Biology Reference
In-Depth Information
18.1
Introduction
Nodular parenchymal hepatic lesions are frequent in small animals. Focal nodular
hyperplasia is present in 70% of dogs older than 6 years (Bergman
1985
). Other less
common lesions are represented by hematoma, cyst, abscess, focal necrotic area,
primary neoplasm (hepatocellular carcinoma, biliary carcinoma, carcinoids, sar-
coma), or secondary neoplasm (hemangiosarcoma, insulinoma, pancreatic carci-
noma, fibrosarcoma) (Haers and Saunders
2009
). Ultrasonography (US) with
second-generation contrast medium, a quite recent diagnostic method, frequently
used in human and veterinary medicine, allows the visualization of lesion perfusion
in real time. The ultrasonographic features of normal liver vascularity have been
described (Ziegler et al.
2003
), and three vascular phases have been identified:
arterial phase, portal phase, and late phase (Ziegler et al.
2003
; O'Brien et al.
2004
).
The arterial phase is identified 7-10 s after the intravenous injection of the contrast
medium and persists for approximately 15 s. Afterward, portal phase is identified
after 35-40 s and continues for approximately 120 s. The late phase is determined
by the presence of the contrast medium within the hepatic sinusoid and can persist
for 4-20 min, depending on the contrast medium employed. The pathological
modifications of hepatic vascularity during the three mentioned vascular phases
are important for the characterization of hepatic lesions. Malignant lesions can be
differentiated from benign lesions because the former have an early arterial phase
and poor to absent portal and late phases compared to normal liver parenchyma
(Ziegler et al.
2003
; O'Brien et al.
2004
; Quaia
2007
). The hypoechogenicity of
nodular hepatic lesions at peak liver enhancement and during the portal/late phases
has been significantly associated with malignancy, with high positive and negative
predictive values in both human and veterinary medicine (O'Brien et al.
2004
;
Quaia
2007
). The aim of this study was to report our experience with the character-
ization of benign and malignant nodular hepatic lesions in the dog and cat with
contrast-enhanced US and to compare our data with those published in the
literature.
18.2 Materials and Methods
Thirteen dogs of different breeds and sexes, from 5 to 13 years old, and two cats
(mixed breeds, a male and a female, 7 and 10 years old respectively), with single or
multiple nodular hepatic lesions were considered. Each animal underwent abdomi-
nal US, anesthesia, contrast US of the nodular hepatic lesions, ultrasound-guided
fine needle aspirate/biopsy or surgical removal of the hepatic lesions, and cytologi-
cal/histological examination of the collected specimen. Contrast-enhanced US
(CEUS) has been performed using two different ultrasonographic units and the
CnTI harmonic technique (Esaote
®
Megas GPX and Esaote
®
MyLab 30 GOLD).
Two different probes were employed: a convex probe with a receiving frequency of
