Sonographic features of amebic and pyogenic liver abscesses: a blinded comparison.

We blindly compared the sonographic findings in amebic (112 lesions) and pyogenic (30 lesions) liver abscesses. Two sonographic features were significantly more prevalent in amebic abscesses: the lesions had a round or oval shape and the lesions had an echogenicity that was lower than that of normal liver and were internally homogeneous on high-gain scans. Amebic abscesses were round or oval in 92 instances (82%), while 18 pyogenic abscesses (60%) (p less than .01) had these shapes. Fifty-nine (58%) of 101 amebic abscesses displayed low echogenicity and homogeneous internal echoes with high-gain settings compared with nine (36%) of 25 pyogenic abscesses (p less than .04). Despite these different sonographic patterns, image findings alone were inadequate in distinguishing pyogenic from amebic liver abscesses. However, when the sonographic findings were coupled with clinical and laboratory data, a correct diagnosis was possible in 83 (86%) of 96 patients with amebic abscess. It appears that, although some sonographic features of amebic abscess differ from those of pyogenic abscess, these differences are not sufficient to allow a specific diagnosis on the basis of sonography alone. Sonography can expedite abscess detection and, when coupled with clinical and laboratory data, can aid in differentiating pyogenic from amebic liver abscesses.