9%20ECOGRAFIA%20ABDOMINAL%20COMO%20CUANDO%20DONDE

94
ABDOMINAL ULTRASOUND
The ultrasound appearances of HCC vary from
hypo- to hyperechogenic or mixed echogenicity
lesions (Fig. 4.18). It is often particularly difficult
to locate small HCCs in a cirrhotic liver which is
already coarse-textured and nodular. CT and MRI
may be useful in these cases. 10,11
These lesions may be solitary or multifocal.
Colour and spectral Doppler can demonstrate
vigorous flow, helping to distinguish HCCs from
metastases or haemangiomas, which demonstrate
little or no flow. All carcinomas demonstrate neovascularization:
the formation of numerous new
blood vessels to supply the growing lesion. The
vascular characteristics of such new vessels are different
from those of the normal, established vessels.
The lesion usually demonstrates a knot of
short, tortuous vessels with an irregular course.
Because these new vessels have a paucity of
smooth muscle in the intima and media, they
exhibit a low resistance to blood flow, having relatively
high end diastolic flow (EDF). They are
able to multiply relatively quickly, causing arteriovenous
shunting within the mass which may result
in high velocities.
A
B
C
D
Figure 4.18 (A) Exophytic hepatocellular carcinoma (HCC) in a patient with cirrhosis. (B) Multifocal HCCs (arrows) in a
cirrhotic patient. (C) A patient with chronic Budd–Chiari syndrome has a nodular liver with suspicion of a lesion near the
anterior surface. (D) Administration of contrast in the same patient as (C) demonstrates increased uptake in the arterial
phase, with wash-out of contrast in the late portal phase, helping to locate the lesion, and characterize it as an HCC.