HEPATIC ABSCESS

Abscesses in the liver may be due to Entamoeba histolytica or to various bacterial organisms. Clinical differentiation between the two types on the basis of such features as height of the temperature, leucocytosis or local pain and tenderness is notoriously unreliable. Amoebic liver abscesses are characteristically single and located in the right lobe and may be extremely large and . Most patients do not give a history consistent with preceding or current amoebic dysentery. An enlarged, tender liver, elevated diaphragm on chest X-ray, leucocytosis and elevated serum alkaline phosphatase levels are usually observed. Radioisotope scanning, computed tomography and ultrasonography are valuable for demonstrating the abscess. A serological test for amoebiasis is almost always positive in amoebic liver abscess. Occasionally, multiple amoebic abscesses are present and . The abscess cavities contain whitish, incompletely liquified, necrotic material which is sharply distinct from the normal liver tissue, and thick, brownish, odourless, liquified material consisting of necrotic liver tissue, inflammatory cells, and small or large numbers of amoebae . This material is regarded by some as resembling anchovy paste. Medical therapy with metronidazole or other drugs is usually effective and surgical drainage is rarely required.

Bacterial liver abscesses may occur secondary to nearby infection in the biliary tract, or the organisms may reach the liver via the portal vein (from intra-abdominal infections such as appendiceal abscess) or the systemic circulation. They are more likely than amoebic abscesses to be multiple. If the source of the abscess is infection in the biliary tract, the most common aetiological agents are E. coli and other members of the Enterobacteriaceae, including salmonella. If the infection has reached the liver via the portal vein, anaerobic bacteria, with or without aerobic species, are usually found. Streptococci of the S. intermedius (S. milleri) group are found in up to 80% of the lesions. Radionuclide scanning , computed tomographic scanning ( and ) and ultrasonography are valuable for confirming the presence of suspected liver abscesses. Percutaneous catheter drainage, using computed tomography to achieve precise placement of the catheter , has obviated the need for surgical drainage in most cases of bacterial liver abscess. When multiple abscesses are present it may be necessary to drain several of the largest cavities. Treatment with an antibiotic effective against the infecting organisms should be administered for from one to several months. Amoebic liver abscesses are sometimes secondarily infected with bacteria; this type of combined infection may be very difficult to diagnose.