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

• Aortic Dissection, Thoracic
  
• Central Retinal Artery Occlusion
  
• Central Retinal Vein Occlusion
  
• Glaucoma
  
• Systemic Lupus erythematous
  
• Vasculiits
  

CODES

446.5 Giant cell arteritis

BASICS

• 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
    

• 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

• 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.
  

• Acute infection:
  
  • Severe dehydration
    
• Chronic infection:
  
  • Failure to thrive
    
  • Growth retardation and cognitive impairment owing to nutrient malabsorption
    

• Abdominal exam is benign.
  
• Extraintestinal manifestations (10% of patients):
  
  • Polyarthritis
    
  • Urticaria
    
  • Aphthous ulcers
    
  • Maculopapular rash
    
  • Biliary tract disease
    

• 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
    

• 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
    

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

• 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
    

• 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

• ABCs: Airway, breathing, circulation
  
• IV 0.9% NS if signs of significant dehydration
  

• For severe dehydration (>10%):
  
  • IV bolus with 0.9% NS at 20 mL/kg
    
  • Cardiac monitor
    
  • Blood glucose determination
    

• 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.
    

• 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
  

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)
  

• Metronidazole is 1st-line therapy (80–95% efficacy)
  
• Alternatives:
  
  • Furazolidone (80–85% efficacy)
    
  • Nitazoxanide (60–80% efficacy)
    
  • Paromomycin (55–90% efficacy)