Very early stage :
At this stage, the differential diagnosis of fat spared area in a fatty liver or an early neoplastic lesion have to be considered.
Recently formed amoebic abscesses :sonolucent or an hypoechoic area usually with fine internal echoes. Because of the liquefaction, there is associated posterior acoustic enhancement. The cavity may be round, oval or branching. The walls of the abscess at this stage are usually not very thick and sometimes the demarcation between the wall and the surrounding tissue can be poor. Sometimes the walls may be thicker and these may be seen as shaggy, ill-defined echogenic areas along the walls (see Picture). It is at this stage of the abscess that aspiration may be required. Small amount of air in the abscess because of secondary infection or following an aspiration is seen as highly reflective dots.
It is at this stage of the abscess that differential diagnosis of a cyst in the liver, a cyst with haemorrhage, cystic metastatic deposit or sometimes a hydatid cyst and haematoma are to be considered.
Abscesses of some duration :
Healing Stage :The abscess heals, the liquid contents dry up, which has been described as putty appearance. On ultrasound it is seen again as a lesion with thick walls fairly echogenic as compared to surrounding organs. This shadow can be seen on ultrasound for a long time, even years. It is usually at this stage that the differential diagnosis of a neoplasm, haemangioma or granuloma in liver come into picture.