Comments
INITIAL SYMPTOMS:
1.) Mild: intermittent diarrhea with bloody mucous; 2.) Severe (more common in young children, pregnant women, and patients taking glucocorticoids): fever and chills with severe bloody diarrhea; 3.) Liver abscess; [Harrison, p. 549]
FINDINGS
Most infected patients have no symptoms but pass cysts in their feces. Patients with amebic dysentery may have mild symptoms or high fever with abdominal cramping. Tender hepatomegaly is common, and patients may also have anemia, weight loss, and amebomas (tumor-like masses of the colon). The organisms may invade any organ, but liver abscesses are the most common complication. [Merck Manual, p. 1368] Patients with amebic dysentery have fever, diarrhea, and blood in the stools. Complications include amebomas, liver abscesses, and rarely, lung and brain abscesses. [CCDM, p. 3] Only a minority of patients with amebic dysentery have fever. [Cecil, p. 2045] Chronic amebic dysentery mimics idiopathic inflammatory bowel disease. [Cohen, p. 397] Patients with liver abscesses may have right-sided pleural effusions and typically do not have active colitis. Jaundice is unusual. Patients with liver abscesses may have leukocytosis, mild anemia, elevated alkaline phosphatase, and elevated sedimentation rate. Headache, vomiting, and seizures are symptoms of a cerebral abscess. [Harrison ID, p. 1146-7] May cause jaundice if bile ducts are compressed by abscess; [Cohen, p. 1086] Cutaneous amebiasis is rare--nodules and ulcers of mucous membranes and perianal granulation tissue. [Guerrant, p. 963]
LABORATORY
The laboratory may fail to detect pus in stool specimens because the trophozoites lyse leukocytes. Lactoferrin tests can detect inflammatory diarrhea in such cases when fecal leukocytes are absent. [PPID 7th Ed., p. 1345] In liver abscesses, leukocytosis and elevated transaminases and alkaline phosphatase are common. [Cohen, p. 1149] A patient with radiological evidence of at least one space-occupying lesion in the liver and a positive serology can be considered a confirmed case of amebic liver abscess. Amebic liver abscesses are treated with antibiotics, and drainage is rarely needed. [Harrison, p. 549] The different strains (E. histolytica, E. dispar, and E. moshkovskii) cannot be distinguished microscopically. New evidence suggests that E. moshkovskii may also be pathogenic. E. histolytica can be identified by EIA and PCR tests. [CDC Travel, p. 139-40]
EPIDEMIOLOGY
Incidence of infection is high in developing countries, among travelers, and in recent immigrants. Cysts are present in fecally contaminated water and food, and on hands. Cysts can survive for weeks in moist environments. [Harrison, p. 548] Positive serology surveys found rates of 8.4% for Mexico, 25% for urban slum dwellers in Fortaleza (Brazil), and 40% for children 6-14 years old living in Dhaka, Bangladesh. [Cecil, p. 2043] Families with poor sanitation are at increased risk for E. histolytica infection. Transmission occurs by ingestion of water or food contaminated with feces containing cysts, which are relatively resistant to chlorine water treatment. [CCDM, p. 4-5] Liver abscesses may occur years after travel or residence in an endemic country. Institutionalized populations and men who have sex with men are at increased risk of acquiring infection. AIDS patients do not have increased risk. [Harrison ID, p. 1145-7]
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