An abscess is a local accumulation of pus in an organ. As this accumulation of pus in the beginning is contained in a cyst-like structure, it can be difficult to diagnose. However, as time goes on the pathogens in this abscess cavity are exerting pressure and are eating their way more and more into the healthy surrounding liver tissue.
A CT scan will visualize of a liver abscess. The end result can be that an overwhelming infection suddenly can gain entrance into the blood stream at which point the patient gets extremely sick with septicemia.
A liver abscess can originate from a variety of conditions as follows.
•Bile ducts can get infected when a gallstone is present and the infection can travel against the bile flow into the liver tissue (=ascending cholangitis).
•Bacteria can reach the liver through the systemic circulation in the case of septicemia (blood poisoning with bacteria).
•Another mode of transmission is via the portal vein system in the case of appendicitis or diverticulitis, where the pus from an appendicitis or from a case of diverticulitis of the colon reaches the liver through the portal vein system.
•Finally, sharp or blunt trauma can cause an abscess. In the case of a stab wound or a gun shot wound the bacteria are directly introduced into the liver tissue.
In the case of blunt trauma from a blow to the upper abdomen a hematoma forms on the surface or inside the liver. A hematoma is a localized blood collection, which tends to attract bacteria that happen to travel through the blood. Normally they are immediately removed by white blood cells. However, in a hematoma, there is no circulation of white blood cells, but blood serves as an ideal growth medium for the bacteria, which by chance have found their way into the liver. After they have multiplied enough, the digestive enzymes eat a cavity into the liver tissue, where pus forms and a membrane demarcates it from the healthy tissue. This forms the wall of the abscess.
The pathogens that cause liver abscesses are quite varied. Common bacteria are streptococci or staphylococci, which usually originated systemically through the blood stream. Abscesses due to the infected biliary tract grow E.coli and Klebsiella bacteria. E. coli and anaerobic bacteria are usually isolated from an intraabdominal infection that was transmitted via the portal vein system. An amebic abscess from Entamoeba histolytica( which is a parasite) has a better prognosis than the bacterial abscesses and responds well to appropriate medication.
When there are several abscesses in the liver, the symptoms are acute with acute right upper abdominal pain, vomiting, nausea, weight loss, a fever and weakness. The patient might also experience right chest pain( due to pleuritic irritation)and might be jaundiced, particularly with biliary tract disease. In other cases with a single liver abscess it might take several weeks to see symptoms develop. There might be only a fever, malaise, weight loss and nausea. Then gradually the other symptoms develop as more and more pus is produced in the abscess cavity.
Before treatment can be instituted, the surgeon will want to be absolutely sure where the abscess is. A CT scan or MRI scan are the most sensitive tests, but an ultrasound of the liver can detect abscesses of more than 2 cm (=0.8 inch) in diameter.
The imaging studies are in addition to the normal basic history and physical examination. Blood tests would also be useful with high white blood cell readings and elevated liver enzymes.
Treatment depends on the pathogen, which has caused the abscess. For instance, an amebic abscess will respond well to chemotherapy with metronidazole, emetine or chloroquine. Other (bacterial) abscesses will be treated with the appropriate antibiotic first and often with percutaneous needle aspiration pus can also be sucked out. Surgery is reserved only for those patients, where these other measures did not resolve the abscess. Usually for prevention of recurrence patients are put on antibiotics for several weeks.
The abscess can rupture or spread locally. This can cause such things as a subphrenic abscess( an abscess between the liver and the right diaphragm), a rupture into the right pleural cavity, into the right lung, bleeding into the abscess, rupture of the abscess into the peritoneal cavity with development of generalized peritonitis and septicemia. Despite the best therapy the mortality rate of a liver abscess is still between 10% and 30%.
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