Amebic Liver Abscess Overview

Study Notes

Amebic Liver Abscess

Caused by Entamoeba histolytica, a protozoan that infects the colon and can spread to the liver.
Commonly seen in travelers to South Asia, Central, and South America.
Abscess formation occurs when the parasite invades the colonic mucosa, enters the portal circulation, and lodges in the liver.
Abscess characterized by necrotic tissue and the trophozoite form of Entamoeba.

Clinical Features

Right upper quadrant pain, often dull and aching.
Fever, night sweats, and malaise.
Hepatomegaly and tenderness on palpation.
Cough or pleuritic chest pain in cases of large abscesses causing diaphragmatic irritation.
Jaundice is rare but can occur in large abscesses compressing the bile ducts.

Diagnosis

Serology: Antibodies against E. histolytica are usually positive.
Imaging:
- Ultrasound: Shows a hypoechoic lesion in the liver.
- CT scan: Shows a well-defined, low-attenuation area often in the right lobe.
Stool examination: Rarely helpful, as cysts are not often present in the stool during liver abscess formation.

Treatment

Antiparasitic therapy:
- Metronidazole: Drug of choice for amebic liver abscess, typically given for 10 days.
- Paromomycin: Given afterward to eradicate luminal cysts and prevent recurrence.
Drainage:
- Generally not required unless:
  - The abscess is large (>10 cm).
  - Risk of rupture into the peritoneal or pleural space.
  - The patient does not improve with medical treatment alone.
- Percutaneous or catheter drainage can be performed.

Complications

Rupture: Into the pleural, peritoneal, or pericardial spaces.
Secondary bacterial infection: Superinfection with pyogenic organisms.
Chronic abscess: Failure to resolve after therapy may suggest a different diagnosis, such as a pyogenic abscess or malignancy.

Congenital Liver Cysts

Benign fluid-filled cavities in the liver present at birth.
Often incidental findings and usually asymptomatic unless they enlarge significantly.

Etiology

Thought to arise from congenital malformation of the bile ducts.
Includes:
- Simple liver cysts: Most common, filled with clear fluid.
- Polycystic liver disease: Associated with autosomal dominant polycystic kidney disease (ADPKD).
- Choledochal cysts: Congenital dilations of the biliary tree.

Clinical Features

Asymptomatic: Most congenital liver cysts are detected incidentally on imaging for unrelated reasons.
Symptomatic cases:
- Abdominal discomfort or fullness.
- Early satiety due to compression of nearby organs by large cysts.
- Jaundice or cholangitis (in the case of choledochal cysts).

Diagnosis

Ultrasound: The first-line imaging modality, showing anechoic, well-circumscribed lesions.
CT scan or MRI: Provides more detailed images of cyst size, location, and any communication with the bile ducts.
Liver function tests: Usually normal unless the cysts cause biliary obstruction.

Treatment

Observation: Most simple liver cysts do not require treatment unless they become symptomatic or show signs of complications.
Percutaneous drainage: Used for symptomatic relief in large cysts but carries a risk of recurrence.
Surgical excision:
- Indicated in cases of symptomatic or rapidly enlarging cysts.
- Laparoscopic fenestration (unroofing of the cyst) is commonly performed.
Management of polycystic liver disease:
- Treatment focuses on symptom relief.
- Surgical options include fenestration or liver transplantation in severe cases.

Complications

Cyst infection: Rare but can occur, requiring antibiotics and possibly drainage.
Biliary obstruction: If the cyst compresses the bile ducts.
Malignant transformation: Extremely rare but possible, especially in complex or multiloculated cysts.

Description

This quiz explores the causes, clinical features, and diagnostic methods related to amebic liver abscess caused by Entamoeba histolytica. It covers signs, symptoms, and imaging techniques necessary for effective diagnosis. Suitable for medical students and healthcare professionals.