Clinical and Radiologic Diagnosis of Liver Abscess
There are three main types of liver abscess: pyogenic, amebic, and fungal. Pyogenic abscesses
occur most often in the United States and are usually polymicrobial. Pyogenic liver abscesses
occur by direct extension from infected adjacent structures or by hematogenous spread via the
portal vein or hepatic artery. Clinical presentation may be insidious, with fever and right
upper quadrant pain being the most common presenting complaints. The right lobe of the liver
is more often affected secondary to bacterial seeding via the blood supply from both the
superior mesenteric and portal veins. Untreated, the disease is usually fatal, but with prompt
abscess identification and then antibiotic administration and drainage, mortality is
significantly decreased (15).
Both CT and ultrasound can be used for diagnosis and follow-up of liver abscess as well
as for guiding percutaneous drainage. The CT appearance of a liver abscess is a round, well-
defined hypodense mass that may contain gas centrally (Fig. 6). A commonly seen finding is
the “cluster sign” representing a conglomerate of small abscesses coalescing into a single large
cavitating lesion. An associated capsule or septations may be present, which enhance with IV
contrast administration. Secondary findings include right pleural effusion and right lower lobe
atelectasis. On ultrasound, the lesion is usually spherical or ovoid with hypoechoic, irregular
walls. Centrally, the abscess may be anechoic or less often hyperechoic or hypoechoic,
depending on the presence of septa, debris, or necrosis (3,7).
Figure 5 CT scan of the pelvis in a 91-year-old
male with known prostate cancer demonstrates
a large, slightly heterogeneous prostate (large
arrow) protruding into the bladder base (small
arrow).Figure 6 CT scan of the abdomen demon-
strating an abscess in the right hepatic lobe
(arrow) in a 36-year-old male with fever and
abdominal pain following recent laparoscopic
appendectomy for perforated appendicitis.80 Luongo et al.