Pyogenic liver abscess caused by Fusobacterium nucleatum with an inflammatory scar in the abdominal cavity

Pyogenic liver abscesses generally occur secondary to spread from active infective lesions. We report a rare case of liver abscess in a patient without a clear source of infection. A 19-year-old man was diagnosed as having a liver abscess after investigations when he presented with chief complaints of fever and lethargy. Fusobacterium nucleatum was detected in the pus culture taken from the abscess that was drained. His condition improved with antibacterial treatment. Further examination of the gastrointestinal tract suggested that the infection had tracked through the portal vein from a scar between the rectal sigmoid and the appendix. Laparoscopic adhesiolysis and appendectomy were performed to treat the same. Fusobacterium can be identified early by Gram staining of pus from the liver abscess, which is useful for treatment. In young people with pyogenic liver abscess due to Fusobacterium nucleatum who are not immunocompromised, examination of the gastrointestinal tract should be considered to determine a cause.