To examine the resolution of liver abscesses, a prospective ultrasonographic follow-up study was conducted in 51 patients, each with a solitary abscess (26 pyogenic and 25 amebic) which had been treated successfully by non-surgical measures. The rate of complete abscess resolution for each of the initial 6 months was 0%, 5%, 10%, 23%, 30%, and 30% in the amebic group; and 20%, 54%, 77%, 89%, 94%, and 94% in the pyogenic group. The absorption volume of the pyogenic group in the first month was also greater than that of the amebic group (3.0 ± 5.0 ml/day vs. 1.1 ± 0.8 ml/day, P < 0.05). The resolution ratio of pyogenic and amebic liver abscesses in the first month was 74% ± 38% and 36% ± 23%, respectively. In 3 patients in the amebic group, the abscess was still detectable 2 years after treatment.
These results suggest that pyogenic liver abscesses resolve more rapidly than amebic abscesses. These findings should be considered in the differential diagnosis of asymptomatic space-taking lesion in the liver.