Contrast-enhanced ultrasound in different stages of pyogenic liver abscess.

To enable sonographic classification of different stages of pyogenic liver abscesses, sonographic findings in 86 patients with 113 pyogenic liver abscesses were retrospectively analyzed and compared with established pathomorphologic descriptions of the disease. The typical findings in contrast-enhanced ultrasound were sub-segmental hyperemia (93/113, 82%) and necrosis with a hyperemic margin (109/113, 96%) in the arterial phase and a washout of liver tissue surrounding necrosis in the late phase (101/113, 89%). Four different sonomorphologic stages of pyogenic liver abscess were identified. Stage I was defined by focal inflammation without necrosis (n = 2); stage II by focal clusters of micro-abscesses appearing to coalesce (n = 41); and stage III by a single cavity with or without capsule (n = 64). Stage IV was defined as numerous small abscesses scattered all over the liver (n = 6). The results indicate that contrast-enhanced ultrasound is suitable for classifying different stages of pyogenic liver abscesses. Knowledge of the described morphologic patterns influences therapeutic decisions and helps distinguish abscesses from other liver masses.