Ultrasound analysis of solid-appearing abscesses.

A retrospective review of 96 abdominal abscesses yielded 11 cases (9%) that were diffusely echogenic on sonograms and that stimulated findings of solid lesions. Sonographic features of these abscesses were analyzed and compared with features of 78 cases of hepatic metastasis. An abscess was considered solid appearing when it contained diffuse internal echoes that were distributed over 90% of the abscess cavity. The visualized internal echoes were of low to medium amplitude, and were generally similar to the normal echogenicity of the parenchymal organs, such as the liver, spleen, or uterus. Distal acoustic enhancement was seen in 91% of the solid abscesses, and it was not seen in hepatic metastases. A distinct echogenic wall was present in 64% of the abscesses (subacute and chronic lesions), but this occurred in less than 4% of metastases. Thin peripheral halos inside or outside of and adjacent to the abscess wall were seen in 36% of abscesses. The peripheral halos seen in metastases were wider and not associated with an echogenic wall. The diagnosis of a diffusely echogenic abscess and differentiation from a neoplasm is possible when the sonographic findings of acoustic enhancement, thin peripheral halo, and echogenic abscess wall are present.