eMedicine Specialties > Pediatrics: General Medicine > Gastroenterology

Lactose Intolerance: Differential Diagnoses & Workup

Author: Stefano Guandalini, MD, Director, University of Chicago Celiac Disease Program, Section Chief of Gastroenterology, Hepatology and Nutrition; Professor, Department of Pediatrics, University of Chicago Comer Children's Hospital
Coauthor(s): Richard E Frye, MD, PhD, Assistant Professor, Departments of Pediatrics and Neurology, University of Texas Health Science Center at Houston; Delia M Rivera, MD, Assistant Professor, Department of Pediatrics, Division of Infectious Disease and Immunology, University of Miami Leonard M Miller School of Medicine; Stephen Borowitz, MD, Professor of Pediatrics and Public Health Sciences, Department of Pediatrics, Division of Gastroenterology and Nutrition, University of Virginia
Contributor Information and Disclosures

Updated: Nov 13, 2008

Differential Diagnoses

Diarrhea
Malabsorption Syndromes
Protein Intolerance

Workup

Laboratory Studies

The following laboratory studies are indicated in patients with lactose intolerance:

  • Blood testing
    • The adult-type hypolactasia (most commonly caused by the CC genotype of the 13910 C/T polymorphism of the LCT gene) can now be easily diagnosed by a genetic analysis.
    • Studies have determined that genetic test results and breath test results are well-correlated, thereby eliminating the need for such testing.3  
  • Stool analysis
    • Reducing substances in the stool indicate that carbohydrates are not being absorbed. One common mistake, especially with super-absorbent diapers, is to test the solid portion of the stool instead of the liquid portion.
    • Acidic stool is defined by a pH level of less than 5.5. This is an indication of likely carbohydrate malabsorption, even in the absence of reducing substances.

Other Tests

  • Dietary elimination
    • Resolution of diarrhea and symptoms when a suspected substance is removed from the diet, as well as resumption of the diarrhea and symptoms when the substance is reintroduced, are very suggestive signs of intolerance.
    • Lack of diarrhea resolution when a substance is removed from the diet does not necessarily indicate tolerance. Malabsorption of one dietary component can result in diarrhea and subsequent malabsorption of other dietary components; thus, the sensitivity of this procedure can be low.
    • Conversely, resolution of symptoms upon withdrawal of lactose-containing foods from the diet may not confirm lactose intolerance. For instance, in the case of milk products, a patient can be sensitive to the milk proteins, and symptoms of such an allergy resolve once the milk or milk product is withdrawn from the diet.
  • Hydrogen breath test
    • Carbohydrate malabsorption results in bacterial fermentation of the unabsorbed sugar. This biochemical process releases hydrogen gas that is absorbed into the blood and excreted by the lungs. In the absence of hydrolysis of lactose into its component monosaccharide sugars, galactose and glucose, lactose cannot be absorbed and passes into the large intestine. Thus, carbohydrate malabsorption can be determined by measuring the exhaled hydrogen concentration after a carbohydrate load is administered.
    • Under normal conditions, the fermenting bacteria reside only in the large intestine. When bacterial overgrowth in the small intestine occurs, upper small bowel fermentation of ingested but nonhydrolyzed lactose occurs and causes an early rise in the exhaled hydrogen concentration (>20 ppm). Under such conditions, an additional later rise in exhaled hydrogen occurs during large bowel fermentation.
    • Antibiotic administration may cause false-negative results. For diagnosis of lactose intolerance, 0.5-1 g/kg to 12-25 g of lactose is administered.

Procedures

  • Mucosal biopsy is almost never needed to diagnose lactose intolerance. However, it may prove useful as a part of the workup in patients with malabsorption of obscure cause. A small intestinal mucosal biopsy sample is obtained via endoscopy for direct assay of lactase activity and other brush border disaccharidases.
  • The presence of small intestinal mucosal injury can also be assessed as a possible cause of secondary lactase deficiency.

Histologic Findings

  • No abnormal histologic findings in the small intestinal mucosa are present in adult-type lactose intolerance and the exceedingly rare primary lactase deficiency.
  • Villous blunting and lamina propria inflammatory changes are seen in cases of secondary lactase deficiency.

More on Lactose Intolerance

Overview: Lactose Intolerance
Differential Diagnoses & Workup: Lactose Intolerance
Treatment & Medication: Lactose Intolerance
Follow-up: Lactose Intolerance
References
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References

  1. Seppo L, Tuure T, Korpela R, et al. Can primary hypolactasia manifest itself after the age of 20 years? A two-decade follow-up study. Scand J Gastro. 2008;43:1082-1087. [Medline].

  2. Montalto M, Gallo A, Santoro L, et al. Low-dose lactose in drugs neither increases breath hydrogen excretion nor causes gastrointestinal symptoms. Aliment Pharmacol Ther. Oct 15 2008;28(8):1003-12. [Medline].

  3. Krawczyk M, Wolska M, Schwartz S, et al. Concordance of genetic and breath tests for lactose intolerance in a tertiary referral centre. J Gastrointestin Liver Dis. Jun 2008;17(2):135-9. [Medline].

  4. Griffin MP, Hansen JW. Can the elimination of lactose from formula improve feeding tolerance in premature infants?. J Pediatr. Nov 1999;135(5):587-92. [Medline].

  5. Bacsi K, Kosa JP, Lazary A, et al. LCT 13910 C/T polymorphism, serum calcium, and bone mineral density in postmenopausal women. Osteoporos Int. Aug 13 2008;[Medline].

  6. Bodlaj G, Stocher M, Hufnagl P, et al. Genotyping of the lactase-phlorizin hydrolase -13910 polymorphism by LightCycler PCR and implications for the diagnosis of lactose intolerance. Clin Chem. 2006;52:148-151. [Medline].

  7. Guandalini S. Treatment of acute diarrhea in the new millennium. J Pediatr Gastroenterol Nutr. 2000;30:486-9. [Medline].

  8. He T, Venema K, Priebe MG, Welling GW, Brummer RJ, Vonk RJ. The role of colonic metabolism in lactose intolerance. Eur J Clin Invest. Aug 2008;38(8):541-7. [Medline].

  9. Kuokkanen M, Kokkonen J, Enattah NS. Mutations in the Translated Region of the Lactase Gene (LCT) Underlie Congenital Lactase Deficiency. Am J Hum Genet. 2006;78:339-44. [Medline].

  10. Montalto M, Curigliano V, Santoro L. Management and treatment of lactose malabsorption. World J Gastroenterol. 2006;14:187-91. [Medline].

  11. Savaiano DA, Boushey CJ, McCabe GP. Lactose intolerance symptoms assessed by meta-analysis: a grain of truth that leads to exaggeration. J Nutr. 2006;136:1107-13. [Medline].

  12. Shulman RJ,, Wong WW, Smith EO. Influence of changes in lactase activity and small-intestinal mucosal growth on lactose digestion and absorption in preterm infants. Am J Clin Nutr. 2005;81:472-9. [Medline].

  13. Srinivasan R, Minocha A. When to suspect lactose intolerance. Symptomatic, ethnic, and laboratory clues. Postgrad Med. Sep 1998;104(3):109-11, 115-6, 122-3. [Medline].

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Further Reading

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Keywords

lactose intolerance, hypolactasia, lactase, milk intolerance, milk-protein allergy, milk protein allergy, primary lactase deficiency, congenital lactase deficiency, gastroenteritis, acute gastroenteritis, adult-onset lactase deficiency, glucose-galactose malabsorption, borborygmi, celiac disease, food allergy, diarrhea, infectious diarrhea, viral gastroenteritis

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Contributor Information and Disclosures

Author

Stefano Guandalini, MD, Director, University of Chicago Celiac Disease Program, Section Chief of Gastroenterology, Hepatology and Nutrition; Professor, Department of Pediatrics, University of Chicago Comer Children's Hospital
Stefano Guandalini, MD is a member of the following medical societies: American Gastroenterological Association, European Society for Paediatric Gastroenterology, Hepatology & Nutrition, and North American Society for Pediatric Gastroenterology and Nutrition
Disclosure: Nothing to disclose.

Coauthor(s)

Richard E Frye, MD, PhD, Assistant Professor, Departments of Pediatrics and Neurology, University of Texas Health Science Center at Houston
Richard E Frye, MD, PhD is a member of the following medical societies: American Academy of Neurology, American Academy of Pediatrics, Child Neurology Society, and International Neuropsychological Society
Disclosure: Nothing to disclose.

Delia M Rivera, MD, Assistant Professor, Department of Pediatrics, Division of Infectious Disease and Immunology, University of Miami Leonard M Miller School of Medicine
Delia M Rivera, MD is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, American Society for Microbiology, and Pediatric Infectious Diseases Society
Disclosure: Abbott Pharmaceuticals Honoraria Consulting; Monogram Biosciences Honoraria Consulting; Sanofi Pasteur: Combination Pediatric Vaccines Honoraria Speaking and teaching

Stephen Borowitz, MD, Professor of Pediatrics and Public Health Sciences, Department of Pediatrics, Division of Gastroenterology and Nutrition, University of Virginia
Stephen Borowitz, MD is a member of the following medical societies: American Academy of Pediatrics, American Gastroenterological Association, American Pediatric Society, North American Society for Pediatric Gastroenterology and Nutrition, and Society for Pediatric Research
Disclosure: Nothing to disclose.

Medical Editor

Alan D Schmetzer, MD, Professor and Vice-Chair for Education, Director of Residency Training, Department of Psychiatry, Indiana University School of Medicine
Alan D Schmetzer, MD is a member of the following medical societies: American Association for the Study of Liver Diseases, American Gastroenterological Association, American Society of Transplant Surgeons, and North American Society for Pediatric Gastroenterology and Nutrition
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from broker recommendation; Avanir Pharma Stock Investment from broker recommendation

Managing Editor

B U K Li, MD, Professor of Pediatrics, Division of Gastroenterology, Hepatology and Nutrition, Director, Pediatric Fellowships and Gastroenterology Fellowship, Medical Director, Functional Gastrointestinal Disorders and Cyclic Vomiting Program, Medical College of Wisconsin; Attending Gastroenterologist, Children's Hospital of Wisconsin
B U K Li, MD is a member of the following medical societies: Alpha Omega Alpha, American Gastroenterological Association, and North American Society for Pediatric Gastroenterology and Nutrition
Disclosure: Nothing to disclose.

CME Editor

Steven M Schwarz, MD, FAAP, FACN, AGAF, Professor of Pediatrics, State University of New York, Downstate Medical Center College of Medicine; Distinguished Lecturer, New York Medical College, School of Public Health
Steven M Schwarz, MD, FAAP, FACN, AGAF is a member of the following medical societies: American Academy of Pediatrics, American College of Nutrition, American College of Physician Executives, American Gastroenterological Association, American Pediatric Society, Gastroenterology Research Group, New York Academy of Medicine, North American Society for Pediatric Gastroenterology and Nutrition, and Society for Pediatric Research
Disclosure: TAP Pharmaceuticals Honoraria Speaking and teaching; Curemark, LLC Consulting fee Board membership

Chief Editor

Carmen Cuffari, MD, Associate Professor, Department of Pediatrics, Division of Gastroenterology/Nutrition, Johns Hopkins University School of Medicine
Carmen Cuffari, MD is a member of the following medical societies: American College of Gastroenterology, American Gastroenterological Association, North American Society for Pediatric Gastroenterology, Hepatology and Nutrition, and Royal College of Physicians and Surgeons of Canada
Disclosure: Nothing to disclose.

 
 
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