Giardiasis

Giardiasis
Diagnosis in short
Giardiasis. H&E stain.
LM	flagellate protozoa - pale/transluence on H&E, 12-15 micrometers (long axis) x 6-10 micrometers (short axis); +/-loss of villi, intraepithelial lymphocytes, inflammatory cells - especially close to the luminal surface
LM DDx	celiac disease
Stains	methylene blue +ve
IHC	CD117 +ve (microorganisms)
Site	duodenum
Signs	diarrhea x5 days, foul smelling feces, flatulence
Symptoms	fatigue, abdominal cramps, nausea
Prevalence	uncommon
Endoscopy	+/-white spots, diffuse changes
Prognosis	good, benign
Clin. DDx	celiac disease, other causes of diarrhea
Treatment	antibiotics

Giardiasis is a rare infection, classically found in the duodenum. It can mimic celiac disease. It is also known as beaver fever.

General

Clinical features - usually two or more of the following:

• Diarrhea - x5 days.
• Flatulence.
• Foul smelling feces.
• Nausea.
• Abdominal cramps.
• Excessive tiredness.

Epidemiology:

• Uncommon.

Etiology:

• Flagellate protozoan Giardia lamblia.

Treatment

• Antibiotics, e.g. metronidazole (Flagyl).

Gross

• Diffuse changes.
• May have scattered white spots.

Microscopic

Features:

• +/-Loss of villi.
• Intraepithelial lymphocytes.
  • +Other inflammatory cells, especially PMNs, close to the luminal surface.
• Flagellate protozoa -- diagnostic feature.
  • Organisms often at site of bad inflammation.
  • Pale/translucent on H&E.
  • Size: 12-15 micrometers (long axis) x 6-10 micrometers (short axis) -- if seen completely.
    • Often look like a crescent moon (image of crescent moon) or semicircular -- as the long axis of the organism is rarely in the plane of the (histologic) section.

Note:

• Changes are typically diffuse, i.e. if multiple biopsies are done the changes are present in all fragments.

DDx:

• Celiac disease - near perfect mimic; missing giardia organisms.

Images

Case 1

• 

  Giardiasis - high mag. (WC)

• 

  Giardiasis - low mag. (WC)

Case 2

• 

  Giardia - low mag.

• 

  Giardia - intermed. mag.

• 

  Giardia - high mag.

• 

  Giardia - high mag.

• 

  Giardia - very high mag.

www

• Giardiasis - several images (upmc.edu).

Stains

• Methylene blue +ve.

IHC

• CD117 +ve.

Sign out

A. Duodenum, Biopsy:
- Abundant micro-organisms consistent with GIARDIA and small 
  bowel mucosa with increased intraepithelial lymphocytes, see comment.
- NEGATIVE for dysplasia.

B. Stomach, Biopsy:
- Body and antral-type mucosa with mild chronic inactive inflammation.
- NEGATIVE for Helicobacter-like organisms.
- NEGATIVE for intestinal metaplasia.
- NEGATIVE for dysplasia and NEGATIVE for malignancy.

Comment:
The increased intraepithelial lymphocytes are likely to due to the Giardia; however, other 
causes cannot be excluded.

Block letters

DUODENUM, BIOPSY:
- SMALL BOWEL MUCOSA WITH BRUNNER'S GLANDS AND MICROORGANISMS CONSISTENT WITH GIARDIA.

See also

• Duodenum.