What is Amebic Liver Abscess?
Amebiasis is a sickness caused by a tiny organism (protozoan) called Entamoeba histolytica. It’s usually spread when someone ingests tiny particles of poop. This infection may not show any signs in some people, but it can also lead to complications like liver abscesses (pus-filled pockets in the liver). The most common serious effect outside the intestines or gut is this type of liver issue. Generally, the people most likely to get this parasite are men between 18 and 50 years old. Countries like India, Africa, Mexico, and Central and South America typically see more cases of this infection. Roughly 80% of people with amebiasis will start to see symptoms within 2 to 4 weeks, like a fever, and pain in the upper right part of their tummy. About 10% to 35% of patients also have associated digestive issues. The disease is identified based on the symptoms, the patient’s history and environment, together with imaging studies and blood tests. The preferred therapy includes a medication called Metronidazole followed by another one known as Paromomycin which works in the gut. In rare cases, a procedure where the pus is sucked out from the liver may be required. The first case of a liver abscess in the USA was diagnosed by Sir William Osler.
What Causes Amebic Liver Abscess?
Entamoeba histolytica is a type of parasite that can cause a condition known as amoebic colitis. Amoebic colitis is a type of stomach infection that can cause serious symptoms. It is estimated that Entamoeba histolytica is responsible for around 40 million infections every year and results in up to 100,000 deaths.
Interestingly, there is another similar parasite named E. despar that can also infect humans. However, this parasite usually doesn’t cause any illness and people who have it may not show symptoms or feel sick. This is referred to as being an asymptomatic carrier.
There are many different types of Entamoeba, including E. dispar and E. moshkovskii, that can infect humans, but only E. histolytica causes amebiasis, which is a particular kind of infection. Both humans and non-human primates, such as monkeys and apes, can host E. histolytica, which explains how the infection spreads.
Risk Factors and Frequency for Amebic Liver Abscess
Amebic liver abscess, a rare condition that mainly affects the liver, is ten times more common in men than in women. This is particularly seen among individuals aged between 18 and 50. It’s unclear why there’s such a difference, but factors might include hormonal effects and alcohol consumption.
In the United States, most amebic liver abscess cases are seen in immigrants from areas where the condition is common or in people who live near the Mexico border. Worldwide, high infection rates are observed in India, Africa, Mexico and parts of Central and South America.
The condition is mostly caused by consuming contaminated food or water, but it can also be transmitted through oral and anal sex, particularly among men who have sex with men. It’s important to note that out of those who have intestinal amebiasis, about 2% to 5% may develop a liver abscess.
This condition is prevalent worldwide and poses a significant risk in countries where there’s inadequate sanitation of municipal water supplies.
Signs and Symptoms of Amebic Liver Abscess
An amebic liver abscess is a condition that can occur months or even years after a person has traveled to an area where the disease is common. It’s crucial to know about someone’s travel history and understand the risks associated with this condition. Usually, the people at highest risk in the United States are immigrants, specifically Hispanic males between the ages of 20 and 40.
Around 80% of those affected will start showing symptoms within 2 to 4 weeks of being exposed. These symptoms can include fever, a dull pain in the upper right side of the stomach or below the sternum, and a cough. Some patients don’t show these symptoms right away and instead lose weight and less commonly show fever and abdominal pain symptoms. Additionally, between 10% to 35% of people may experience symptoms related to the stomach and intestines, such as nausea, vomiting, stomach cramps, diarrhea, constipation, or bloated stomach.
When examined by a doctor, those with a liver abscess typically show signs of an enlarged liver with tenderness either directly over the liver, under the ribs, or in the spaces between the ribs.
Testing for Amebic Liver Abscess
If your doctor suspects you have an amebic liver abscess, they will conduct several tests. These include blood tests to check for a high white blood cell count and elevated liver enzymes, also known as ‘serum transaminases’ and ‘alkaline phosphatase’. High levels of these enzymes usually suggest a problem with the liver.
Imaging tests like ultrasound, CT scan, and MRI can also provide further information. These tests show pictures of your liver and can help the doctor find any abscesses, or pockets of infection. Most of the time, the abscess is found in the right part of the liver. An ultrasound might show a round, low-echo mass, whereas a CT scan can reveal a low-density mass with a glowing rim around it. An MRI typically shows a mass that is dark on T1-weighted image and bright on T2-weighted image. Although these tests can detect an amebic liver abscess, they can’t always confirm it with 100% certainty.
If you’ve recently traveled to a region where the amoeba that causes the liver abscess is common and you have the typical signs and symptoms of the disease, your doctor will likely order further tests. These include serologic tests and antigen detection tests that look for the presence of the amoeba in your blood. These tests are very accurate, with antigen detection having a success rate of over 95%, and serologic tests having a 70-80% success rate in early disease and over 90% in later stages of illness. However, these tests may not always be accurate during the first week of the disease.
In contrast, stool microscopy, a test that looks for the amoeba in your stool, only has a 10-40% success rate. This means it often fails to detect the amoeba, so negative results don’t necessarily rule out an amebic liver abscess.
Treatment Options for Amebic Liver Abscess
Treatment for this condition usually involves the use of a type of drug called a Nitroimidazole, with Metronidazole being the preferred choice. This helps to kill the parasites causing the illness. Even after taking this medication, it’s important to note that the parasites can still persist in the intestine in about 40% to 60% of patients. Because of this, your treatment will often include an additional medication such as Paromomycin or Iodoquinol to help clear the remaining parasites from the intestine.
It’s also important to remember that Metronidazole and Paromomycin should not be taken together, as it can be hard to gauge the effectiveness of the treatment due to the common side effect of diarrhea that Paromomycin may cause.
Even with this combination of drugs, around 15% of patients who have a condition called an amebic liver abscess – a collection of pus in the liver due to a parasitic infection – don’t respond to medication alone. If you fall into this category, there are other treatments that can be considered. For example, therapeutic aspiration, a procedure where the fluid is removed from the abscess, can be a good option. This procedure can be done in two ways: by inserting a needle into the abscess (percutaneous needle aspiration) or by inserting a tube to drain the abscess (percutaneous catheter drainage). Research shows that the latter option tends to work better with a higher success rate and quicker resolution time.
This procedure is generally considered in patients who don’t respond to antibiotics within a week, in those with a high risk of the abscess bursting (for example, if the abscess is more than 5 cm in diameter or lesions are present in the left lobe of the liver), or in cases where a bacterial infection is also present along with liver abscess.
What else can Amebic Liver Abscess be?
- Bacterial liver abscess
- Echinococcus Granulosus (a type of tapeworm infection)
- Candida (a type of yeast infection)
- Salmonella Typhi (the bacteria that causes typhoid fever)
What to expect with Amebic Liver Abscess
The outlook is generally very good for simple abscesses.
However, complex or large abscesses can burst, and this can sometimes be connected with a high risk of death.
But overall, most patients see positive results if they receive treatment quickly.
Possible Complications When Diagnosed with Amebic Liver Abscess
A liver abscess caused by amoebae (single-celled organisms) can potentially rupture, spreading infection into the chest, abdomen, or the sac around the heart.
There are also a few rare complications to look out for:
- A clot in the inferior vena cava, a major vein that carries blood from lower body to the heart
- A clot in the hepatic vein, which drains blood from the liver
- A mass forming inside the abdomen
Preventing Amebic Liver Abscess
Prevention methods against this condition involve lessening the chances of food and water coming in contact with human waste, and reminding people—especially men who are sexually active with other men—about the significance of safe sexual behaviors. An effective vaccine could make a huge difference in improving the health of people in developing countries, particularly children. Whereas in the past, an abscess in the liver caused by amoebas—a type of parasite—was thought to be life-threatening, it is now regarded as a condition that can be treated successfully.
