What is an Amebic Liver Abscess?

An amebic liver abscess is a pus-filled cyst that develops inside the liver following a severe parasitic infection. Abscesses develop when Entamoeba histolytica (E. histolytica), the parasite that causes dysentery, penetrates the walls of the digestive tract and migrates to the liver from the bloodstream. Infection can cause a number of uncomfortable symptoms, including high fever, chills, fatigue, and upper abdominal pain. Treatment is usually targeted at killing parasites with medications instead of repairing or removing the actual abscess, though surgical drainage of the cyst may be necessary if severe liver inflammation occurs.

E. histolytica is found worldwide and is transmitted from host to host through contact with infected feces. In most cases, infection is due to ingesting contaminated food or water. A person of any age can develop an amebic liver abscess, though middle-aged adults who live in or travel to poor, crowded regions are at the highest risk of infection. Males tend to experience liver complications more often than women, though doctors are unsure why.

Once E. histolytica parasites are ingested, they pass through the stomach and attach to the walls of the small intestine. Parasites gradually break down the walls and escape into the bloodstream. As blood naturally passes through the liver, the parasites cling to the lining of the liver and take advantage of available proteins to mature, reproduce, and colonize. An amebic liver abscess can develop in as little as one week after the initial infection.

Worsening abdominal pain and fever are the most common symptoms of an amebic liver abscess. Many patients experience gastrointestinal problems as well, such as diarrhea, vomiting, joint pain, and fatigue. An untreated infection may spread from the liver to other vital organs, especially the lungs and heart. If infection becomes widespread, breathing difficulties, vision changes, elevated heart rate, and mental confusion can become debilitating.

A doctor can usually diagnose an amebic liver abscess by analyzing blood samples and taking imaging scans of the abdomen. Blood cultures that return positive for E. histolytica are clear signs that infection is present. Ultrasounds and computerized tomography scans can reveal round, well-defined lesions on or near the surface of the liver. After confirming a diagnosis and gauging the size of the abscess, specialists can determine the best course of treatment.

Most cases of E. histolytica infection in either the digestive tract or the liver can be cured with a ten-day course of medications called amebicides. Metronidazole is the most commonly prescribed amebicide for amebic liver abscesses. Patients usually see improvements in symptoms within a few days and fully recover in less than one month. Occasionally, a doctor will decide to drain fluid from an abscess manually with a needle to provide more immediate symptom relief. Follow-up visits are important to ensure infection does not return.