Malabsorption Approach to the patient

Hx, Sx, initial preliminary observation Extensive small-intestinal resection for mesenteric ischemia –Short bowel syndrome Steatorrhea with chronic alcohol intake and chronic pancreatitis –Pancreatic exocrine dysfunction

Site specific active transport process Throughout SI (Proximal>Distal) –Glucose, amino acids, lipids Proximal SI (especially duodenum) –Calcium –Iron –Folate Ileum –Cobalamin –Bile acids

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

Steatorrhea Quantitative stool fat determination (72 hours) –Gold standard Qualitative Sudan III stain –Doesn’t 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

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

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

Diagnostic tests

Schilling’s test Determines cause of cobalamin malabsorption Asses the integrity of the –Stomach Cobalamin:R-binder protein complex (acidic milieu) –Pancreas Protease enzyme that splits the complex –Ileum Requires intrinsic factor to be absorbed in the brush border of the ileal enterocytes

Schilling’s test Procedure: –Oral: 58Co-labeled cobalamin –IM 1 hour after: 1 mg cobalamin Saturation of hepatic cobalamin binding sites –Collect urine for 24 hours Needs normal renal and bladder function –If abnormal (<10%), Co-labeled cobalamin should be administered on another occasion either bound to IF, pancreatic enzymes, or after a 5 day course of antibiotic (tetracycline)

Variation of Schilling’s test Detection of achlorhydria Labeled cobalamin is cooked with scrambled egg.

Abnormal Schilling’s test Pernicious anemia –Atrophy of gastric parietal cells Absence of gastric acid and IF Chronic pancreatitis –Deficiency of pancreatic protease Achlorhydria –Failure to release cobalamin from food Bacterial overgrowth syndromes –Stasis in the SI (bacterial utilization of cobalamin) Ileal dysfunction –Due to inflammation and prior intestinal resection –Impaired cobalamin-IF uptake by ileal intestinal epithelial cells

Differences 58Co-CblW/ IFW/ pancreatic enzymes After 5 days of antibiotic Pernicious anemia ReducedNormalReduced Chronic Pancreatitis Reduced NormalReduced Bacterial overgrowth syndrome Reduced Normal Ileal disease Reduced