Diagnosis of Malabsorption Effect of prolonged (>24h) fasting on stool output – Osmotic diarrhea Decrease in stool output: Presumptive evidence that diarrhea is related to malabsorption – Secretory diarrhea Persistence of stool output: Not due to nutrient deficiency

12 Stool Osmotic Gap Normal: 290-300 mosmol/kg H 2 0 Significant osmotic gap – Suggests the presence of anions other than Na and K are present in the stool, presumably the cause of diarrhea Diff >50: osmotic gap present, dietary nutrient is not absorbed Diff <25: dietary nutrient is not responsible for the diarrhea Useful in differentiating secretory from osmotic diarrhea 2 x (stool [Na + ] + [stool K + ]) ≤ stool osmolality

13 Schilling TestUrinary D-Xylose Test Radiologic Examination Use -determine the cause for cobalamin malabsorption -assess the integrity of stomach, pancreas, and colon -test for carbohydrate absorption -assessment of proximal small-intestinal mucosal function -evaluation of the patient with presumed or suspected malabsorption Procedure -performed by administering 58 Co- labeled cobalamin orally and collecting urine for 24 h - performed by giving 25 g D-xylose and collecting urine for 5 h -performed with the examination of the esophagus to duodenal bulb -insufficient barium is given to the patient Abnormal Findings <10% excretion in 24 h<4.5 g excretion Ex. strictures & fistulas (Crohn’s disease), Disadvantage - infrequently performed because of the unavailability of human intrinsic factor - diminished use due to ease of obtaining a mucosal biopsy by endoscopy and false- negative rate -abnormalities are rarely seen with current barium suspensions, skilled personnel required

14 Cobalamin Absorption Dietary cobalamin in meat Bound to R- binder protein in stomach Complex bound in acid milieu in the stomach Uptake of cobalamin in receptors in brush border of ileal enterocytes Pancreatic protease enzymes split cobalamin and binding protein Cobalamin enters the proximal small intestine and binds to intrinsic factor

15 Schilling Test Pernicious Anemia – Atrophy of gastric parietal cells lead to absence of gastric acid and intrinsic factor secretion Chronic Pancreatitis – Deficiency of pancreatic proteases to split the cobalamin-R binder complex Achlorydia – Absence of another factor secreted with acid that is responsible for splitting cobalamin from the proteins in food Bacterial Overgrowth syndromes – Bacterial utilization of cobalamin Ileal dysfunction – Impaired cobalamin – intrinsic factor uptake

16 Schilling Test 58 Co-Cbl With Intrinsic Factor With Pancreatic Enzymes After 5 Days of Antibiotics Pernicious anemia ReducedNormalReduced Chronic pancreatitis Reduced NormalReduced Bacterial overgrowth Reduced Normal Ileal diseaseReduced

17 Biopsy of Small-Intestinal Mucosa Essential in the evaluation of a patient with documented steatorrhea or chronic diarrhea Preferred method to obtain histologic material of proximal small-intestinal mucosa Indications: – Evaluation of a patient either with documented or suspected steatorrhea or with chronic diarrhea – Diffuse or focal abnormalities of the small intestine defined on a small-intestinal series

18 Biopsy Lesions and Findings

19 Results of Diagnostic Studies in Different Causes of Steatorrhea D-Xylose Test Schilling TestDuodenal Mucosal Biopsy Chronic pancreatitis Normal50% abnormal; if abnormal, normal with pancreatic enzymes Normal Bacterial overgrowth syndrome Normal or only modestly abnormal Often abnormal; if abnormal, normal after antibiotics Usually normal Ileal diseaseNormalAbnormalNormal Celiac sprueDecreasedNormalAbnormal: probably "flat" Intestinal lymphangiectasia Normal Abnormal: "dilated lymphatics"

20 Differential Diagnosis for Chronic Diarrhea: Approach to a Patient with Malabsorption

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