Clinical presentation and diagnosis

Clinical Presentation and Diagnosis of Amebiasis

Review of the patient's history should include: recent travel, type of foods ingested (e.g., salads or unpeeled fruit), the nature of water and fluid consumed, and description of any symptoms of friends or relatives who ate the same food.

Intestinal Disease

• Vague abdominal discomfort

• Symptoms may range from malaise to severe abdominal cramps, flatulence, and nonbloody or bloody diarrhea (heme-positive in 100% of cases) with mucus

• May have low-grade fever, but this may be absent in many patients

• Eosinophilia is usually absent, although mild leukocytosis is not unusual

Note: Fecal screening may show other intestinal parasites, including Cryptosporidium spp., Balantidium coli, Dientamoeba fragilis, Isospora belli, G. lamblia, or Blastocystis hominis.

Amebic Liver Abscess

• May present with high fever with significant leukocytosis with left shift, anemia, elevated alanine aminotransferase, and dull abdominal pain on palpation

• Physical findings: Right upper quadrant pain, hepatomegaly, and liver tenderness, with referred pain to the left or right shoulder (Note: Erosion of liver abscesses may present as peritonitis.)


• Intestinal amebiasis is diagnosed by demonstrating E. histolytica cysts or trophozoites (may contain ingested erythrocytes) in fresh stool or from a specimen obtained by sigmoidoscopy.

• Microscopy may not differentiate between the pathogenic E. histolytica and the nonpathogenic E. dispar or E. moshkovskii in stools.

• Sensitive techniques are available to detect E. histolytica in stool: antigen detection, antibody test (ELISA) and PCR.

• Endoscopy with scrapings or biopsy and stained slides (iron hematoxylin or tri-chrome) may provide more definitive diagnosis of amebiasis.

• Diagnosis for liver abscess includes serology and liver scans (using isotopes by ultrasound or CT) or MRI; however, none of these are specific for liver abscess. In rare instances, needle aspiration of hepatic abscess may be attempted using ultrasound guidance.

Patients with severe intestinal disease or liver abscess should receive metronidazole

750 mg three times daily for 10 days, followed by the luminal agents indicated above.

The pediatric dose of metronidazole is 50 mg/kg/day in divided doses, which should be followed by a luminal agent. An alternative regimen of metronidazole is 2.4 g/day

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for 2 days in combination with the luminal agent. ' Tinidazole (Tindamax, recently introduced in the U.S. market) administered in a dose of 2 g daily for 3 days (pediatric dose: 50 mg/kg for 3 days) is an alternative to metronidazole. If there is no prompt response to metronidazole or aspiration of the abscess, an antibiotic regimen should be added. Patients who cannot tolerate oral doses of metronidazole should receive an equivalent dose IV.

Patient Encounter 2: Amebiasis

WR is a 37-year-old native of India and a permanent resident in the United States who has recently returned from a trip to Calcutta where he was visiting a relative. He presents in the emergency department with complaints of a 3-week history of sharp, crampy, and postprandial abdominal pain. The pain is more intense over the right lower quadrant and associated with watery nonbloody diarrhea and tenesmus.

What specific findings in this patient suggest that he may have giardiasis or amebiasis?

What other information do you need to confirm a diagnosis of amebiasis? What is the major complication of amebiasis?

Patient Care and Monitoring: Amebiasis

1. Follow-up in patients with amebiasis should include repeat stools (1-3), colono-scopy (in colitis) or CT (in liver abscess) between days 5 and 7, at the end of the course of therapy, and a month after the end of therapy.

2. Most patients with either intestinal amebiasis or colitis will respond in 3 to 5 days with amelioration of symptoms.

3. Those with liver abscess may take up to 7 days before there will be decreases in pain and fever. In liver abscess, patients not responding by the fifth day may require aspiration of the abscesses or exploratory laparotomy.

4. Serial liver scans have demonstrated that healing of liver abscesses take from 4 to 8 months following adequate therapy.

Preventive Measures

• Travelers and tourists visiting endemic areas should avoid local tap water, ice, salads, and unpeeled fruits. Boiled water is safe.

• Water can be disinfected by the use of iodine 2% (5 drops/L) or chlorine 6% (laundry bleach: 4 drops/L) or use of a commercial water purifier, such as Portable Aqua tablets (Wisconsin Pharmaceutical).

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