Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

286 Small Animal Radiolo g y and Ultrasono graphy
Fig. 3-36 Longitudinal sonograms
of the midabdomen of a 14-year-old
castrated male cat with a history of
anorexia and weight loss of 4 months
duration. The cat was seropositive
for feline leukemia virus (FeLV).
There is a heteroechoic mass identified
in the midabdomen. This mass
contains many hyperechoic foci of
varying sizes. The mass was not
associated with the GI tract. This is
indicative of a mesenteric mass with
mineral foci within the mass.
Diagnosis: Lymphoma.
Air within the peritoneal cavity may be detected during the ultrasonographic examination.
It is hyperechoic and results in reverberation, comet-tail, and ring-down artifacts
(Fig. 3-37). Important features that identify the presence of free air are its location away
from the intestines and its movement with changes in the animal’s position. It is our opinion
that peritoneal and retroperitoneal air are best assessed radiographically.
Masses may be identified in the abdomen. They usually are related to an organ of origin,
based upon their location and their effects upon other regional organs. 157 Masses that
may not be clearly identifiable as to origin include lymphadenopathy, tumors of nonspecific
origin (e.g., serosal or vascular origins), ectopic pregnancy, foreign bodies, granulomas,
or abscesses. 154,158-175
Retroperitoneal Space. The retroperitoneum may be affected by the presence of air, fluid, or
masses. The differential diagnosis for retroperitoneal fluid includes hemorrhage (this seems
to be a preferential site for hemorrhage in some cases of warfarin toxicity), pus, urine from
ruptures of the kidney or ureters, and edema fluid. 176-179 Pneumoretroperitoneum may
result from dissection of air from a pneumomediastinum, infection with a gas-forming
organism, or a penetrating wound. Retroperitoneal masses are uncommon and may arise
from organs in the area, metastatic spread from other sites, or miscellaneous structures,
including carcinoid tumors.
L I V E R A N D G A L L B L A D D E R
Radiographic Abnormalities
Density Changes. Radiographic lesions of the liver are frequently nonspecific, but they
will support diagnoses indicated by other data. Density changes in the liver are uncommon,
although calcifications and gas accumulations have been described. 180-187 The liver may be
partly or almost completely calcified in end-stage liver disease, and with abscess, tumor,
hematoma, or cyst (Figs. 3-38 and 3-39). Although the most common pattern of calcification
is punctate or stippled, the calcification also may appear as larger aggregations or an
“eggshell” pattern. Choleliths, or gallstones, usually are composed of bile pigments and