INTRA-ABDOMINAL INFECTIONS: LIVER ABSCESS
Pyogenic liver abscesses are relatively uncommon, with an incidence of 0.005% for all hospital admissions. The most common cause of pyogenic liver abscess is biliary tract disease leading to ascending cholangitis. Other routes of infection include the portal vein (draining an intraabdominal infection), the hepatic artery (with systemic bacteremia), direct extension from a contiguous focus of infection (e.g., cholecystitis, subphrenic abscess), or penetrating trauma to the liver. One quarter of all hepatic abscesses are cryptogenic, with no direct cause found.
The etiologic organisms are primarily enteric bacteria, with E. coli and K. pneumoniae being most common. Enterococci and viridans streptococci are also likely, particularly in cases of polymicrobial abscesses. Two thirds of liver abscesses are polymicrobial, and one third involves anaerobes. S. aureus is more common in children and in patients with bacteremia. Entamoeba histolytica is responsible for 10% of liver abscesses.
A minority of patients present with the classic triad of fever, jaundice, and right upper quadrant pain (Charcot’s triad). More often, fever and constitutional symptoms, including malaise, fatigue, anorexia, and weight loss, are present. Patients often have an enlarged liver and may have point tenderness. Suspicion of an amoebic liver abscess may be elicited by a history of travel or diarrhea, although impaired immunity also appears to be a risk factor in the absence of a travel history.
Peripheral leukocytosis is common, as are elevated serum alkaline phosphatase levels, usually without an elevation in bilirubin. Stool examination to look for E. histolytica trophozoites or cysts is usually not helpful, since most patients do not have detectable parastites in the stool. Serologic testing with enzyme immunoassays specific for E. histolytica is often useful.
Computed tomography is the most accurate imaging technique in the diagnosis of liver abscess, with a sensitivity of 95% or greater. Ultrasonography is the study of choice in patients with suspected biliary tract disease or in patients who must avoid intravenous contrast agents. An amoebic liver abscess is more likely to be solitary than pyogenic abscesses and is usually limited to the right lobe of the liver.
Treatment of a pyogenic liver abscess requires drainage as well as antibiotics. The initial procedure of choice is percutaneous drainage, which has a success rate of almost 90%. Surgical drainage is usually reserved for cases that do not resolve with the percutaneous approach. Empiric therapy for pyogenic liver abscess is the same as that recommended for secondary peritonitis. Amoebic liver abscess can usually be treated with medical management alone. Metronidazole is the drug of choice and is given as 750 mg three times a day for 10 days. This should be followed by a luminal agent (typically paromomycin or diloxanide furoate) to treat asymptomatic colonization.
*97/348/5*
