Malabsorption

Indications for Testing

Diarrhea, steatorrhea, or preexisting condition that may predispose to malabsorption

Laboratory Testing

Initial screening tests
- CBC
  - Mild anemia frequent; leukocytosis in IBD or infectious etiology
  - Eosinophilia – consider parasitic evaluation
- Electrolyte panel
- ESR – elevated in inflammatory or infectious processes
- Liver enzymes, including albumin – low albumin suggests chronic processes
- TSH – rule out thyroid disease
- In children and adolescents – cystic fibrosis testing (sweat chloride)
- Fecal tests – perform in parallel with serum tests
  - Stool culture, ova and parasite – rule out infectious diarrhea (bacterial, viral, parasitic); C. difficile testing if risk factors present
  - Fecal leukocytes – present in IBD, infectious diarrhea
  - Fecal occult blood or guaiac
  - Fecal fat, qualitative/quantitative
- Consider celiac serologies (tTG antibody testing with IgA level)
- If initial test results are abnormal, proceed to testing based on suspected disease (see the Malabsorption Testing Algorithm)
Secondary testing – hydrogen breath test; serum or urine D-xylose; vitamins A, D, E, B₁₂; pancreatic enzyme analysis

Imaging Studies

If initial test results are normal, consider abdominal CT or ultrasound, endoscopy

Differential Diagnosis

See causes of malabsorption in Clinical Background

Malabsorption is characterized by the inability to digest or absorb nutrients from the small intestine into the bloodstream and is related to diseases of the pancreas, liver, and intestine.

Causes of Malabsorption

Inadequate digestion of nutrients
- Deficiencies of pancreatic enzymes (eg, chronic pancreatitis, pancreatic carcinoma, cystic fibrosis)
- Impaired synthesis or secretion of bile (eg, biliary obstruction, cirrhosis)
- Deconjugation of bile salts (eg, blind-loop syndrome)
Inadequate absorption of nutrients
- Shortened bowel or loss of absorptive surface (eg, inflammatory bowel disease [IBD], including ulcerative colitis, Crohn disease, gluten-sensitive enteropathy [Celiac sprue], tropical sprue, lymphoma, surgical loss of functional bowel, blind-loop syndrome, hormonal disorders)
- Impaired nutrient metabolism (eg, deficiency of intestinal disaccharidases, lactase deficiency)
- Nutrient-specific transport deficiencies (eg, Hartnup disease)
- Decreased availability of specific nutrients (eg, vitamin B₁₂ deficiency due to decreased intrinsic factor)
- Alterations of circulation (eg, mesenteric ischemia, heart failure, portal hypertension, lymphatic obstruction
Miscellaneous
- Amyloidosis, systemic sclerosis (scleroderma), hyperthyroidism, Zollinger-Ellison syndrome, atrophic gastritis, medication-induced malabsorption, neurofibromatosis

Pathophysiology

Nutrient digestion and absorption occurs in three phases
- Luminal phase – breakdown and solubilization of proteins, carbohydrates, and fats by digestive enzymes and bile
- Mucosal phase – transport of digested nutrients into gastrointestinal epithelial cells
- Transport phase – transport of nutrients via lymphatics and portal circulation from small intestine to other parts of the body
Any process that disrupts one or more of these phases can cause malabsorption

Clinical Presentation

Prominent symptom – diarrhea
Constitutional – weight loss, fatigue
Gastrointestinal – steatorrhea, abdominal bloating, abdominal pain, somatostatinoma
Extraintestinal – anemia, skin rashes, stomatitis, glossitis, peripheral edema, ascites

Tests generally appear in the order most useful for common clinical situations

Test name: CBC with Platelet Count

ARUP #: 0040002

Methodology: Automated Cell Count

Use:

Assess for presence of anemia and leukocytosis

Test name: Electrolyte Panel

ARUP #: 0020410

Methodology: Quantitative Ion-Selective Electrode/Enzymatic

Use:

Assess for inflammatory processes

Test name: Sedimentation Rate, Westergren (ESR)

ARUP #: 0040325

Methodology: Westergren

Use:

Assess for inflammatory processes

Elevated in inflammatory or infectious processes

Test name: Aspartate Aminotransferase, Serum or Plasma

ARUP #: 0020007

Methodology: Quantitative Enzymatic

Use:

Screen for other causes of malabsorption

Test name: Alanine Aminotransferase, Serum or Plasma

ARUP #: 0020008

Methodology: Quantitative Enzymatic

Use:

Screen for other causes of malabsorption

Test name: Albumin, Serum by Nephelometry

ARUP #: 0050671

Methodology: Quantitative Nephelometry

Use:

Assess nutritional status

Low albumin suggestive of chronic process

Test name: Thyroid Stimulating Hormone

ARUP #: 0070145

Methodology: Quantitative Electrochemiluminescent Immunoassay

Use:

Rule out thyroid disease as cause for malabsorption

Test name: Occult Blood, Fecal

ARUP #: 0020374

Methodology: Qualitative Colorimetry

Use:

Assess for fecal blood

Test name: Lactoferrin, Fecal by ELISA

ARUP #: 0061164

Methodology: Qualitative Enzyme-Linked Immunosorbent Assay

Use:

Assess bowel inflammation

Determine presence of fecal leukocytes

Test name: Fat, Fecal Qualitative

ARUP #: 0020385

Methodology: Qualitative Microscopic/Stain/Heat

Use:

Determine presence of steatorrhea

Determine etiology of malabsorption

Increased neutral fats suggest a deficiency of pancreatic enzymes; increased split fats suggest impaired bile secretion or inadequate absorption of nutrients

Include as part of metabolic or fat balance studies

Limitations:

Results can not be used if patient on low fat diet

Test name: Fat, Fecal Quantitative, Homogenized Aliquot

ARUP #: 2002350

Methodology: Nuclear Magnetic Resonance Spectroscopy

Use:

Definitive test for determining the presence of malabsorption

Include as part of metabolic or fat balance studies

Limitations:

Results cannot be used if patient on low-fat diet

Quantitative test requires a 72-hour stool collection

Follow-up:

If increased, consider xylose absorption test for assessment of intestinal mucosa integrity

Test name: Ova & Parasite Exam, Fecal (Immunocompromised or Travel History)

ARUP #: 2002272

Methodology: Qualitative Concentration Technique/Trichrome Stain/Microscopic Evaluation

Use:

Rule out parasites as cause for malabsorption in immunocompromised patients and patients with appropriate travel history

Limitations:

Stool antigen testing is the optimal test method for determining the parasitic presence of Giardia duodenalis(synonyms Giardia lamblia, Giardia intestinalis), Cryptosporidium spp, or Entamoeba histolytica

The ova and parasite exam does not specifically detect Cryptosporidium, Cyclospora, Isospora, and Microsporidia; for Cryptosporidium, refer to the Cryptosporidium Antigen by EIA test; for Cyclospora and Isospora, refer to Parasitology Stain by Modified Acid-Fast; for Microsporidia, refer to Microsporidia Stain

Test name: Celiac Disease Reflexive Panel

ARUP #: 0051065

Methodology: Quantitative Nephelometry/Semi-Quantitative Enzyme-Linked Immunosorbent Assay

Use:

Rule out celiac disease

Test name: Immunoglobulin A

ARUP #: 0050340

Methodology: Quantitative Nephelometry

Use:

Rule out celiac disease

Test name: Tissue Transglutaminase Antibody, IgG

ARUP #: 0056009

Methodology: Semi-Quantitative Enzyme-Linked Immunosorbent Assay

Use:

Rule out celiac disease

Test name: Pancreatic Elastase, Fecal

ARUP #: 0080526

Methodology: Quantitative Enzyme-Linked Immunosorbent Assay

Use:

Evaluate exocrine pancreatic function

Determine etiology of pancreatic insufficiency

Sensitive and specific test for pancreatic insufficiency

Follow-up:

If pancreatic insufficiency is present, consider cystic fibrosis testing

Test name: Xylose Absorption Test (Adult - 5g dose)

ARUP #: 0020615

Methodology: Quantitative Spectrophotometry

Use:

Evaluate carbohydrate absorption by the mucosa of the proximal small intestine

5g dose is preferred in patients who do not tolerate the 25g dose

Test name: Xylose Absorption Test (Adult - 25g dose)

ARUP #: 0020609

Methodology: Quantitative Spectrophotometry

Use:

Evaluate carbohydrate absorption by the mucosa of the proximal small intestine

Decreased absorption of D-xylose is due to impaired intestinal absorption

Test name: Xylose Absorption Test (Child)

ARUP #: 0020612

Methodology: Quantitative Spectrophotometry

Use:

Evaluate carbohydrate absorption by the mucosa of the proximal small intestine

Test name: Lactose Tolerance

ARUP #: 0020407

Methodology: Quantitative Enzymatic

Use:

Evaluate mucosal absorption efficiency in a variety of malabsorptive diseases in children

May be used for diagnosing lactose deficiency

Components include fasting glucose, 30-minute glucose, 1-hour glucose, 2-hour glucose-LACTOL, 3-hour glucose

Additional Tests Available

Test name: Disaccharidase, Tissue

ARUP #: 2002247

Methodology: Quantitative Spectrophotometry

Comments:

Evaluate patients suffering with chronic diarrhea, intestinal upset, or failure to thrive

Test name: Fat, Fecal Quantitative 24-Hour Collection (Includes Homogenization)

ARUP #: 2002354

Methodology: Nuclear Magnetic Resonance Spectroscopy

Comments:

Test name: Fat, Fecal Quantitative 48-Hour Collection (Includes Homogenization)

ARUP #: 2002355

Methodology: Nuclear Magnetic Resonance Spectroscopy

Comments:

Test name: Osmolality, Fecal

ARUP #: 0098122

Methodology: Quantitative Freezing Point Depression

Comments:

Test name: Fat, Fecal Quantitative 72-Hour Collection (Includes Homogenization)

ARUP #: 2002356

Methodology: Nuclear Magnetic Resonance Spectroscopy

Comments:

Test name: Carotenes, Fractionated, Plasma or Serum

ARUP #: 0021021

Methodology: Quantitative High Performance Liquid Chromatography

Comments:

Test name: Electrolytes, Fecal

ARUP #: 0060185

Methodology: Quantitative Ion-Selective Electrode

Comments:

Test name: pH, Fecal

ARUP #: 0020518

Methodology: Quantitative pH Indicator Strips or pH meter

Comments:

Test name: Reducing Substances, Fecal

ARUP #: 0020373

Methodology: Semi-quantitative Colorimetry

Comments:

Test name: Trypsin-Like Immunoreactivity

ARUP #: 0070003

Methodology: Quantitative Radioimmunoassay

Comments:

Results should be correlated with clinical presentation and other diagnostic data for the diagnosis of pancreatitis

Test name: Carotene, Serum Total

ARUP #: 0080055

Methodology: Quantitative Spectrophotometry

Comments:

Test name: Hepatic Function Panel

ARUP #: 0020416

Methodology: Refer to individual components.

Comments:

Initial screening test for hepatobiliary problems

Panel includes albumin; ALP; AST; ALT; bilirubin, direct; protein, total; and bilirubin, total

Test name: Vitamin A (Retinol), Serum or Plasma

ARUP #: 0080525

Methodology: Quantitative High Performance Liquid Chromatography

Comments:

Test name: Vitamin D, 25-Hydroxy

ARUP #: 0080379

Methodology: Quantitative Chemiluminescent Immunoassay

Comments:

Test name: Vitamin E, Serum or Plasma

ARUP #: 0080521

Methodology: Quantitative High Performance Liquid Chromatography

Comments:

Test name: Vitamin B₁₂

ARUP #: 0070150

Methodology: Quantitative Chemiluminescent Immunoassay

Comments:

Test name: Clostridium difficile toxin B gene (tcdB) by PCR

ARUP #: 2002838

Methodology: Qualitative Polymerase Chain Reaction

Comments:

General

ARUP Institute for Clinical and Experimental Pathology®

Erickson JA, Aldeen WE, Grenache DG, Ashwood ER. Evaluation of a fecal pancreatic elastase-1 enzyme-linked immunosorbent assay: Assessment versus an established assay and implication in classifying pancreatic function. Clin Chim Acta. 2008; 397 (1-2) :87-91.PubMed

Comprehensive Review: November 2011
Last Update: November 2011

Anemia

Celiac Disease

Cystic Fibrosis

Diarrhea, Bacterial Evaluation

Diarrhea, Parasitic Evaluation

Diarrhea, Viral Evaluation

Inflammatory Bowel Disease

Vasoactive Intestinal Polypeptide Secreting Tumor

Vitamins

Zollinger-Ellison Syndrome