ESSENTIALS OF DIAGNOSIS
Fever, right upper quadrant pain, jaundice.
Often in setting of biliary disease, but up to 40% are “cryptogenic” in origin.
Detected by imaging studies.
The incidence of liver abscess is 3.6 per 100,000 population in the United States and has increased since the 1990s. The liver can be invaded by bacteria via (1) the bile duct (acute “suppurative” [formerly ascending] cholangitis); (2) the portal vein (pylephlebitis); (3) the hepatic artery, secondary to bacteremia; (4) direct extension from an infectious process; and (5) traumatic implantation of bacteria through the abdominal wall. Risk factors for liver abscess include older age and male sex. Predisposing conditions and factors include presence of malignancy, diabetes mellitus, inflammatory bowel disease, and cirrhosis; necessity for liver transplantation; endoscopic sphincterotomy; and use of proton pump inhibitors. Statin use may reduce the risk of pyogenic liver abscess. Pyogenic liver abscess has been observed to be associated with a subsequent increased risk of gastrointestinal malignancy and hepatocellular carcinoma.
Acute cholangitis resulting from biliary obstruction due to a stone, stricture, or neoplasm is the most common identifiable cause of hepatic abscess in the United States. In 10% of cases, liver abscess is secondary to appendicitis or diverticulitis. At least 40% of abscesses have no demonstrable cause and are classified as cryptogenic; a dental source is identified in some cases. The most frequently encountered organisms are E coli, Klebsiella pneumoniae, Proteus vulgaris, Enterobacter aerogenes, and multiple microaerophilic and anaerobic species (eg, Streptococcus anginosus [also known as S milleri]). Liver abscess caused by virulent strains of K pneumoniae may be associated with thrombophlebitis of the portal or hepatic veins and hematogenously spread septic ocular or central nervous system complications; the abscess may be gas-forming, associated with diabetes mellitus, and result in a high mortality rate. Staphylococcus aureus is usually the causative organism in patients with chronic granulomatous disease. Uncommon causative organisms include Salmonella, Haemophilus, Yersinia, and Listeria. Hepatic candidiasis, tuberculosis, and actinomycosis are seen in immunocompromised patients and those with hematologic malignancies. Rarely, hepatocellular carcinoma can present as a pyogenic abscess because of tumor necrosis, biliary obstruction, and superimposed bacterial infection (see Chapter 39-06). The possibility of an amoebic liver abscess must always be considered (see Chapter 35-07).
The presentation is often insidious. Fever is almost always present and may antedate other symptoms or signs. Pain may be a prominent complaint and is localized to the right upper quadrant or epigastric area. Jaundice, tenderness in the right upper abdomen, and either steady or spiking fever are the chief physical findings. The risk of acute kidney injury is increased.
Laboratory examination reveals leukocytosis with a shift to the left. Liver biochemical tests are nonspecifically abnormal. Blood cultures are positive in 50–100% of cases.