Pediatric emergency medicine trisk 2321 2321
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GASTROINTESTINAL/GENITOURINARY
Amebiasis
Amebiasis, caused by the parasite E. histolytica, is responsible for approximately
55,000 deaths/yr globally; it is the third most frequently isolated pathogen
among returning travelers with infectious diarrhea. Amebiasis is transmitted via
fecal–oral contact with amebic cysts; humans are the only reservoir. High-risk
groups include foreign travelers, migrant workers, immunocompromised
individuals, children in daycare centers, and prisoners. Less than 20% of persons
who consume infected cysts develop symptoms. The spectrum of infection
ranges from asymptomatic carriers to intestinal amebiasis, hepatic abscesses, or
amebomas. Intestinal amebiasis typically has an insidious onset consisting of
weight loss, abdominal pain, and initially nonbloody progressing to dysentery.
Fever is rare. Complications include intestinal ulcers, fulminant colitis, and
perforation. Hepatic amebic abscesses present clinically as fever, cough,
tachypnea, hepatomegaly, and right upper quadrant pain with referred shoulder
pain (the latter is more common in adults). Liver abscesses are the most common
extraintestinal form of amebiasis. Rupture of the abscess with peritoneal seeding
can be fatal. While drainage may be adjunctive to medical therapy, percutaneous
drainage under controlled circumstances is optimal to prevent peritoneal seeding.
Other extraintestinal manifestations are rare, but may include pericardial,
pleuropulmonary, cerebral, genitourinary, and cutaneous amebiasis. Amebomas
are annular lesions of cecum or colon that can mimic cancer or pyogenic
abscesses. These usually can be managed medically.
Diagnosis is made via visualization of cysts or trophozoites in stool (for
colitis) or serum enzyme immunoassay (EIA) testing (for extraintestinal
disease). PCR can differentiate E. histolytica from related, nonpathogenic
species. CT can help identify extraintestinal manifestations. Ancillary testing
may reveal leukocytosis, anemia, or transaminitis. Treatment of asymptomatic
carriers is with paromomycin (25 to 35 mg/kg/day in three divided doses for 7
days) or diloxanide furoate (20 mg/kg/day in three divided doses [maximum:
500 mg/dose] for 10 days). Treatment of colitis is with metronidazole (35 to 50
mg/kg/day divided into three doses for 7 to 10 days; maximum: 750 mg/dose).
Treatment of liver abscesses, ameboma, or moderate/severe intestinal amebiasis
is with metronidazole and paromomycin. Surgical intervention may be needed
for patients with hepatic abscesses unresponsive to medical management or
those with toxic megacolon. Contact precautions are recommended.
