Pathophysiology
infestation of small bowel with Giardia lamblia (G. intestinalis)
Signs and Symptoms
1) foul-smelling diarrhea 2) abdominal pain and cramps 3) bloating 4) nausea and vomiting 5) sulfurous burping 6) failure to thrive and weight loss in children 7) variable clinic course from asymptomatic infection to resolving over 2-4 weeks spontaneously to chronic infection
Histology/Gross Pathology
1) flagellated protozoan 2) cysts are ingested and then rupture to release the trophozoite form that attaches via ventral suckers to duodenum and proximal small bowel 3) trophozoites then reform cysts that are passed via feces 4) usually mucosa is not affected by trophozoites but in chronic cases can have some flattening of villi
Associated Conditions
1) lactose intolerance 2) malabsorption 3) urticaria 4) arthritis 5) anterior uveitis
Inheritance/Epidemiology
1) worldwide distribution 2) spread through oral/fecal route 3) common in daycare centers 4) common in populations that drink untreated stream and lake water (campers, rural population) 5) disease results from ingestion of as few as 10 cysts
Treatment
1) metronidazole 2) furazolidone in children
Tips for USMLE
if a 24 year-old man drank from a mountain spring on a camping trip two weeks ago and now has a “rotten egg” smell when he burps and five bowel movements a day of foul-smelling stools, think giardiasis
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