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Amoebic liver abscess
(Tropical abscess, dysenteric abscess)

is the separate or confined inflammation of pus. It is of two types:
  • Pyogenic caused by pyogenic flora
  • Parasite abscesses caused by Entamoeba Histolytica.
Incidence is high in Asian countries and in places where sanitation and mental institution is poor. All patients with amoebic abscess are younger than their counterpart than pyogenic abscess.

Etiology:
Amoebic colitis leads to amoebic hepatitis which is followed by the amoebic liver abscess. The condition is always secondary to amoebic ulcers on colonic wall. It may occur in the digestive tract with water and food. Entamoeba Histolytica forms lesions in the colonic wall and then enters into the venules and thereafter pass up along the inferior mesenteric vein followed by splenic vein to the portal vein and then finally reaches the liver.

Pathology:
In the liver they may regenerate or continue migration to the adjacent organs (structures). If they multiply, they live at the expense of liver cells. They cause multiple foci of liquefactive necroses in the liver substance. Coalescence of these necrotic areas forms the abscess. Most favourable site of an abscess is the postero-superior surface of the right lobe of liver. In 70% the abscess is solitary and in 30% it is in the multiple forms.

Characteristically pus is chocolate coloured as it results from degenerating liver substance and blood, is viscid and glary popularly called Anchovy Sauce. In many cases pus is green because of its bile contents and in rare cases the abscess is creamy.

Primarily the wall is composed of the necrotic liver tissue and shaggy in nature. Later the wall becomes deposited with fibrous tissue making it as if it is a capsule. Perihepatitis occurs early and liver may become fixed to diaphragm and abdominal wall by adhesions. Wall of abscesses and the surrounding liver tissue always contain Entamoeba. The abscess gradually enlarges upward if left untreated; it reaches to the surface of liver and burst. Usually ruptures in:
  • Right lung
  • Peritoneal cavity
  • Right pleural cavity
  • A hollow viscous organ (e.g. colon)
  • On skin surface.
Occasionally under medication it undergoes resolution.

Signs and Symptoms:
  • Pain is worsened by movement and may radiate to the shoulder due to diaphragmatic adhesion of the abscess.
  • Fever is nocturnal in nature with chills, rigors and profuse sweating.
  • Malaise
  • Weight loss
  • Nausea
Physical signs:
  • Tenderness over right upper quadrant
  • Progressive anaemia
  • Rigidity over right hypochondrium
  • Hepatic enlargement
  • Pleural dullness by percussion
  • Jaundice
  • Right lung may present rales and rhonchi
Investigations:
Radiography:
Irregularly elevated and fixed dome of diaphragm
Pleural effusion

Liver scanning: US and CT scans are useful but it has disadvantages because it is impossible to detect pus which is less than 2cm
Aspiration
Stool examination: for Entamoeba
Blood examination: anaemia and leucocytosis

Treatment:
  • Metronidazole (100mg for 14 days) is drug of choice. If he superinfection results then antibiotics are added
  • Drainage: (open and closed) Drainage of the abscess from the cavity may be performed as transcutaneously after opening of the abdominal cavity. There are two methods:
    1. Transabdominal
    2. Transthoracic
Transthoracic approach is done as follows:
Approach to the liver, thorax and transthorax after the skin is excised. Then bluntly separate the fibers of the muscles. The incision may be made under 9th costal rib between middle and posterior Axilliary line. After we remove 9th costal rib subperiostically. Then here we can directly dissect the peritoneum. Via this way we the make approach to the liver. Here we must remember that transabdominal approach is of choice.

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This article has been written by Dr. M. Javed Abbas.
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21:06 21/12/2002