Malabsorption A Clinical Approach

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?

Documents

Malabsorption A Clinical Approach