MKSAP quiz: Treatment of amebic liver abscess

This month's quiz asks readers to determine the most appropriate treatment for a 46-year-old man with an amebic liver abscess.

A 46-year-old man is evaluated for abdominal pain in the right upper quadrant and fever of 1 month's duration. He recently emigrated from Mexico. His medical history is unremarkable, and he takes no medication.

On physical examination, temperature is 37.7 °C (99.9 °F); other vital signs are normal. Abdominal examination shows tenderness to palpation of the right upper quadrant. No scleral icterus is noted. The remainder of the examination is normal.

An ultrasound of the liver shows a fluid-containing structure and complex wall consistent with hepatic abscess.

Laboratory studies show a leukocyte count of 10,600/µL (10.6 × 109/L). Testing for Entamoeba histolytica IgG is positive.

Which of the following is the most appropriate treatment?

A. Meropenem
B. Metronidazole and paromomycin
C. Percutaneous drainage of the abscess
D. Surgical resection

MKSAP Answer and Critique

The correct answer is B. Metronidazole and paromomycin. This content is available to MKSAP 18 subscribers as Question 53 in the Gastroenterology and Hepatology section. More information about MKSAP is available online.

Metronidazole plus paromomycin is the most appropriate treatment for this patient with an amebic liver abscess. The two most common types of hepatic abscess are pyogenic and amebic. Pyogenic liver abscesses are the most common hepatic abscesses in the United States, whereas amebic abscesses are seen more frequently in the developing world. Pyogenic abscesses are typically polymicrobial, originating from gastrointestinal flora in the setting of intra-abdominal infections, malignancies, or procedures. Amebic abscesses are usually caused by the organism Entamoeba histolytica, and the mechanism of formation involves enteric infection with the invasion of amoeba through the intestinal mucosa and via the portal vein. With amebic abscesses, infection of the liver is asymptomatic until hepatic necrosis results in abscess development, at which time abdominal pain, fever, and leukocytosis develop. Amebic liver abscesses are seen in patients from endemic areas, such as India, Africa, or Central or South America, or in patients who have traveled to endemic areas. The typical presentation in travelers occurs 3 to 5 months after infection. Nearly all patients with an amebic abscess have positive serological studies for E. histolytica. The diagnosis is usually established with compatible imaging and serologic testing. Ultrasonography is less sensitive for the detection of pyogenic liver abscesses (CT is preferred) but may be equally sensitive for the detection of amebic abscesses. The mainstay of therapy for an amebic liver abscess is antibiotic therapy, such as metronidazole, plus a luminal agent, such as paromomycin, to eradicate the coexisting intestinal infection.

Meropenem is an effective broad-spectrum antibiotic that is often used to treat pyogenic liver abscesses. It has no role in the treatment of an amebic abscess.

Percutaneous drainage and surgical resection of an abscess are treatment options indicated for pyogenic liver abscesses. Surgical intervention is usually necessary for abscesses 5 cm or larger in size, complex abscesses, presence of gas-forming organisms, hemodynamic instability, biliary fistulization, or presence of a foreign body. These procedures are typically not needed in the treatment of amebic liver abscesses, which usually resolve with antimicrobial therapy.

Key Point

  • The mainstay of therapy for amebic liver abscesses is antibiotic therapy, such as metronidazole, plus a luminal agent, such as paromomycin, to eradicate the coexisting intestinal infection.