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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-Cbl W/ IF W/ pancreatic enzymes After 5 days of antibiotic Reduced Normal Reduced Reduced Chronic Reduced Pancreatitis Reduced Normal Reduced Bacterial overgrowth syndrome Reduced Reduced Normal Reduced Reduced Reduced Pernicious anemia Ileal disease Reduced Reduced
