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8/6/2019 Malabsorption A Clinical Approach
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Malabsorption
A Clinical Approach
John K. DiBaise, MD
Associate Professor of MedicineMayo Clinic Arizona
2007 AGA GI Fellows Nutrition Course
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Outline
Normal digestion and absorption
Classification of malabsorption
Tests of malabsorption
Clinical approach to diagnosis
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Malabsorption vs.
Maldigestion
malabsorption defect in mucosalphase
maldigestion defect in intraluminalphase
Decreased intestinal absorption of
macronutrients and/or micronutrients
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Normal Digestion and
Absorption Mechanical mixing
Enzyme and bilesalt production
Mucosal function
Blood supply
Intestinal motility
Commensal gutflora
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Fat Digestion and
Absorption
Ebert EC. Dis Month 2001;47:49
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Carbohydrate and Protein
Digestion and AbsorptionProteinProtein OligopeptidesOligopeptides AAAA
CHOCHO OligosaccharidesOligosaccharides SugarsSugars
Pancreatic amylase Mucosal disaccharidases
Pancreatic proteases Mucosal peptidases
Digestion Absorption Distribution
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Classification of
Malabsorption Luminal
Mucosal
Postabsorptive
Overt
Subclinical
Asymptomatic
Global/Total
Partial
Selective
CHO
Protein
Fat
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Classification of
Malabsorption Luminal phase
Substrate hydrolysis Digestive enzyme deficiency/inactivation, inadequate mixing
Fat solubilization Diminished bile salt synthesis/secretion, increased loss
Luminal availability of nutrients Diminished gastric acid/intrinsic factor, bacterial
consumption
Mucosal phase Brush border hydrolysis Epithelial transport
Postabsorptive processing Enterocyte, lymphatic
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Mechanisms of Fat
Malabsorption Pancreatic insufficiency
Bile acid deficiency
Small intestinal bacterial overgrowth
Loss of absorptive surface area
Defective enterocyte function Lymphatic disorders
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Mechanisms of
Carbohydrate Malabsorption Selective disaccharidase deficiency
Disruption of brush border/enterocytefunction
Loss of mucosal surface area
Pancreatic insufficiency
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Mechanisms of Protein
Malabsorption Pancreatic insufficiency
Disorders with impaired enterocytefunction
Disorders with decreased absorptivesurface
Protein-losing enteropathy
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Clinical Presentation
Diarrhea
Steatorrhea
Weight loss
Bloating, distension, gas,borborygmi
Anorexia or hyperphagia Nausea, vomiting
Abdominal discomfort
Muscle atrophy
Edema
Signs/symptoms ofspecific vitamindeficiencies
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History and Exam
Prior GI surgery
h/o chronic pancreatitis
h/o liver, GI disorder h/o CTD, diabetes
h/o radiation therapy
Diet and medications
Alcohol/drugs h/o chronic sinus or
respiratory infections
Recent travel history
Timing of onset
Bowel habits/stoolcharacteristics
Associated GI andsystemic complaints
Evidence of malnutritionor micronutrientdeficiencies on exam
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Overview of Tests for
Malabsorption Blood tests
Fecal fat determination
Imaging studies
Endoscopy with biopsy and aspirate
Breath tests
D-xylose test, Schilling test,Secretin/CCK test
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Screening Laboratory
Tests Blood tests
CBC
Electrolytes, Mg,Phos, Ca
Albumin, protein
Vitamin B12, Folate,
Iron Liver tests
PT/INR, cholesterol
Carotene (?)
Stool tests
Inspection
Hemoccult O&P
Qualitative fat
everything comesdown to poo...
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Fecal Fat Determination
Quantitative Gold standard to diagnose
maldigestion
72 hour collection optimal
Normal < 7 g/day
Limited use in clinical practice due toissues with collection/processing
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Fecal Fat Determination
Qualitative Random spot sample
Qualitative (Sudan stain)
Semi-quantitative (#/size of droplets) Acid steatocrit
Less sensitive for mild-moderatesteatorrhea
Variable reproducibility
Helpful only if abnormal
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D-xylose Test
Indicates malabsorption secondary tomucosal dysfunction
Oral load with 25 g D-xylose 5 hr urine collection (normal > 4 g)
1 hr and 3 hr serum samples (normal > 20mg/dl at 1 hr, > 18.5 mg/dl at 3 hr)
Numerous factors affect results
Role in clinical practice controversial ? Use in special populations
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Vitamin B12 Absorption
and Schilling Test Determine etiology of
B12 deficiency 1 mcg radiolabeled
cynanocobalaminingested and 1 mg non-labeled B12 administeredIM
24 hr urine collection Recovery of < 9%
abnormal Numerous causes of
false positives/negatives
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4Stages of the Schilling Test
Condition Stage 1
(B12)
Stage 2
(IF)
Stage 3
(enzymes)
Stage 4
(antibx)
B12Malabsorption Decreased
Perniciousanemia
Decreased Normal
Chronic
pancreatitis
Decreased Decreased Normal
SIBO Decreased Decreased Decreased Normal
TI resection Decreased Decreased Decreased Decreased
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Direct Pancreatic Function
Tests Gold standard
Quantitative stimulation tests using either
secretin or CCK or test (Lundh) meal Requires Dreiling tube placed into duodenum
with collection of contents for an hour
Analyzed for bicarbonate (secretin) or
amylase/lipase/trypsin (CCK) Low concentrations (< 80-90 mEq/L HCO3; 105 cfu/ml
Many limitations
Invasive
Expensive Contamination
Many bacterial uncultivatable
Difficulty culturing anaerobes
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Imaging Studies
Barium contrast small bowel series Anatomical lesions, transit
Flocculation, decreased folds,segmentation, dilation
CT/MR enterography Detect bowel and pancreatic lesions
Enteroscopy, VCE, high resolutionmagnification endoscopy,chromoendoscopy
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Imaging Studies
ERCP Detect ductal abnormalities Other diagnostic/therapeutic
applications MRCP
Detect ductal and parenchymalabnormalities
EUS Detect ductal and parenchymalabnormalities
Allows tissue sampling Interobserver variability
problematic
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Endoscopy and Small Bowel
BiopsyVisual assessment
Decreased folds,
scalloping, mosaic pattern,frosted appearance,inflammatory changes
Histologic assessment
Diagnostic
Supportive of diagnosis
Normal
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Tests of Fat Malabsorption
Fecal fat collection
Spot fecal fat
14C-triolein, 13C-triglyceride breath tests
Near infrared reflectance analysis (NIRA)
Can measure fecal fat, nitrogen and CHO As accurate but less time consuming then 72
hr fecal fat collection
Not widely available
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Tests of Carbohydrate
Malabsorption Oral breath tests
Quantitative analysis of fecal CHO
Stool pH
Oral tolerance tests
Direct assay of mono- anddisaccharidases
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Protein-Losing Enteropathy
Characterized by excessive loss ofserum proteins into the gut
Hypoproteinemia, hypoalbuminemia,edema, muscle atrophy
May occur as isolated phenomenon or
part of global malabsorption Need to r/o malnutrition, nephrosis, liver
disease
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Conditions Associated with
Protein-Losing Enteropathy Mucosal disease
IBD, Celiac, Whipples,Tropical sprue,
Menetriers, GImalignancy,chemotherapy,eosinophilic dz, SIBO
Lymphatic obstruction Lymphangiectasia,
lymphoma, constrictivepericarditis, Crohns,radiation, Fontan
procedure
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Tests of Protein
Malabsorption Nutrient balance studies with fecal
nitrogen measurement
Radioisotopic methods 51Cr-labeled albumin
99mTc-labeled transferrin
125I-labeled albumin Indirect methods
Fecal E-1 antitrypsin clearance (> 25 mg/d)
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Terminal Ileal Resection
and Malabsorption< 100 cm
> 100cm
Bile Acid
Fat
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Take Home PointsThree Major Malabsorptive
Conditions
Small bowel mucosal disease
Small bowel bacterial overgrowth
Pancreatic insufficiency
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Take Home PointsApproach to Suspected
Malabsorption History
Physical exam
Routine screening labs Stool analysis
Selective tests based on above findings
Treat based on underlying disease ortype of malabsorption
H2 breath tests, Celiac Abs, Abd imaging, EGD w/bx, Colon w/bx,PFT, ERCP/MRCP/EUS, Angio, Fecal E1-AT, Fat pad aspirate
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Cases
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Case 1
47 yo man h/o alcoholism c/o constant vagueabdominal pain, one constipated stool/dayand 20 pound weight loss
CT scan shows pancreatic atrophy Lab tests
Serum carotene 50 mcg/dl (normal > 80)
72 hr fecal fat 28 g/day (normal < 7) 5 hr urinary D-xylose 7.5 g (normal > 4)
Whats the next step? Further testing? What test(s)? Treatment? With what?
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Case 2
36 yo man presents forevaluation of iron deficiencyanemia. No GI symptoms.No aspirin/NSAIDs.
IgA tTG antibody positive
Small bowel biopsy done
What result would you expecton the D-xylose test?
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Case 3
62 yo woman with h/o prior gastricsurgery (Roux-en-Y GJ) for PUD c/o
early satiety, diarrhea, foul-smellingbreath and weight loss
Whats the most likely diagnosis? What test(s) can confirm the diagnosis?
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Case 4
75 yo man presents with FUO, arthritis anddiarrhea
Labs show hypoproteinemia
Sprue antibodies negative
Negative SIBO breath test Small bowel biopsy done
What is the diagnosis?
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Case 5
22 yo man returns from a prolonged stay in thePhilippines c/o diarrhea, fatigue and 5 poundweight loss
Hgb 10.5 MCV 104
Folate low
D-xylose test decreased Celiac antibodies negative
Small bowel biopsy done
Whats the diagnosis? treatment?
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