eMedicine Specialties > Pediatrics: General Medicine > Parasitology

Giardiasis: Differential Diagnoses & Workup

Author: Murat Hökelek, MD, PhD, Technical Consultant of Parasitology Laboratory, Associate Professor, Department of Clinical Microbiology, Ondokuz Mayis University Medical School, Turkey
Coauthor(s): Michael D Nissen, MBBS, BMedSc, FRACP, FRCPA, Associate Professor in Biomolecular, Biomedical Science & Health, Griffith University; Director of Infectious Diseases and Unit Head of Queensland Paediatric Infectious Laboratory, Sir Albert Sakzewski Viral Research Centre, Royal Children's Hospital
Contributor Information and Disclosures

Updated: Dec 17, 2008

Differential Diagnoses

Crohn Disease
Malabsorption Syndromes
Cryptosporidiosis
Sprue
Cyclosporiasis
Irritable Bowel Syndrome
Isosporiasis

Other Problems to Be Considered

Other etiologies of small-intestinal diarrhea (eg, bacterial gastroenteritis, strongyloidiasis, viral diarrhea)
Celiac disease19

Workup

Laboratory Studies

  • Stool examination for trophozoites or cysts is the traditional method for diagnosing giardiasis. Trophozoites may also be identified in the small intestine. Cysts are oval, measure 8-12 X 7-10 µm, and characteristically contain 4 nuclei. Trophozoites are pear-shaped, dorsally convex, flattened parasites with 2 nuclei and 4 pairs of flagella.17
    • Fresh and persevered stool samples should be examined.
    • Motile trophozoites are best identified in a saline wet mount of fresh liquid stool obtained during the acute stages of illness. Trophozoites are not usually found in semiformed stool.
    • Cysts are best detected in fresh stools after iodine staining or preservation in 10% buffered formalin or polyvinyl alcohol, with subsequent trichrome or iron hematoxylin staining.
    • Concentration techniques using formalin ether or zinc sulfate flotation may increase the yield.
    • Giardia intestinalis is identified in 50-70% of patients after a single stool examination and in more than 90% after 3 stool examinations.
    • In vitro culture is not routinely used because of the difficulty of reproducibly isolating Giardia from patient fecal samples
  • Antigen detection assays are available and often the tests of choice.28,3,29
    • Various immunologic techniques have been used to detect Giardia -specific antigens in fecal specimens. The most common technique is monoclonal antibody–based capture enzyme-linked immunosorbent assay (ELISA).
    • The antigen detection via ELISA is at least as sensitive as microscopic examination.
    • An immunofluorescence assay is available for detecting Giardia and Cryptosporidium species.
  • DNA probes for Giardia species are available. DNA-based fecal detection assays are being developed.30

Imaging Studies

  • Some patients with giardiasis have a nonspecific radiographic abnormality of the small intestine. These changes, which are reversible with therapy, include thickening and distortion of the mucosal folds of the duodenum and jejunum, hypersecretion, and hypermotility.7,28

Other Tests

  • Alternate methods to directly obtain duodenal fluid are the Entero-Test or duodenal biopsy17 .
    • For the Entero-Test (ie, string test), patients swallow a gelatin capsule on a string, and the capsule is left in the duodenum for several hours or overnight.
    • Biopsy can be used to obtain touch preparations and tissue sections to identify G intestinalis and other enteric pathogens.
    • Biopsy can also be used to visualize changes in histologic features.

Histologic Findings

Intestinal biopsy shows flattened, mild lymphocytic infiltration and trophozoites on the surface.12,19

  • Biopsy specimens from duodenum are often teeming with sickle-shaped Giardia trophozoites, which are tightly bound by the concave attachment disc to the villus surface of the intestinal epithelial cells.
  • Many patients exhibit atrophy of the small intestinal villi with a mixed inflammatory infiltrate in the lamina propria.
  • The brush borders of the surface absorptive epithelial cells are irregular, and virtual absence of villi may be noted, as in Celiac disease.

More on Giardiasis

Overview: Giardiasis
Differential Diagnoses & Workup: Giardiasis
Treatment & Medication: Giardiasis
Follow-up: Giardiasis
Multimedia: Giardiasis
References
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References

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Further Reading

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Keywords

giardiasis, Giardia, Giardia lamblia, Giardia duodenalis, Giardia intestinalis, protozoal diarrhea, steatorrhea, malabsorption, lambliasis, chronic diarrhea, vomiting, nausea, irritability, sleep disorder, mental depression, neuroasthenia, urticaria, abdominal cramps, contaminated food, food poisoning

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Contributor Information and Disclosures

Author

Murat Hökelek, MD, PhD, Technical Consultant of Parasitology Laboratory, Associate Professor, Department of Clinical Microbiology, Ondokuz Mayis University Medical School, Turkey
Murat Hökelek, MD, PhD is a member of the following medical societies: Turkish Society for Parasitology
Disclosure: Nothing to disclose.

Coauthor(s)

Michael D Nissen, MBBS, BMedSc, FRACP, FRCPA, Associate Professor in Biomolecular, Biomedical Science & Health, Griffith University; Director of Infectious Diseases and Unit Head of Queensland Paediatric Infectious Laboratory, Sir Albert Sakzewski Viral Research Centre, Royal Children's Hospital
Michael D Nissen, MBBS, BMedSc, FRACP, FRCPA is a member of the following medical societies: American Academy of Pediatrics, American Society for Microbiology, Pediatric Infectious Diseases Society, Royal Australasian College of Physicians, and Royal College of Pathologists of Australasia
Disclosure: Nothing to disclose.

Medical Editor

Glenn J Fennelly, MD, MPH, Director, Division of Pediatric Infectious Diseases, Jacobi Medical Center; Associate Professor, Department of Pediatrics, Albert Einstein College of Medicine
Glenn J Fennelly, MD, MPH is a member of the following medical societies: Pediatric Infectious Diseases Society
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 financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

Martin Weisse, MD, Program Director, Associate Professor, Department of Pediatrics, West Virginia University
Martin Weisse, MD is a member of the following medical societies: Ambulatory Pediatric Association, American Academy of Pediatrics, and Pediatric Infectious Diseases Society
Disclosure: Nothing to disclose.

CME Editor

Robert W Tolan Jr, MD, Chief, Division of Allergy, Immunology and Infectious Diseases, The Children's Hospital at Saint Peter's University Hospital; Clinical Associate Professor of Pediatrics, Drexel University College of Medicine
Robert W Tolan Jr, MD is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, American Society for Microbiology, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, Phi Beta Kappa, and Physicians for Social Responsibility
Disclosure: GlaxoSmithKline Honoraria Speaking and teaching; MedImmune Honoraria Consulting; MedImmune Honoraria Speaking and teaching; Merck Honoraria Speaking and teaching; Novartis Honoraria Speaking and teaching; sanofi pasteur Grant/research funds Unrestricted research grant; sanofi pasteur  Consulting; sanofi pasteur Honoraria Speaking and teaching; Tap Honoraria Speaking and teaching; Baxter Healthcare Honoraria Speaking and teaching

Chief Editor

Russell W Steele, MD, Head, Division of Pediatric Infectious Diseases, Ochsner Children's Health Center; Clinical Professor, Department of Pediatrics, Tulane University School of Medicine
Russell W Steele, MD is a member of the following medical societies: American Academy of Pediatrics, American Association of Immunologists, American Pediatric Society, American Society for Microbiology, Infectious Diseases Society of America, Louisiana State Medical Society, Pediatric Infectious Diseases Society, Society for Pediatric Research, and Southern Medical Association
Disclosure: None None None

 
 
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