Mimic of Liver Abscess
A nonliquefied abscess (particularly fromKlebsiellaspecies) can sometimes be confused with
hepatic tumor such as hepatocellular carcinoma (HCC) or metastastic disease from gastroin-
testinal primary tumors or vice-versa (Fig. 7), particularly when solitary. Like abscess, these
also appear more often on the right side of the liver when solitary. A helpful differentiating
factor is that most cases of HCC occur in patients with underlying cirrhosis (3).
On ultrasound, the mass appears mixed in echogenicity and demonstrates increased
vascularity on color Doppler interrogation. The appearance on portal venous phase (i.e.,
routine delay following IV contrast) CT is usually that of a hypodense mass with or without
necrosis. The tumor may have a capsule, which enhances after contrast administration. Portal
vein thrombosis occurring in conjunction with liver abscess is clinically and radiologically
difficult to differentiate from tumor thrombus in HCC. HCC demonstrates characteristic
enhancement patterns on multiphasic CT scans performed with at least both arterial and portal
venous phases, which aids in diagnosis and differentiation from other entities. The tumor is
heterogeneous on arterial-phase CT (or MR) imaging, intermixed with areas of hypoperfusion
from portal vein occlusion by tumor thrombus. There is then washout of contrast on the portal
venous phase, as the tumor is supplied almost exclusively by the hepatic artery, and, if
performed, on the delayed phase (3,16,17).
MR can also be used, although it is mostly reserved for those cases that are indeterminate
on CT or when there is a contraindication to iodinated contrast for CT and IV gadolinium can
be administered for MR. On T1-weighted imaging, HCC is typically hypointense, whereas on
T2-weighted images, it is usually somewhat hyperintense. With gadolinium administration,
the enhancement pattern varies from central to peripheral and from homogeneous to rim
enhancing. Also on T2-weighted imaging, the hyperintensity surrounding an abscess is
typically much greater than that which would be seen for HCC (3,16,17).
Clinical and Radiologic Diagnosis of Splenic Abscess
Splenic abscess is a rare entity with a high mortality rate. The most common etiology is
hematogenous spread of infection from elsewhere in the body. Alcoholics, diabetics, and
immunocompromised patients are most susceptible. There are a diverse array of pathogens,
including bacteria (aerobic and anaerobic) and fungi (18).
Diagnosis cannot be made solely through history and physical examination. CT is the
standard imaging modality for diagnosis and therapeutic drainage planning. CT findings
include a low-attenuation, ill-defined mass within the splenic parenchyma. As with abscesses
elsewhere in the abdomen and pelvis, there may be gas or an air-fluid level. There is no
enhancement of the central portion after IV contrast administration, although as with hepatic
abscesses, there is often perilesional enhancement as well as surrounding edema. There may be
Figure 7 Non-enhanced CT scan of the abdo-
men in a 77-year-old male with colon cancer
demonstrating multiple low-density lesions
throughout the liver (stars), representing metas-
tases.Radiology of Infectious Diseases and Their Mimics in Critical Care 81