Introduction:
Amoebic liver abscess is a type of liver abscess which occurs in response to an intestinal parasite called Entamoeba histolytica. The parasite causes amebiasis which is seen worldwide and is more common in tropical countries with crowded people and poor sanitation areas. It is also known as hepatic amebiasis or extraintestinal amebiasis. Men between the age of 18 and 50 are mostly affected.
What Is the Cause of Amoebic Liver Abscess?
Amoebic liver abscess is caused by Entamoeba histolytica, the same organism that causes the intestinal disease amebiasis. After the infection, the parasite is carried through the bloodstream from the intestine to the liver. Amebiasis spreads from eating food or water contaminated with feces. They also spread from person to person.
What Is the Pathophysiology of the Disease?
Entamoeba histolytica exists in two forms: the cyst form, which is the inactive form, and the trophozoite form, which causes the disease. Infected people shed cysts in their feces which are transmitted to others by contaminated food and water. Rarely the transmission occurs through oral or anal sex. When cysts reach the digestive tract, they break down and release trophozoites which adhere to the lining of the digestive tract and cause the disease.
Liver involvement occurs when the Entamoeba histolytica enters the portal circulation into mesenteric veins and travels to the liver, where they form one or more abscesses. The right lobe of the liver is more commonly affected than the left lobe. This is due to the fact that the right lobe is supplied predominantly by a superior mesenteric vein, and the left lobe is supplied by a splenic vein.
What Are the Risk Factors for Amoebic Liver Abscesses?
Factors that increase the risk of an amoebic liver abscess include:
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Recent travel to tropical countries.
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Malnutrition.
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Old age.
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Pregnancy.
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Immunosuppression including, human immunodeficiency virus infection and acquired immunodeficiency syndrome.
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Steroid use.
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Alcoholism.
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Men who have sex with men.
What Are the Symptoms of an Amoebic Liver Abscess?
Approximately 90 % of people with Entamoeba histolytica infection are asymptomatic. A liver abscess can develop within two to four weeks after the first infection and develops in less than 4 % of patients. People with amoebic liver abscess shows some symptoms including:
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Abdominal pain particularly in the right upper region. Pain is intense, continuous, or stabbing. The pain increases on coughing, walking, and deep breathing and when the patient rests on the right side.
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Fever.
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Chills.
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Sweating.
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Loss of appetite.
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Non-bloody diarrhea.
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Weight loss.
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Jaundice (yellowing of the skin and eyes).
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Joint pain.
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General discomfort and uneasiness.
How Can We Diagnose Amoebic Liver Abscesses?
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The doctor asks about the symptoms and travel history to tropical countries.
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Examination of the abdomen to rule out the tenderness in the stomach (typically in the right upper part of the abdomen). Hepatomegaly with pain on palpation is one of the most important signs of amoebic liver abscess. Tenderness over the liver, below the ribs, or in the intercostal space is a typical finding.
The following tests are used in the diagnosis of amoebic liver abscess, including:
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Complete blood count shows elevated serum transaminase. Alkaline phosphatase is elevated in 70 % of the cases with amoebic liver abscess. The blood test also reveals elevated white blood cell (WBC) count - leukocytosis and elevated bilirubin levels. Eosinophilia is rare, and anemia may also be present.
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Serologic testing is the most widely used method for diagnosing amoebic liver abscesses. This test detects antibodies specific for Entamoeba histolytica in most of the patients with extraintestinal amebiasis.
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A stool test is also done for the diagnosis. Three or more stool samples are tested for the presence of trophozoites of Entamoeba histolytica.
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Abdominal ultrasound is done to rule out liver enlargement.
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Abdominal computed tomography scan shows the abscess in low density with smooth margins and contrasts peripheral rim is seen.
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Aspiration of the liver abscess and liver biopsy is rarely done for diagnosis.
What Is the Treatment for Amoebic Liver Abscess?
Antibiotics such as Metronidazole or Tinidazole are given. Metronidazole is given at a dose of 500 mg to 750 mg 3 times per day for seven to ten days. Side effects of Metronidazole include nausea, a metallic taste in the mouth, and headache. Alternatively, Tinidazole is given at a dose of 2 gm by mouth daily for three days.
The treatment should be followed by luminal agents. Paromomycin is given at a dose of 500 mg three times a day for seven days or Iodoquinol 650 mg three times a day for 20 days. Metronidazole and Paromomycin should not be given together because of the side effect. Around 15 % of the patients fail the medical treatment for amoebic liver abscess.
In some cases, the abscess needs to be drained using a catheter or surgery to relieve symptoms and increase the success of the treatment. This is done in patients with no response to medical treatment. Without treatment, the abscess may rupture and spread to other organs leading to death.
What Are the Complications?
The abscess may rupture and spread to the abdominal cavity or lungs, presenting as a pleural effusion, heart as a pericardial effusion, and sometimes to the brain.
What Are the Preventive Measures?
No prophylactic vaccine is currently available for amebiasis. When traveling in poor sanitation countries, drink purified or boiled water. Washing hands after eating and using the toilet can prevent infection. Avoid eating uncooked food and unpeeled fruit.
The following items are not considered safe and to be avoided:
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Drinks with ice cubes.
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Unpeeled fruit or vegetables.
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Milk, cheese, or dairy products that are not pasteurized.
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Food or beverages are sold by street vendors.
Conclusion:
Amoebic liver abscess is the most common extraintestinal manifestation of amebiasis. In most cases, rapid improvement in the symptoms is seen within one week after treatment with antiemetic medications.
