Amoebic Liver Abscess : Epidemiology, Pathogenesis

Epidemiology of Amoebic Liver Abscess

• It is common in tropical and developing countries.
• It is mostly seen in the age group of 20-40 years.
• Heavy consumption of alcohol increases the risk of Amebic liver abscess.
• It is more commonly seen in Hispanic males, and there is a low incidence in menstruating females.
• There will be a history of travel to endemic areas.
• There is an increased risk of Amoebic Liver Abscess in poverty as the population is living in cramped living conditions.  
• If patients have impaired host immunity, there is an increased risk of infection and a higher mortality rate. 
• Even if there is no history of travel to endemic areas, there is still an increased risk of amoebic Liver abscess.
  • If the patient is HIV positive
  • If the patient is malnutrition
  • If the patient is suffering from chronic infection
  • If the patient is using chronic steroids

Pathogenesis Of  Amoebic Liver Abscess 

The usual pathophysiology for pyogenic liver abscesses is bowel content leakage and peritonitis. Bacteria travel to the liver via the portal vein and reside there. Infection can also originate in the biliary system. Hematogenous spread is also a potential etiology.

Amoebic liver abscesses are well-circumscribed regions that contain necrotic material (dead hepatocytes, liquefied cells, and cellular debris) and the surrounding fibrinous border. The adjacent liver parenchyma is usually normal. The abscesses can be single or multiple.

Route Of  Amoebic Liver Abscess 

The route of infection is feco-oral, which means that the disease is contracted through the use of contaminated food and water. Humans are the principal host, and the source of infection is human contact with cyst-passing carriers. The patients are asymptomatic in this condition. These patients pass quadrinucleate cysts in the fecal matter. Quadrinucleate cyst is the infective stage, where the cyst undergoes further division, which will convert into an octanucleate cyst. It is going to release around 8 trophozoites, which are released into the small intestine. These trophozoites are passed into the colon. When the trophozoites pass into the colon, it leads to the formation of a flask-shaped ulcer. Inflammation in the colon is called amoebic colitis, and an inflammatory mass is known as ameboma. The most common site is caecum and ascending colon. Trophozoites cause flask-shaped ulcers and penetrate capillaries, and via capillaries, they enter into superior mesenteric veins, portal veins, and the liver.

Entamoeba histolytica causes histolysis and necrosis of hepatocytes and WBCs. There will be necrosed material in the center, and trophozoites will be present in the periphery. There is enzymatic cellular hydrolysis. There is necrosis of hepatocytes. The cavity contains proteinaceous acellular debris. There is a formation of antiamoebic antibodies. 

Clinical Features Of  Amoebic Liver abscess

• Abdominal pain is the most common symptom. The typical duration of the symptoms is < 10 days.
• Right upper quadrant pain and tenderness can also be experienced by the patient.
• There is a fever with chills, but it is less commonly seen.
• The patient will have anorexia and hepatomegaly. 
• Diarrhea is seen in only one-third of people with amoebic liver abscess)
• Irritation of diaphragm 
• Ruptures of the abscess cavity into the peritoneum lead to peritonitis, which is more common in the left lobe as it is not supported.
• Jaundice is rare.
• There is a synchronous hepatic abscess in patients with active colitis, and is seen in ⅓ of the patients. 

Acute Presentation Of  Amoebic Liver abscess

Acute presentation symptoms are present for < 10 days of the condition. Patients have a more dramatic presentation. The patient has a Fever with chills, abdominal tenderness, and multiple lesions. The most common LFT abnormalities are raised PT and INR. 

Chronic Presentation Of  Amoebic Liver abscess

In chronic presentation, symptoms are present for > 2 weeks. The cavity is single, and it is right-sided in more than 80% of the patients. 

Diagnosis Of  Amoebic Liver abscess

• For diagnosis, ultrasound  and CT are highly recommended. 
• Diagnosis is confirmed by serology. Antibodies are detected by ELISA. 
• Chest X-rays are abnormal in 50% of patients.
  • Findings – Elevated right hemidiaphragm, reactive right-sided pleural effusion, atelectasis. 
  • Here, the abscess cavity is rounded. 
  • Glycans capsule is resistant to hydrolysis by amoeba. 

Treatment Of  Amoebic Liver abscess

• If there is no frank pus, then there is no need for drainage. 
• Antibiotics – High dose oral metronidazole i.e., 750 mg TDS for 10 days. In more than 90% of the patients, it is curative and will show clinical improvement in just three days typically. 
• Luminal agents are given to treat the carrier stage:
  • Paromomycin
  • Iodoquinol
  • Diloxanide furoate 
• 3-9 months are required for the radiological resolution.
• Indications of the aspirations of the amoebic liver Abscess
  • Diagnostic uncertainty.
  • There is a failure to respond to the medical treatment within 3-5 days.
  • Bacterial superinfection.
  • There is a high risk of rupture.
    • Whenever the size of the abscess cavity is> 5 cm, the left lobe abscess is at a high risk of rupture. 
• Pregnancy is another indication of amoebic Liver absence. 
• Indications of laparotomy in Amoebic Liver abscess :
  • In the presence of hollow viscus perforation.
  • If there is a doubtful diagnosis. 
  • In the condition where there is failure of conservative therapy.
  • If fistulisation results in haemorrhage or sepsis. 

Complications In Amoebic Liver abscess

• The most common complication is rupture, mostly in the peritoneal cavity > pleural cavity > Pericardial cavity.
• The most common risk factor associated with the rupture includes size, i.e., > 5cm. 
• The incidence of the rupture is around 3-17%.
• For rupture – Exploratory laparotomy, peritoneal lavage, and insertion of drainage is done. 

• The treatment for the rupture into the pleural space - thoracentesis. 
• Rupture into the bronchi is self-limited by postural drainage and bronchodilators.  
• Rupture into the pericardium is considered an emergency.
  • Perform needle pericardiocentesis and further go for drainage by pericardiotomy. 

Prognosis of Amoebic Liver abscess

• The mortality rate is around 5%.
• Factors associated with the poor outcomes include the following:
  • Increased serum bilirubin - >3.5mg/dL. 
  • Encephalopathy.
  • Hypoalbuminemia (<2gm/dL) and multiple abscess cavities lead to poor outcomes.
  • Abscess volume (>500ml)
  • Anemia and diabetes 
• Clinical improvement occurs within 3 days, and the average time required for radiological resolution is 3-9 months. 

Also Read: Tubes, Catheters And Drains

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