Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

Chapter Three The Abd omen 285
Unless present in massive amounts, fluid within the peritoneal cavity facilitates the ultrasonographic
examination (Fig. 3-35). 49,151 If marked distention of the abdomen has
occurred, removal of the fluid is recommended, because the patient will be more comfortable
and will breathe less rapidly and the abdominal wall will be more compressible, allowing the
placement of the transducer closer to the structure of interest. In an experimental study in
dogs, ultrasonography was more sensitive than radiography in detecting abdominal fluid. As
little as 2 ml of fluid per pound of body weight could be detected using ultrasonography,
while at least 4 ml of fluid per pound of body weight were required before the fluid could be
detected radiographically. 152,153 The nature of the abdominal fluid cannot be determined
using ultrasonography. If the fluid contains a large number of cells, these can be recognized
as floating grainy objects, and fibrin strands also can be identified. In most instances, the
ultrasonographic examination provides guidance for abdominocentesis. Peritoneal masses or
granulomas can be detected using ultrasonography. 154,155 These may be observed as heteroechoic
structures on the parietal peritoneum attached to the body wall or may be seen on the
serosal surface of abdominal viscera. Abdominal abscesses may produce an irregularly
defined hypoechoic mass with little or no through transmission. A definitive diagnosis based
solely on the ultrasonographic examination is rarely possible. 156
Ultrasonographic examination of calcified abdominal masses is often unrewarding. The
mineral produces shadowing, which obscures the internal structure of the mass (Fig. 3-36).
However, information can be gathered about the unaffected, adjacent parenchyma, which may
be helpful in explaining the cause or understanding the significance of the calcified lesions.
A
B
Fig. 3-35 Sonograms of the abdomen
of a 14-year-old castrated male cat
with a history of abdominal distention
and a palpable abdominal mass. There
is anechoic free peritoneal fluid
throughout the abdomen. This can be
seen outlining the spleen and gallbladder
(A), the folds of the mesentery and
omentum (B), several intestinal loops
(C to F), and the urinary bladder wall
(D to F). Diagnosis: Ascites, lymphoma.
C
D
E
F