A liver abscess is a localized collection of pus that forms when the body’s immune system walls off an infection within the liver tissue. The pus is a thick fluid made of dead white blood cells, germs, and damaged tissue cells, all enclosed by a fibrous capsule.
Formation and Underlying Causes
A liver abscess develops when infectious microorganisms are introduced into the liver tissue through several pathways. One of the most common routes is via the biliary tract, the system of ducts that carries bile from the liver and gallbladder. An infection in the gallbladder or bile ducts, such as cholangitis, can ascend directly into the liver, providing a path for bacteria to establish an abscess.
Another pathway is through the portal vein, which carries blood from the gastrointestinal tract to the liver. Infections elsewhere in the abdomen, such as appendicitis or diverticulitis, can release bacteria into this vein. These bacteria are then filtered out by the liver, where they can multiply and form an abscess. Less commonly, infections can spread through the hepatic artery, which supplies oxygenated blood to the liver, carrying bacteria from a bloodstream infection (sepsis).
The specific microorganism causing the infection determines the type of abscess. The vast majority are pyogenic abscesses, caused by bacteria like Escherichia coli and Klebsiella pneumoniae. Amebic liver abscesses are caused by the parasite Entamoeba histolytica, which results from an intestinal infection known as amebiasis. Fungal abscesses can also occur, particularly in individuals with compromised immune systems.
Identifying Symptoms
The signs of a liver abscess develop gradually and can be mistaken for other illnesses. The most frequently reported symptoms are a persistent fever, accompanied by chills and profuse sweating. Patients also experience a distinct pain localized to the upper right quadrant of the abdomen, which may feel like a dull, throbbing ache. This discomfort occurs because the growing abscess stretches the capsule surrounding the liver, which is rich in nerve endings.
Alongside these primary indicators, a person may experience a general feeling of being unwell, known as malaise. This can be coupled with a loss of appetite, leading to unintentional weight loss over weeks. Nausea and vomiting are also common, further contributing to poor nutrition and fatigue.
In some cases, as the abscess interferes with the liver’s ability to process bilirubin, the skin and whites of the eyes may take on a yellowish tint, a condition called jaundice. The abdomen might feel tender to the touch, particularly over the liver area, and some individuals may notice their liver feels enlarged. Occasionally, the inflammation can irritate the diaphragm, leading to a cough or pain in the right shoulder.
Diagnostic Procedures
Confirming a liver abscess involves a combination of laboratory tests and medical imaging. Blood tests, such as a complete blood count (CBC), can reveal a high white blood cell count, indicating an infection. Liver function tests may also show abnormal enzyme levels, suggesting liver damage or inflammation.
Imaging studies are used to visualize the abscess. An abdominal ultrasound is often the first imaging technique used because it is non-invasive and widely available. For a more detailed view, a computed tomography (CT) scan provides cross-sectional images that can precisely locate the abscess, determine its size, and identify if there are multiple abscesses. Magnetic resonance imaging (MRI) can also be used to characterize the lesion.
To finalize the diagnosis and guide treatment, a procedure to sample the abscess fluid may be performed. Using either ultrasound or CT as a guide, a physician inserts a thin needle through the skin and into the abscess to withdraw a sample of the pus. This fluid is then sent to a laboratory for culture, which allows for the identification of the specific bacteria, fungus, or parasite causing the infection.
Treatment and Management
The standard approach to treating a liver abscess is twofold, combining medication to control the infection with a procedure to drain the pus. Once an abscess is diagnosed, treatment begins immediately with broad-spectrum antibiotics administered intravenously to ensure high concentrations in the bloodstream. The choice of antibiotic may be adjusted once laboratory results identify the specific microorganism. This antibiotic course can be lengthy, lasting for several weeks.
In addition to antimicrobial therapy, drainage of the abscess is necessary to remove the source of infection and relieve pressure. The most common method is percutaneous drainage, a minimally invasive procedure performed by an interventional radiologist. Guided by ultrasound or CT imaging, the radiologist inserts a needle and then a thin tube, called a catheter, through the skin and into the abscess cavity to drain the pus. This catheter may be left in place for several days for continuous drainage.
For abscesses that are very large, difficult to reach, or do not respond to percutaneous drainage, a surgical procedure may be required. Surgery allows for the abscess to be opened and washed out completely. With prompt diagnosis and appropriate treatment, the outlook for patients with a liver abscess is generally positive. Follow-up imaging scans are performed after treatment to confirm that the abscess has fully resolved.