AMEBIC LIVER ABSCESS
Section snippets
PATHOGENESIS
Amebiasis is caused by ingestion of infective E. histolytica cysts through a fecal-oral route of exposure. Humans are the principal host, and the main source of infection is the cyst-passing chronic patient or asymptomatic carrier.92 The infective cysts reach humans through water and vegetables contaminated with feces, through food contaminated by night soil fertilizers or by hands of infected food handlers, or by direct transmission of cyst.92 A recent outbreak of amebiasis in the Republic of
EPIDEMIOLOGY
Amebiasis remains an important clinical problem in both developing and developed countries with a significant mortality rate even now.95 The disease is most prevalent in tropical and developing countries where sanitation, public health, and personal hygiene are suboptimal.6 Immigration and travel between countries, however, may increase the incidence of disease worldwide. Countries with the highest E. histolytica endemic activity include Mexico, India, East and South Africa, and portions of
Clinical Signs and Symptoms
Approximately 80% of patients with amebic liver abscess present with symptoms that develop over a few days to several weeks but typically less than 2 to 4 weeks in duration.11, 21, 29 The diagnosis of amebic liver abscess is suggested by the typical clinical picture of fever and chills, anorexia, right upper quadrant pain and tenderness, and hepatomegaly.54 The most common clinical signs and symptoms are listed in Table 2 and include fever, chills, nausea, weakness, and malaise, and a constant,
History and Physical Examination
A careful history must include the patient's presenting complaints, duration of illness, medical history, travel history, history of residence in an endemic area, ill contacts, HIV risk factors, evidence of malnutrition or immunosuppression, medications, and history of alcohol use. On physical examination, typical findings include a tired- and ill-appearing febrile patient with abdominal pain and tenderness usually in the right upper quadrant or epigastrium, hepatomegaly with liver span greater
Drug Therapy
Treatment options for uncomplicated amebic liver abscess include amebicidal drugs and, if indicated, percutaneous or open aspiration of the abscess.6 Metronidazole remains the drug of choice for treating amebic liver abscess.6, 24, 48 This drug has been used in clinical practice for over 25 years for the treatment of amebiasis.24, 93 Metronidazole is a nitroimidazole, which enters the parasite by passive diffusion where it is then converted to reactive cytotoxic nitro radicals by reduced
COMPLICATIONS OF AMEBIC LIVER ABSCESS
The most common complications from amebic liver abscess arise from rupture of abscess with extension into the peritoneum, pleural cavity, or pericardium.2, 28, 29, 41, 47 Peritonitis, paralytic ileus, fulminant colitis, colonic perforation, or toxic megacolon can occur as gastrointestinal complications of an amebic liver abscess.3 Depending on the size and location of the abscess, compression of the biliary tree can occur with resultant obstructive jaundice.3 In rare cases, inferior vena caval
LONG-TERM OUTCOME
In most cases, rapid clinical improvement is seen with antiamebic drug therapy alone within a few days to a week as measured by disappearance of fever, pain, and anorexia, greater than 50% regression in liver span on percussion, and normal leukocyte count.77, 78 In contrast, although the liver abscess eventually resolves with complete disappearance radiologically, it does not disappear rapidly on imaging studies. On average, time to complete radiologic resolution is 3 to 9 months, with a range
PREVENTION
Amebiasis infection can be prevented by interrupting the fecal-oral spread of infection, primarily by eradicating fecal contamination of food and water.58, 92 Fresh vegetables are the most commonly contaminated food sources and should be washed carefully with a detergent and then soaked in acetic acid or vinegar for 10 to 15 minutes to eradicate the infective cysts.92 Contaminated water is one of the most important sources for acquisition and spread of infection.12, 92 Boiling water before use
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Address reprint requests to Molly A. Hughes, MD, PhD, University of Virginia Health Sciences Center, Division of Infectious Diseases, MR4 Bldg., Box 2115, 300 Park Place, Charlottesville, VA 22908, e-mail: [email protected]
This work was supported by the National Institutes of Health, grant no. AI-43596.
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Division of Infectious Diseases, Department of Medicine, University of Virginia Health Sciences Center, Charlottesville, Virginia