Amoebic Hepatitis Abscess

Causes of Amoebic Hepatitis Abscess

Amoebic hepatitis abscess is caused by Entamoeba histolytica, a protozoan parasite. The infection primarily occurs through the ingestion of cysts from contaminated food, water, or direct contact with fecal matter. This organism is the etiological agent of amoebiasis, which affects the gastrointestinal system. Amoebic liver abscess (ALA) is one of the most common extra-intestinal manifestations of Entamoeba histolytica infection.

Pathogenesis and Pathophysiology

The pathogenesis of amoebic hepatitis abscess begins when Entamoeba histolytica cysts are ingested and excyst in the small intestine. The trophozoites then invade the intestinal mucosa and may disseminate via the bloodstream to distant organs, including the liver. The liver is the most common site for the development of extra-intestinal amoebiasis, and the parasite typically reaches the liver through the portal venous circulation.

Upon arrival in the liver, the trophozoites induce local tissue destruction by secreting enzymes such as hyaluronidase and protease, which facilitate the degradation of extracellular matrix components, leading to necrosis. The liver’s immune response is typically unable to clear the parasite entirely, and an abscess forms as a result of the inflammatory response.

The abscess itself consists of necrotic tissue and trophozoites surrounded by a rim of inflammatory cells, including neutrophils and macrophages. Over time, the abscess enlarges, and fluid accumulation within the cavity leads to the formation of a pus-filled structure.

The formation of an abscess is usually self-contained, but complications can arise, particularly when the abscess ruptures into surrounding structures, leading to peritonitis or pleural involvement.

Epidemiology

Amoebic liver abscess is endemic in regions with poor sanitation and hygiene, particularly in parts of Asia, Africa, and Latin America. It is most commonly seen in adults aged 20-50 years, and there is a male predominance, likely due to differences in lifestyle or hygiene practices. Globally, the disease burden is significant, with approximately 50 million people affected by Entamoeba histolytica, and up to 100,000 deaths annually due to complications like liver abscess, intestinal perforation, and extra-intestinal spread.

In developed countries, amoebiasis is less common, but travelers to endemic areas or immunocompromised individuals are at increased risk. The incidence in North America and Europe is relatively low but is still reported in individuals with travel history to endemic regions, immigrants, or those with underlying health conditions that predispose them to infection.

Clinical Features

The clinical presentation of amoebic hepatitis abscess can vary from mild to severe, and it often depends on the size and location of the abscess, as well as the host’s immune response. Common clinical manifestations include:

1. Fever: One of the earliest symptoms, often associated with chills.
2. Abdominal Pain: Typically in the right upper quadrant (RUQ), which can be dull and continuous, or more severe and sharp depending on the size of the abscess.
3. Jaundice: Due to liver involvement, leading to bilirubin accumulation.
4. Weight Loss: Often seen in more chronic cases.
5. Nausea and Vomiting Resulting from the systemic infection.
6. Hepatomegaly: An enlarged liver can be palpated on physical examination.
7. Signs of Peritonitis or Pleural Effusion: If the abscess ruptures.

In some cases, the disease may be asymptomatic or present with vague symptoms such as malaise, abdominal discomfort, and low-grade fever, which can delay diagnosis. Systemic manifestations may be more pronounced in severe cases, especially if the abscess ruptures.

Imaging Findings

Imaging plays a critical role in diagnosing amoebic liver abscess and evaluating its extent. The most common imaging modalities used include ultrasound and CT scanning.

1. Ultrasound:

• The most widely available and non-invasive method. The abscess typically appears as a hypoechoic lesion with well-defined borders and possible internal echoes, reflecting the pus and necrotic tissue.
• Multiple abscesses may be present in some cases.

2. CT Scan:

• CT provides more detailed imaging and is more sensitive than ultrasound for detecting smaller abscesses.
• The abscess typically appears as a low-density, hypodense lesion in the liver parenchyma, often with a well-defined, rim-enhanced border following contrast administration.
• In some cases, the abscess may have internal septations or gas formation if the infection is complicated.

3. MRI:

• MRI is less commonly used but can be useful for distinguishing amoebic abscesses from other hepatic masses (e.g., tumors, bacterial abscesses).
• Amoebic abscesses appear as hypointense lesions on T1-weighted images and hyperintense lesions on T2-weighted images with a well-defined capsule.

Treatment

The treatment of amoebic hepatitis abscess involves both pharmacological therapy and, in some cases, surgical intervention:

1. Pharmacological Therapy:
• Metronidazole is the first-line treatment and is effective in eliminating the trophozoites. It is typically given for 7-10 days at a dose of 750 mg three times a day.
• Tinidazole is an alternative to metronidazole and is often used for its shorter duration of therapy.
• After initial treatment with metronidazole, a luminal agent such as paromomycin or iodoquinol is often prescribed to eliminate any remaining intestinal cysts and prevent reinfection.
2. Surgical Treatment:
• Surgical drainage of the abscess is required in cases where there is a large abscess, rupture, or complication such as peritonitis or pleural effusion.
• Drainage can be performed via percutaneous aspiration, laparotomy, or laparoscopy. Percutaneous drainage is the preferred method due to its lower morbidity and mortality rates compared to open surgery.
• Surgical drainage may be complicated by infection, bleeding, or injury to surrounding structures, so it is typically reserved for severe or complicated cases.
3. Adjunctive Therapies:
• Supportive treatment, including hydration, pain management, and monitoring liver function, is essential.
• Antibiotics may be necessary if there is a secondary bacterial infection or rupture leading to peritonitis.

Prognosis

The prognosis of amoebic hepatitis abscess is generally favorable with appropriate treatment. The mortality rate for patients with treated liver abscesses is low, typically less than 5%, but it increases significantly in cases with complications such as rupture, sepsis, or delayed diagnosis.

Factors that can affect prognosis include:

1. Abscess Size: Larger abscesses are more likely to cause significant complications and require more intensive treatment.
2. Complications: Rupture of the abscess into the peritoneum or pleura can lead to peritonitis or pleural effusion, significantly increasing mortality.
3. Immunocompromised States: Individuals with compromised immune systems, such as those with HIV, cancer, or diabetes, are at higher risk for severe disease and poorer outcomes.
4. Timeliness of Diagnosis and Treatment: Early detection and treatment with metronidazole lead to rapid resolution, while delays can result in more severe outcomes.

In general, the prognosis is excellent for patients who receive timely treatment. However, patients who develop complications, particularly those with large or ruptured abscesses, require prompt surgical intervention and may have a prolonged recovery.

Conclusion

Amoebic hepatitis abscess is a potentially life-threatening condition that can be successfully treated with early diagnosis and appropriate pharmacological and surgical interventions. The disease is primarily caused by Entamoeba histolytica and often occurs in individuals from regions with poor sanitation. Imaging plays a crucial role in diagnosing the condition, and treatment with metronidazole is highly effective. Although the prognosis is generally good with treatment, complications can lead to significant morbidity and mortality if not managed appropriately.

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Case Study: Amoebic Liver Abscess

Patient Information

• Name: Mr. A (Pseudonym)
• Age: 32
• Sex: Male
• Nationality: Indian
• Presenting Complaint: Right upper quadrant abdominal pain, fever, jaundice
• Medical History: No significant past medical history. No known comorbidities.

Clinical Presentation

Mr. A, a 32-year-old male, presented to the emergency department with a 5-day history of fever, right upper quadrant abdominal pain, and jaundice. The patient reported the pain as dull and constant, exacerbated by deep breathing and palpation. He had also experienced a 5-kg weight loss over the past month. He mentioned recent travel to rural areas in India, where he had consumed potentially contaminated water and food. His fever was high-grade, and he had chills along with the abdominal pain.

On examination, he had yellow sclerae (suggestive of jaundice), tachycardia, and right upper quadrant tenderness without rebound tenderness. He was febrile with a temperature of 39.5°C. The liver was palpable 2 cm below the right costal margin, and the spleen was not enlarged.

Initial Investigations

• Complete Blood Count (CBC): Elevated white blood cell count (12,500/µL) with a predominance of neutrophils. Hemoglobin was normal.
• Liver Function Tests: Elevated liver enzymes (ALT 250 U/L, AST 320 U/L), elevated bilirubin (total bilirubin 4.5 mg/dL, direct bilirubin 3.1 mg/dL).
• C-Reactive Protein (CRP): Elevated (45 mg/L).
• Ultrasound of the Abdomen: Revealed a large hypoechoic lesion in the right lobe of the liver, measuring 6 cm in diameter. No internal echoes were noted, and the margins were well-defined, suggesting an abscess.

Serological Tests for Hepatitis: Negative for hepatitis A, B, and C.

Quiz:

1.   What is the primary causative organism of amoebic liver abscess?

(1)   Toxoplasma gondii

(2)   Entamoeba histolytica

(3)   Plasmodium falciparum

(4)   Giardia lamblia

2.   Which of the following is NOT a typical symptom of amoebic liver abscess?

(1)    Right upper quadrant abdominal pain

(2)    Fever

(3)    Vomiting

(4)    Jaundice

3.   Which drug is primarily used in the treatment of amoebic liver abscess?

(1)    Amoxicillin

(2)    Metronidazole

(3)    Azithromycin

(4)    Ceftriaxone

4.   What is the most important imaging method for diagnosing an amoebic liver abscess?

(1)    MRI

(2)    Ultrasound

(3)    X-ray

(4)    CT scan

5.   Where is amoebic liver abscess most commonly found?

(1)    North America

(2)    Europe

(3)    Africa

(4)    Developing countries

6.   What treatment is required if the abscess is large or complicated?

(1)    Percutaneous drainage

(2)    Additional antibiotics

(3)    High-protein diet

(4)    Surgical removal

7.   What is the primary route of transmission for amoebic liver abscess?

(1)    Bloodborne transmission

(2)    Fecal-oral route

(3)    Airborne transmission

(4)    Contact transmission

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Diagnosis

The clinical features of fever, abdominal pain, jaundice, hepatomegaly, and imaging findings (hypoechoic lesion on ultrasound) strongly suggested an amoebic liver abscess. Given Mr. A’s travel history to an endemic area and the absence of other potential causes of the liver lesion, a presumptive diagnosis of amoebic liver abscess was made.

Treatment

Mr. A was started on metronidazole 750 mg orally three times a day for 10 days. A luminal agent, paromomycin 500 mg three times daily, was also prescribed to treat any residual intestinal infection. The patient was admitted to the hospital for supportive management, including hydration and monitoring of liver function.

After 48 hours of treatment, the fever subsided, and Mr. A reported a significant decrease in pain. His liver function tests showed a marked reduction in enzyme levels (ALT 95 U/L, AST 125 U/L), and his bilirubin began to normalize.

Given the favorable response to medical management, percutaneous drainage was not needed, and Mr. A was discharged after completing a 10-day course of metronidazole and a 7-day course of paromomycin.

Follow-Up

Mr. A was seen in the outpatient clinic 2 weeks after discharge. He was asymptomatic with no complaints of abdominal pain or jaundice. On physical examination, the liver was no longer palpable, and laboratory tests showed normalization of liver function tests.

A follow-up ultrasound was performed at 6 weeks, which revealed complete resolution of the abscess with no residual lesion.

Discussion

This case highlights the typical presentation and management of amoebic liver abscess, a disease most commonly seen in endemic regions with poor sanitation. The patient’s symptoms, imaging findings, and travel history led to the diagnosis of Entamoeba histolytica infection.

Amoebic liver abscess is a result of hematogenous spread of E. histolytica from the colon to the liver, where the trophozoites cause tissue necrosis and abscess formation. The diagnosis is usually made based on clinical presentation, imaging findings, and travel history. While the majority of cases are managed with metronidazole and luminal agents, surgical drainage is required only in severe cases or when complications such as rupture occur.

This case was successfully managed with medical treatment alone, and the patient experienced complete resolution. Early diagnosis and treatment are crucial for a good prognosis, with a low mortality rate if treated promptly.

Conclusion

Amoebic liver abscess should be considered in patients presenting with fever, right upper quadrant pain, and jaundice, particularly those with a history of travel to endemic areas. Early initiation of appropriate therapy, including metronidazole, is typically effective. Surgical intervention is rare, but percutaneous drainage may be required in cases of large or complicated abscesses. The prognosis is excellent with timely treatment.

Reference

(1)  Stanley SL Jr. Amoebiasis. The Lancet. 2003;361(9362):1025–1034. doi:10.1016/S0140-6736(03)12830-9

(2)    Shirley DA, Farr L, Watanabe K, Moonah S. Amebiasis: From Morbidity to Mortality. Clinical Microbiology Reviews. 2018;31(4):e00025-17. doi:10.1128/CMR.00025-17

(3)    Petri WA Jr, Haque R, Lyerly D, Vines RR. Estimating the impact of amebiasis on health. Parasitology Today. 2000;16(8):320–321. doi:10.1016/S0169-4758(00)01679-8

(4)    Blessmann J, Tannich E. Treatment of asymptomatic intestinal Entamoeba histolytica infection. Trends in Parasitology. 2002;18(7):316–317. doi:10.1016/S1471-4922(02)02302-2

(5)    Makkar RP, Sachdev GK, Malhotra V. Comparison of aspiration and non-aspiration in the management of amebic liver abscess: a clinical and sonographic study. American Journal of Gastroenterology. 2001;96(2):397–403. doi:10.1111/j.1572-0241.2001.03540.x