Liver Abscess: Causes, Symptoms, Treatment

A liver abscess is a pocket of pus that forms in the liver, usually due to an infection. This can happen because of an injury, an infection spreading from another part of the body, or bacteria traveling through the bloodstream. The most common types are bacterial (pyogenic) and amoebic abscesses, though some are caused by fungi or parasites. While liver abscesses are not very common, they can be serious if not treated quickly. Early diagnosis and proper treatment are important to prevent complications. This article explains what causes liver abscesses, how they are diagnosed, and the best ways to treat them, as well as the role of different healthcare professionals in managing this condition.

What is a Liver Abscess?

A liver abscess is a pocket of pus that forms in the liver due to an infection or injury. It can happen when bacteria, parasites, or fungi enter the liver through the bloodstream or from another infected area in the abdomen.

The two most common types are:

• Pyogenic liver abscess: Caused by bacteria like E. coli, Klebsiella, Streptococcus, Staphylococcus, and anaerobes.

• Amoebic liver abscess: Caused by the parasite Entamoeba histolytica, usually from contaminated food or water.

Although liver abscesses are rare, they can be very serious if not treated quickly. If left untreated, they can lead to life-threatening complications.

How Does a Liver Abscess Form?

The infection usually starts in the abdomen and spreads to the liver through the portal vein (a blood vessel that carries blood from the intestines to the liver). Common causes include:

• Leakage from the intestines due to infections or injury.

• Biliary tract infections (infections in the bile ducts) spreading directly to the liver.

Types of Liver Abscess Based on Location

Liver abscesses can also be classified by where they occur in the liver:

• Right lobe abscesses: The most common (about 50%) because this part of the liver has more blood supply.

• Left lobe abscesses: Less common.

• Caudate lobe abscesses: Rare.

Understanding liver abscesses is important because early detection and treatment can save lives.

Causes, Spread, and Development of Liver Abscess

What Causes a Liver Abscess?

In the past, appendicitis was a leading cause of liver abscess, but with better medical treatments, this now happens in less than 10% of cases. Today, the most common cause is biliary tract disease, which includes:

• Gallstones

• Narrowing of bile ducts (strictures)

• Liver or bile duct cancer

• Birth defects affecting the bile ducts

Other possible causes include:

• Cholangitis (infection of the bile ducts) – responsible for about half of bacterial liver abscesses

• Blood infections (bacteria spreading through the bloodstream)

• Intestinal infections (like diverticulitis) spreading to the liver

• Gallbladder infections

• Liver injuries from accidents or surgery

• Unknown causes (some cases have no clear origin)

The most common bacteria found in liver abscesses include:

• E. coli

• Klebsiella pneumoniae

• Streptococcus

• Staphylococcus

• Anaerobic bacteria (bacteria that grow without oxygen)

If only Streptococcus or Staphylococcus is found, doctors may check for other infections, like endocarditis (a heart infection).

In Southeast Asia, Klebsiella pneumoniae is a leading cause and is often linked to diabetes. This type of infection is usually more severe.

Parasitic Causes of Liver Abscess

1. Amoebic liver abscess – Caused by Entamoeba histolytica, a parasite that enters through contaminated food or water. It first infects the intestines and then spreads to the liver. This is rare in the U.S. but can occur in travelers or immigrants.

2. Hydatid cyst – Caused by Echinococcus granulosus, a tapeworm found in dogs. The infection develops slowly and often goes unnoticed for years.

Who Is Most at Risk? (Epidemiology)

• Liver abscess affects about 2.3 people per 100,000 each year.

• Men are more likely to develop a liver abscess than women.

• The 40-60 age group is most affected, especially when the abscess is not caused by injury.

In some regions, the rates are much higher. For example, Taiwan has an incidence of 17.6 per 100,000 people, mostly due to Klebsiella pneumoniae infections.

How Does a Liver Abscess Form? (Pathophysiology)

The liver has a rich blood supply from both the heart (systemic circulation) and intestines (portal circulation). While this helps the liver do its job, it also makes it vulnerable to infections.

The most common way bacteria reach the liver is through:

1. Leakage from the intestines → Bacteria enter the portal vein and travel to the liver.

2. Biliary system infections → Bacteria from infected bile ducts spread to the liver.

3. Bloodstream infections → Bacteria spread from another infected area in the body.

Despite this, the liver is well protected by Kupffer cells (special immune cells in the liver), which help prevent infections.

What Happens Inside the Liver? (Histopathology)

• Liver abscesses usually start as tiny pockets of pus that merge into a larger abscess.

• Infections from the bloodstream (like endocarditis or kidney infections) can also cause abscesses.

• Trauma (like an injury or surgery) can introduce bacteria directly into the liver.

Liver abscesses can also form due to:

• Cancer

• Foreign objects (such as surgical materials left inside the body)

• Complications from liver transplants

By understanding how liver abscesses develop, doctors can diagnose and treat them early to prevent serious complications.

History and Physical Examination of Liver Abscess

Gathering Patient History

Before performing tests, doctors need to take a detailed history to identify risk factors for liver abscess. Important questions include:

• Personal history – Age, gender, medical conditions

• Travel history – Some infections are more common in certain countries

• Recent infections – Past illnesses or hospitalizations

• Occupation – Some jobs expose people to parasites or bacteria

• Medications – Especially those that weaken the immune system

People at higher risk include:

• Diabetics

• People with liver disease (cirrhosis)

• Older adults

• Men (more common than in women)

• Those with weak immune systems

• People taking stomach acid-reducing medications (proton pump inhibitors)

Symptoms to Look For

Common symptoms include:

• Fever (90% of cases)

• Chills and night sweats

• Tiredness and weakness (malaise)

• Nausea and vomiting

• Right upper belly pain (sometimes spreading to the right shoulder)

• Unexplained weight loss

• Dark urine (seen in liver infections)

• Cough and shortness of breath (if the infection spreads to the lungs)

Physical Exam Findings

A doctor may notice:

• Enlarged liver (hepatomegaly)

• Yellowing of the skin and eyes (jaundice)

• Tenderness in the upper right belly

In severe cases, patients may be in shock, meaning their blood pressure drops dangerously low.

Additional symptoms in specific infections:

• Klebsiella pneumoniae infections can send infection particles to the eyes, brain, or spinal cord, causing additional complications.

• Echinococcus infections (hydatid cysts) start without symptoms but can grow for years. If a cyst bursts, it can cause severe allergic reactions (anaphylaxis).

Evaluation and Diagnosis

Lab Tests

Doctors order blood tests to check for infection and liver function:

• Complete blood count (CBC) – Checks for high white blood cell count (sign of infection)

• Liver function tests (LFTs) – Often abnormal in liver abscess cases

• C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) – Show inflammation in the body

• Blood cultures – Check for bacteria in the bloodstream

Special tests for suspected infections:

• If Entamoeba histolytica (amoebic abscess) is suspected → Stool test or blood test for the parasite

• If Echinococcus (hydatid cyst) is suspected → ELISA test for parasite antibodies

Imaging Tests (Scans)

Chest X-ray – May show signs like fluid around the lungs or an elevated diaphragm (caused by swelling in the liver).

Ultrasound (US) – First test of choice

• Can detect liver abscesses but may not always give a clear picture.

CT Scan with Contrast – Most accurate test

• Shows detailed images of the liver and abscess location.

• Can help guide a needle aspiration (removing pus to confirm infection).

Other imaging options:

• Technetium scan (80% sensitivity, less reliable than CT scan)

• Gallium scan (50-80%) and Indium scan (90%) – Less commonly used.

For hydatid cysts, an ultrasound may show the inner cyst walls separating from the main cyst

Final Diagnosis

A liver abscess is confirmed when:

1. A scan (ultrasound or CT) shows a cyst or pus-filled area in the liver.

2. A needle aspiration collects infected fluid.

3. Lab tests (cultures) confirm bacteria, parasites, or fungi in the sample.

Early diagnosis is critical to prevent serious complications, so doctors must act quickly to confirm and start treatment.