Amoebic liver abscess overview
Synonyms and keywords: Hepatic amoebiasis; Extraintestinal amoebiasis; Abscess-amoebic liver

# Overview
Amoebic liver abscess is caused by a protozoan Entamoeba histolytica. Is it an inflammatory space occupying lesion in liver.

# Historical Perspective
Amoebiasis was first described as a deadly disease by Hippocrates. . The first case of amoebiasis was documented in 1875.

# Classification
Liver abscess may be classified into 3 types based on etiology into pyogenic, amoebic, and fungal liver abscess.. Based on duration of symptoms, amoebic liver abscess is classified into acute and chronic.

# Pathophysiology
Ameobic liver abscess is caused by a protozoan Entamoeba histolytica. It is the most common extraintestinal manifestation of amoebiasis. The mode of transmission of Entamoeba histolytica include fecal-oral route (ingestion of food and water contaminated with feces containing cysts), sexual transmission via oral-rectal route in homosexuals, vector transmission via flies, cockroaches, and rodents. Hepatocyte programmed cell death induced by Entamoeba histolytica causes amoebic liver abscess. The infection is transmitted to liver by portal venous system.

# Causes
Amoebic liver abscess is caused by a protozoan Entamoeba histolytica.

# Differential Diagnosis
Amoebic liver abscess must be differentiated from other diseases that cause fever, abdominal pain, cough, jaundice, hepatomegaly, anorexia, nausea, vomiting, and pale or dark stools such as pyogenic liver abscess, fungal liver abscess, echinococcal cyst, and hepatocellular carcinoma.

# Epidemiology And Demographics
Amoebiasis is the second leading cause of death worldwide from parasitic disease.500 million people are infected with Entamoeba histolytica every year. 50 million individuals develop liver abscess and colitis and results in death in 40,000-100,000 individuals annually. Of all cases of amoebiasis, 3% to 9% of patients reported to have amoebic liver abscess. It most commonly occurs in 20 to 45 years age.

# Risk Factors
Common risk factors in the development of amoebic liver abscess include alcoholism, pregnancy, malnutrition, old age, immunosupression (including HIV), a recent travel to a tropical region, steroid use, hypoalbuminemia, chronic infection,tuberculosis, syphilis, splenectomy, malignancy, and homosexuality.

# Screening
According to the U.S. Preventive Service Task Force (USPSTF), there is insufficient evidence to recommend routine screening for Entamoeba histolytica infection.

# Natural history, Complications And Prognosis
If left untreated, amoebic liver abscess may disseminate to other organs leading to death.The complications of amoebic liver abscess develop due to rupture of the abscess into the abdomen or chest cavity. The complications include  peritonitis, pericarditis / pneumopericardium / tamponade, pleuropulmonary / pneumothorax (the right lung and pleural space are frequently effected because of their proximity to the liver), obstructive jaundice, bacterial superinfection, cutaneous fistulization of chest and abdominal wall, inferior vena cava obstruction, hemobilia / thoracobilia, internal fistulization, systemic inflammatory response syndrome, Venous and arterial thrombosis.Prognosis is good with treatment. Patients who are treated have high chance of complete recovery or minor complications.

# Diagnosis

## History And Symptoms
Specific areas of focus when obtaining a history from the patient include history of recent travel to or resident of endemic areas, time of onset (duration of symptoms <14 days), history of dysentery within the previous few months, fever and abdominal pain.Symptoms of amoebic liver abscess include moderate to severe abdominal pain, malaise, loss of appetite, sweating, weight loss, epigastric pain (Commonly seen in left lobe abscesses), fever (high fever with chills is suggestive of secondary bacterial infection), anorexia, pleuritic chest pain, Cough with or without expectoration and chest pain (may be due to abscess rupture into the pleural cavity), jaundice, confusion, abdominal distension, nausea and vomiting, diarrhea and constipation

## Physical Examination
Common physical examination findings associated with amoebic liver abscess may include sweating and ill appearing patient with weight loss, fever with chills, tachycardia, yellowish discoloration of skin (jaundice), icteric sclera, reduced breath sounds or crepitations at right lung base may be heard, chest tenderness on palpation and audible pericardial friction rub. Hepatomegaly with point tenderness over the liver, in the intercostal spaces, or below the ribs is a typical finding Epigastric mass if left lobe is involved. Abdominal guarding or rebound tenderness, dullness on percussion, abdominal distension and absent bowel sounds are other findings.

## Laboratory findings
Laboratory tests consistent with diagnosis of amoebic liver abscess include complete blood count, ESR, C-reactive protein, liver function tests, and stool examination.

## ECG
There are no ECG findings associated with amoebic liver abscess.

## Chest X Ray
Chest X ray findings include pleural effusion, elevated right hemidiaphragm, atelectasis, and types of hepatic abscesses.

## CT Scan
CT scan findings of amoebic liver abscess include shape of abscess, varying sizes ranging from 4 cm to 12 cm, well defined lesion with attenuation values indicating the presence of complex fluid, wall enhancement, peripheral zone of edema with wall thickness around 3-15 mm, the central abscess cavity with septations and/or fluid-debris levels, and gas in the abscess if associated with hepatobronchial fistula or a hepatocolic fistula.

## MRI
MRI findings of amoebic liver abscess include T1 weighted images with homogenous low signal intensity (signal homogeneity within the abscess can be present more often on T1- than on T2-weighted images) and T2 images are generally homogeneous with high signal intensity and perilesional edema may be seen in half of the cases.

## Ultrasonography
Ultrasound is the gold standard technique for the diagnosis of amoebic liver abscess. The intrahepatic ultrasound findings include homogenous hypoechoic areas that can be single or multiple with round edges, round or oval in shape and variable size (around 2-6 cm in diameter), an incomplete rim of edema, location near liver capsule, margin of abscess tends to be nodular in around 40% of cases and smooth in 60% of cases, internal septations may be present in 30% of cases, and focal intrahepatic biliary dilatation peripheral to an abscess may be present. The extra hepatic findings include pleural effusion, perihepatic fluid collection, gastric or colonic involvement and retroperitoneal extension.

## Other Imaging Studies
Other imaging studies include technitium-99m liver scanning, gallium citrate scan and hepatic angiography.

## Other Diagnostic Studies
Other diagnostic studies include microscopic techniques, culture methods, isoenzyme analysis, antibody detection tests, antigen detection tests, immunochromatographic assays and DNA based diagnostic tests.

# Treatment

## Medical Therapy
Indications for medical management of amoebic liver abscess are all non-complicated abscesses, no compression effect, and no features of rupture or impending rupture. Treatment of intraluminal infection include iodoquinol, metronidazole, tinidazole, and paromomycin.

## Surgical Therapy
Surgery is not the mainstay of treatment. Percutaneous needle aspiration and surgical open drainage are the surgical methods used to treat amoebic liver abscess.

## Primary Prevention
Primary prevention of amoebic liver abscess include drinking purified water and eat well-cooked food while traveling in tropical countries with poor sanitation, boiling water before drinking, raw vegetables must be washed with soap and then soaked in vinegar for 15 min before they can be eaten, and screening of family members to prevent spread of disease:

## Secondary Prevention
The secondary prevention of amoebic liver abscess includes long-term follow-up after treatment. Ultrasound is the main imaging technique used during the follow-up period. The mean time for the disappearance of sonographic features (hypoechoic lesions) is 6-9 months.