Introduction

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 Useful in differentiating secretory from osmotic diarrhea • Normal: 290-300 mosmol/kg H20 • 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 2 x (stool [Na+] + [stool K+]) ≤ stool osmolality

14. Cobalamin Absorption

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

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

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