inflammatory stranding of the perisplenic fat. Ultrasound demonstrates a hypoechoic lesion
that may contain internal septations and low-level internal echoes, representing either debris
or hemorrhage. There is no blood flow within the central areas on Doppler interrogation (3,19).
Mimic of Splenic Abscess
Splenic infarct may have a similar clinical presentation, including fever, chills, and left upper
quadrant pain. Differentiating the two entities is important, as an infarct can be managed
conservatively, whereas abscess requires antibiotic therapy and possibly drainage. On CT, a
splenic infarct is classically a peripheral, wedge-shaped low-attenuation region after IV
contrast administration (Fig. 8). However, the lesion may be rounded, similar to an abscess, or
irregular. Lack of mass effect on the splenic capsule may be a helpful differentiating factor
from abscess. Further complicating matters, in patients with septic emboli (e.g., from
endocarditis), the CT findings may be identical to those of bland infarction (e.g., from atrial
fibrillation), and differentiating between these two entities is difficult to impossible without
clinical correlation (3,19).
Unlike abscess, on follow-up cross-sectional imaging, an infarct should become better
demarcated and eventually resolve, leaving an area of fibrotic contraction and volume loss. A
deviation from this expected course suggests a complication such as hemorrhage or
superimposed infection (19).
Clinical and Radiologic Diagnosis of Cholangitis/Calculous Cholecystis
Acute infection of the biliary system is often associated with biliary obstruction from
gallbladder calculi. Obstruction leads to intraluminal distention, which interferes with blood
flow and drainage, predisposing to infection. The most common pathogens are E. coli,
Klebsiella, enterobacter, enterococci, and group D streptococci. Elderly patients are particularly
predisposed to infection (20).
On ultrasound, cholangitis appears as thickened walls of the bile ducts, which may be
dilated and contain pus or debris. Visualization of an obstructing stone increases diagnostic
certainty, although MR cholangiography (see below) is more accurate for identification of such
stones. The ultrasound criteria for acute cholecystitis include cholelithiasis and a sonographic
Murphy’s sign, considered the most sensitive findings, with additional findings of a thickened
gallbladder wall (>3 mm) and pericholecystic fluid (Fig. 9A) (3,20,21).
CT is somewhat less sensitive due to a minority ofgallstones being calcified and therefore
radiopaque. CT findings include a distended gallbladder, gallbladder wall thickening, perichole-
cystic fat stranding and calcified gallstones, when present. There is also mural enhancement with
IV contrast administration (Fig. 9B). Complications including gangrenous changes in the wall, with
heterogeneity of enhancement, and pericholecystic abscess, are also identifiable on CT (3,21).
Figure 8 CT scan of the abdomen in an 82-
year-old male demonstrating multiple peripheral,
wedge-shaped, low-density lesions in a mildly
enlarged spleen (arrows) that are acute and
subacute infarcts.82 Luongo et al.