Amebic Liver Abscess

Adherence of E. histolytica to colonic epithelial cells is thought to be through the galactose/N-acetylgalactosamine-specific lectin. E. histolytica carries cytolytic capabilities and also kills mammalian cells through programmed apoptosis. Once E. histolytica trophozoites reach the liver, they create abscesses comprising well-circumscribed areas of cellular debris, dead hepatocytes, and liquefied cells. The lesion is surrounded by a rim of connective tissue with some inflammatory cells and amebic trophozoites. In humans, the small number of organisms compared to the actual dimensions of the abscess supports the concept that E. histolytica can destroy hepatocytes without contact with the cells.

Patients can present with amebic liver abscess months to years after travel to an endemic area, making a thorough travel history and knowledge of epidemiologic risk factors imperative. In the United States, the typical patient with an amebic liver abscess is an immigrant (usually Hispanic male) between the ages of 20 and 40. Eighty percent of patients will develop symptoms within 2 to 4 weeks of exposure, including fever, dull and aching right upper quadrant or epigastric abdominal pain, and cough. Patients who present subacutely will have weight loss and less frequent development of fever and abdominal pain. Ten percent to 35% of patients have gastrointestinal symptoms including nausea, vomiting, abdominal cramps, diarrhea, constipation, or abdominal distension. On exam, hepatomegaly with point tenderness either over the liver, below the ribs, or in the intercostal spaces is typical for liver abscess.

Patients with an amebic liver abscess will typically have evidence of leukocytosis, elevated serum transaminases, alkaline phosphatase on laboratory evaluation. On imaging, most amebic liver abscesses will be found in the right lobe. Imaging modalities include ultrasound which might show around, hypo-echoic mass, CT scan can identify a low-density mass with peripheral enhancing rim, and MRI typically shows low signal intensity on the T1-weighted image and high signal intensity on T2-weighted image, which are fairly sensitive but without absolute specificity for an amebic liver abscess. Travel history to an endemic area, coupled with typical signs and symptoms and visualization of lesions on imaging should make one consider this entity and should be followed by doing the serologic testing. Serum antigen detection has a sensitivity of over 95% with serologic testing (indirect hemagglutination) having a sensitivity of 70% to 80% in acute disease and greater than 90% in the convalescent  state. It should be noted that in the first week of the disease course, there may be false-negative serologic tests. On the other hand, stool microscopy, has a sensitivity of only 10% to 40%. [9]

Treatment entails the use of a Nitroimidazole, preferably Metronidazole at a dose of 500 mg to 750 mg by mouth 3 times per day for 7 to10 days. Alternatively, Tinidazole 2 gm by mouth daily for 3 days can be used.  Since the parasites can persist in the intestine in 40% to 60% of patients, treatment with a Nitroimidazole should always be followed with a luminal agent such as Paromomycin 500 mg 3 times a day for 7 days or Iodoquinol  650 mg three times a day for 20 days[8]. Metronidazole and Paromomycin should not be given at the same time because diarrhea, a common side effect of paromomycin, can make assessing response to therapy difficult. Around 15% of patients with amebic liver abscess fail medical treatment. Therapeutic aspiration  can be done either by percutaneous needle aspiration or by percutaneous catheter drainage. These options should be considered in patients with no clinical response to antibiotics within 5 to 7 days, in those with a high risk of abscess rupture (cavitary diameter over 5 cm or presence of lesions in the left lobe), or in cases of bacterial coinfection of amebic liver abscess.[10]. Between  percutaneous needle aspiration and percutaneous catheter drainage, studies have shown that the latter is superior with higher success rate and quicker resolution[11]

• Bacterial Liver abscess
• Echinococcus Granulosus
• Candida
• Salmonella Typhi

For simple abscess, the prognosis is excellent.

Complex abscesses and large abscesses can rupture and may be associated with a high mortality.

Overall, most patients have a favorable outcome with prompt treatment.

An amebic liver abscess may rupture into the chest, abdomen or pericardium

Rare complications include Inferior vena cava Thrombosis, Hepatic vein thrombosis, Intra abdominal mass

• General surgeon
• interventional Radiologist
• Infectious disease

Preventive measures include reducing fecal contamination of food and water and emphasizing the use of safe sexual practices, particularly in men who have sex with men. An effective vaccine would be instrumental in improving health in developing countries, particularly in children. Once considered a fatal infection, amebic liver abscess is now considered a curable condition.

Diligence in maintaining local water sources and emphasis on counseling men who have sex with men regarding safe sexual practices are of paramount importance in preventing amebiasis.

Stool studies have less than 50% positive results

Serology studies can be negative in the first week of infection

Treatment with a Nitroimidazole should always be followed with a luminal agent

The care of amebic liver abscess depends on the complexity of the liver abscess. The treatment of amebic liver abscess requires an interprofessional team to lower the morbidity and mortality of the disorder. [12]

1. The laboratory technologist is essential for the diagnosis. Serum antigen detection and stool microscopy are often the first laboratory studies ordered to make the diagnosis and rule out other pathologies.
2. For complex abscesses, Interventional radiologist will need to be consulted for image-guided drainage.
3. If the abscess is multi-locular, then the general surgeon may have to perform an open or laparoscopic surgery to help drain the collections.
4. Because many of the drugs used to treat amebic liver abscess have adverse effects, the pharmacist will need to monitor the patients. Emetin is used as a second-line drug, but it is important to monitor the patient as the drug can cause cardiac arrhythmias.
5. The nurse may need to monitor the patient in outpatient clinics to ensure that the patient is symptom-free. More importantly, the nurse plays a vital role in public education regarding sanitary measures, personal hygiene, and food washing.
6. Patients considering travel to areas where amebiasis is endemic may wish to schedule an infectious disease consult on precautions to take such as boiling drinking water, washing food regularly, and changing sexual practices to avoid fecal-oral contamination.

Outcomes

When an interprofessional team approach is undertaken, the prognosis for most patients with an amebic liver abscess is excellent.[13] To avoid complications like rupture into the lung, pericardium, or abdomen, patients with amebic liver abscess need a prompt referral to an infectious disease expert for treatment. Current evidence reveals that drainage of complex abscess can improve outcomes as opposed to medical management.[14] (Level III)