LIVER ABSCESS



Pyogenic Liver Abscess. Pyogenic liver ab­scess represents a macroscopic collection of pus within the liver parenchyma due to bacterial in­fection. Liver abscess is an uncommon disorder in the United States, a surprising observation in view of the rich blood supply of the liver and its position upstream from the bacteria-laden intes­tine. The most common predisposing cause of py­ogenic liver abscess is biliary tract disease, es­pecially bile duct obstruction with cholangitis or acute cholecystitis. Less frequent predisposing factors include infection in areas drained by the portal system (e.g., appendicitis and diverticuli­tis), direct extension from subphrenic or perine­phric abscesses, abdominal trauma, and infection in necrotic tumor deposits. Abscesses maybe sin­gle or multiple, large or small. Enteric flora such as Escherichia coli or Klebsiella and pyogenic gram-positive cocci such as Staphylococcus au­reus are the most common causes of pyogenic liver abscesses, although anaerobes either alone or in combination with aerobes may account for up to 50 per cent of all pyogenic abscesses. He­patic abscesses generally present as a febrile ill­ness lasting days to weeks, often associated with right upper quadrant abdominal pain and tender­ness. Pulmonary symptoms, including cough and pleuritic chest pain as well as pulmonary rales and a pleural effusion, are seen in 20 to 40 per cent of cases. Jaundice may be seen in up to 20 per cent of patients, usually due to concomitant biliary disease. Laboratory tests are generally not helpful, although most patients exhibit a leuko­cytosis and elevated serum alkaline phosphatase activity. Lesions can be localized by radionuclide scan, ultrasound, or computed tomography (see Chapter 37), and the diagnosis is established by percutaneous or surgical aspiration of material for Gram’s stain and culture (including anaerobic cul­ture techniques). Blood cultures, which are pos­itive in up to 40 per cent of patients, should also be obtained prior to antibiotic treatment. Broad-spectrum antibiotic therapy directed against anaerobes and aerobes should be initiated imme­diately and, once culture results are available, ap­propriately tailored according to the sensitivities of the isolated organisms. After a diagnostic as­piration, most abscesses can be treated with an­tibiotics alone for four to six weeks or in combi­nation with percutaneous drainage. Surgical therapy is generally necessary for those patients with concomitant intra-abdominal sepsis or bili­ary tract obstruction. Complications of pyogenic abscesses include sepsis, pleuropulmonary in­volvement via direct extension or embolization, and peritonitis due to abscess rupture. The mor­tality of treated abscesses is high; however, that of untreated abscesses is 100 per cent.
Amebic Liver Abscess. Amebic liver abscess is rare in the United States, but common in parts of the world where sanitation is poor. Amebic liver abscesses arise in individuals who harbor ameba in the colon, although the colonic infection may be asymptomatic. The clinical and laboratory fea­tures of amebic liver abscess are quite similar to those of pyogenic liver abscess, and the two dis­orders can be definitively distinguished only by examination and culture of aspirated abscess con­tents (amebic abscesses contain “anchovy paste” material that is free of bacteria) and serological tests. Because ameba are found only at the edge of the abscess, it is important to examine the last few drops of aspirated material for organisms. In­direct hemagglutination and gel diffusion precip­itin tests for ameba are positive in over 90 per cent of individuals with amebic abscesses, although they may be negative when the patient first pre­sents. Medical therapy is curative and should be instituted promptly in all patients suspected of having an amebic abscess. Metronidazole (750 mg t.i.d. for 10 days) followed by diiodohydroxyquin (650 mg t.i.d. for 20 days) to eliminate intestinal cysts are the drugs of choice, although the com­bination of dehydroemetine and chloroquin fol­lowed by diiodohydroxyquin is also effective. Surgical drainage is usually unnecessary unless the abscess has ruptured into the pleural, peri­cardial, or peritoneal space.





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