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 Vitamin K 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 Iron 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. 2 x (stool [Na+] + [stool K+]) ≤ stool osmolality
Stool Osmotic Gap
Useful in differentiating secretory from osmotic diarrhea
2 x (stool [Na+] + [stool K+]) ≤ stool osmolality
Normal: 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

13. Radiologic Examination
Schilling Test
Urinary 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 58Co-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 Chronic Pancreatitis Achlorydia
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 58Co-Cbl With Intrinsic Factor With Pancreatic Enzymes
After 5 Days of Antibiotics
Pernicious anemia
Reduced
Normal
Chronic pancreatitis
Bacterial
overgrowth
Ileal disease

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 Test
Duodenal Mucosal Biopsy
Chronic pancreatitis
Normal
50% abnormal; if abnormal, normal with pancreatic enzymes
Bacterial overgrowth syndrome
Normal or only modestly abnormal
Often abnormal; if abnormal, normal after antibiotics
Usually normal
Ileal disease
Abnormal
Celiac sprue
Decreased
Abnormal: probably "flat"
Intestinal lymphangiectasia
Abnormal: "dilated lymphatics"

20. Differential Diagnosis for Chronic Diarrhea: Approach to a Patient with Malabsorption
CC: Diarrhea 1 month duration
Prolonged fast (>24h)
Osmotic Diarrhea (>50 osmotic gap difference)
SI Mucosal Biopsy
Diagnosis: Cause of Malabsorption
Secretory Diarrhea (<25 osmotic gap difference)