The second most common mechanism is bacterial translocation through the portal venous system. E. coli is commonly isolated and is frequently spread from intra-abdominal infections such as appendicitis leading to pylephlebitis. As the diagnosis and management of appendicitis has improved, the incidence of appendicitis causing a PLA has decreased.
PLA should be cultured to guide therapy and catheter drainage may be required. However, common organisms causing liver abscess should also be considered when selecting initial antibiotic therapy as cultures are frequently affected by previous antibiotic exposure or imprecise culturing techniques. Blood cultures should be obtained, and empiric therapy with a beta-lactam/beta-lactamase inhibitor or third-generation cephalosporin plus metronidazole should be started thereafter.
Entamoeba histolytica. E. histolytica, an anaerobic parasite that can lead to amoebic dysentery and liver abscess, affects upwards of 50 million people worldwide, predominantly in India and sub-Saharan Africa. Travel to an endemic area for longer than 1 month carries a high risk of transmission, though cases have been described with less than a week of exposure.