Rosen & Barkin's 5-Minute Emergency Medicine Consult (299 page)

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Authors: Jeffrey J. Schaider,Adam Z. Barkin,Roger M. Barkin,Philip Shayne,Richard E. Wolfe,Stephen R. Hayden,Peter Rosen

Tags: #Medical, #Emergency Medicine

BOOK: Rosen & Barkin's 5-Minute Emergency Medicine Consult
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  • Aortic Dissection, Thoracic
  • Central Retinal Artery Occlusion
  • Central Retinal Vein Occlusion
  • Glaucoma
  • Systemic Lupus erythematous
  • Vasculiits
CODES
ICD9

446.5 Giant cell arteritis

ICD10
  • M31.5 Giant cell arteritis with polymyalgia rheumatica
  • M31.6 Other giant cell arteritis
GIARDIASIS
Benjamin Mattingly

Joseph B. Schneider
BASICS
DESCRIPTION
  • Noninvasive diarrhea
  • Found worldwide:
    • 2–15% prevalence in developed nations
    • 20–40% prevalence in developing nations
  • 5% of all travelers’ diarrhea
  • Most common intestinal parasite in US:
    • Highest incidence in early summer months through fall
    • Highest incidence in children aged 1–9 yr and adults aged 30–39 yr
    • In 2010, 19,888 cases reported in US (mostly from Northern States)
  • Fecal–oral transmission:
    • Humans are major reservoir
    • Zoonotic reservoir in both domestic and wild mammals
    • Reservoir in contaminated surface water
  • Populations at risk:
    • Travelers to endemic areas (developing countries, wilderness areas of US)
    • Children in day care centers and their close contacts
    • Institutionalized persons
    • Practitioners of anal sexual activity
ETIOLOGY
  • Giardia lamblia:
    • A protozoan flagellate
  • Also called Giardia intestinalis or Giardia duodenalis
  • Ingested Giardia attach to intestinal villi
  • Alters the intestinal brush-border enzymes, impairing digestion of lactose, and other saccharides
  • No toxin produced
DIAGNOSIS
SIGNS AND SYMPTOMS
History
  • Onset 1–2 wk postexposure
  • Infection may be asymptomatic (most common).
  • Diarrhea of acute onset (90% of symptomatic patients):
    • Foul-smelling stools
    • Steatorrhea
    • Nonbloody
    • Self-limiting within 2–4 wk
    • More severe in immunocompromised patients and patients with underlying bowel disease
  • Flatulence and bloating (70–75%)
  • Abdominal cramping (70%)
  • Nausea (70%)
  • Vomiting (30%)
  • Malaise (86%)
  • Anorexia (66%)
  • Weight loss (60–70%)
  • Fever is rare (15%)
  • 30–50% of acute cases progress to chronic giardiasis (>4 wk):
    • Fat malabsorption
    • Severe macrocytic anemia secondary to folate deficiency
    • Secondary lactase deficiency (in 20–40% of patients)
  • Infection is more severe and harder to eradicate in immunosuppressed patients.
Pediatric Considerations
  • Acute infection:
    • Severe dehydration
  • Chronic infection:
    • Failure to thrive
    • Growth retardation and cognitive impairment owing to nutrient malabsorption
Physical-Exam
  • Abdominal exam is benign.
  • Extraintestinal manifestations (10% of patients):
    • Polyarthritis
    • Urticaria
    • Aphthous ulcers
    • Maculopapular rash
    • Biliary tract disease
ESSENTIAL WORKUP
  • History:
    • Possible sources of exposure
    • Membership in high-risk group
  • Physical exam:
    • If gross or occult blood on digital rectal exam, unlikely to be
      Giardia
DIAGNOSIS TESTS & NTERPRETATION
Lab
  • Stool sample for microscopy (ova and parasites):
    • 50–70% sensitive if 1 sample
    • 85–90% sensitive if 3 samples taken at 2-day intervals (ideal)
    • 100% specific
    • Ability to detect other parasites as well
  • Stool ELISA or immunofluorescent antibody (IFA) assay for
    Giardia
    antigen:
    • 95% sensitive, 95–100% specific
    • Unlike microscopy, cannot rule out other parasites
  • Stool polymerase chain reaction (PCR):
    • 100% sensitive and 100% specific
  • Fecal leukocytes and stool culture unnecessary unless enteroinvasive organisms suspected (fever, bloody stool)
  • Serology for anti-
    Giardia
    antibodies not helpful in the ED setting
  • Electrolytes, BUN/creatinine, glucose:
    • If prolonged diarrhea or evidence of dehydration
  • CBC:
    • Macrocytic anemia in chronic giardiasis
    • Nondiagnostic in acute giardiasis
Imaging

Abdominal CT or ultrasound may show bowel wall thickening and flattened duodenal folds (nonspecific findings)

Diagnostic Procedures/Surgery
  • Duodenal sampling:
    • Entero-Test (patient swallows a weighted string, which is later retrieved and examined for
      Giardia
      using microscopy)
  • Endoscopy:
    • Duodenal aspiration
    • Endoscopic duodenal biopsy
DIFFERENTIAL DIAGNOSIS
  • Viral gastroenteritis:
    • Norwalk virus
    • Rotavirus
    • Hepatitis A
  • Bacterial infections:
    • Staphylococcus
    • Escherichia coli
    • Shigella
    • Salmonella
    • Yersinia
    • Campylobacter
    • Clostridium difficile
    • Vibrio cholerae
  • Other protozoa:
    • Cryptosporidium
    • Microsporidia
    • Cyclospora
    • Isospora
    • Entamoeba
  • Inflammatory bowel disease
  • Irritable bowel syndrome
  • Lactase deficiency
  • Tropical sprue
  • Drugs and toxins:
    • Antibiotics
    • Calcium channel blockers
    • Magnesium antacids
    • Caffeine
    • Alcohol
    • Sorbitol
    • Laxative abuse
    • Quinidine
    • Colchicine
    • Mercury poisoning
  • Endocrine:
    • Addison disease
    • Thyroid disorders
  • Malignancy:
    • Colorectal carcinoma
    • Medullary carcinoma of the thyroid
TREATMENT
INITIAL STABILIZATION/THERAPY
  • ABCs: Airway, breathing, circulation
  • IV 0.9% NS if signs of significant dehydration
Pediatric Considerations
  • For severe dehydration (>10%):
    • IV bolus with 0.9% NS at 20 mL/kg
    • Cardiac monitor
    • Blood glucose determination
ED TREATMENT/PROCEDURES
  • Oral fluids for mild dehydration
  • Correct any serum electrolyte imbalances.
  • Stool sample for microscopy
  • If stool sample is positive for
    Giardia:
    Treat as listed below under medication
  • If stool sample negative for
    Giardia:
    • Refer to gastroenterologist for further specialized testing.
    • Consider empiric course of metronidazole if high suspicion for
      Giardia.
MEDICATION
First Line
  • Metronidazole or tinidazole are the treatment of choice:
    • 90% cure rate for each
  • Metronidazole: 250–500 mg (peds: 15 mg/kg/24h) PO q8h for 5–10 days
  • Tinidazole: 2 g (peds [>3 yr]: 50 mg/kg) PO once
Second Line

Albendazole (78–90% efficacy), quinacrine (90% efficacy), or nitazoxanide (75% efficacy) if 1st-line therapy fails

  • Albendazole: 400 mg (peds: 10–15 mg/kg/24h) PO daily for 5–7 days
  • Furazolidone: 100 mg (peds: 6–8 mg/kg/24h) PO q6h for 7–10 days (not available in US)
  • Nitazoxanide: 500 mg (peds: 100 mg for ages 2–3 yr, 200 mg for ages 4–11 yr) PO BID for 3 days
  • Paromomycin: 500 mg (peds: 25–30 mg/kg/24h) PO q8h for 5–10 days
  • Quinacrine: 100 mg (peds: 6 mg/kg/24h) PO q8h for 5–7 days (limited availability)
Pediatric Considerations
  • Metronidazole is 1st-line therapy (80–95% efficacy)
  • Alternatives:
    • Furazolidone (80–85% efficacy)
    • Nitazoxanide (60–80% efficacy)
    • Paromomycin (55–90% efficacy)

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