Page 1444 - Small Animal Internal Medicine, 6th Edition

1416 PART XIII Hematology

because the diagnosis is usually that of lymphoma, with the
7 presence of well-differentiated or poorly differentiated lym-
VetBooks.ir phoid cells. In those cases, the combination of hematologic
and bone marrow findings is usually diagnostic. Bone
marrow evaluation should always be done before splenec-
tomy in patients with cytopenias because the spleen may
7 assume the primary hematopoietic function in dogs and cats
cm/s
with primary bone marrow disorders, such as hypoplasia or
aplasia. Splenectomy in these animals could remove the sole
source of circulating blood cells, leading to death.
Cytologic evaluation of lymph node and splenic aspirates
provides the clinician with a wealth of information and often
constitutes the definitive diagnostic procedure in animals
A with lymphadenopathy or diffuse splenomegaly. In my expe-
rience, cytologic evaluation of appropriately collected speci-
mens yields diagnostic findings in approximately 80% to
90% of dogs and 70% to 75% of cats with lymphadenopathy
and in approximately 80% of dogs and cats with diffuse
splenomegaly.
Although superficial lymph nodes can be aspirated with
minimal difficulty, the successful aspiration of intrathoracic
or intraabdominal lymph nodes or spleen requires some
expertise and occasionally must be done under the guidance
of imaging techniques (e.g., ultrasonography, CT; see Chapter
74). To perform FNA of a superficial node, the area does not
have to be surgically prepared. However, the aspiration of
intrathoracic and intraabdominal structures (e.g., spleen)
requires surgical preparation of the area and adequate
restraint of the animal. Certain intraabdominal lymph nodes
(e.g., markedly enlarged mesenteric or iliac nodes) are easily
aspirated transabdominally by using manual isolation of the
mass. Splenic aspirates are obtained with the animal in right
lateral or dorsal recumbency, with manual restraint or mild
B sedation. Transabdominal splenic FNA in dogs or cats chem-
ically restrained with phenothiazine tranquilizers or barbi-
FIG 88.6 turates usually yields blood-diluted specimens as a result of
(A) Ultrasonographic appearance of a splenic torsion in a splenic congestion; the same occurs when a syringe is
Chow Chow. Note the hypoechoic echotexture and lack of attached to the needle and suction is applied (LeBlanc et al.,
blood flow on color Doppler. (B) Surgical procedure in the 2009).
same dog. Notice the markedly enlarged, deep purple
torsed spleen. (A courtesy Dr. Pablo Gómez Ochoa, Splenic biopsies for histopathology can also be obtained
Vetoclok, Zaragoza, Spain.) percutaneously using ultrasonographic guidance and a
Tru-Cut–style needle. In a recent study, percutaneous FNA
samples were compared with needle core biopsies (NCBs).
Radionuclide imaging of the spleen (and, less commonly, Forty-one dogs with splenic lesions were studied prospec-
of lymph nodes) using technetium-99m–labeled sulfur tively (Watson et al., 2010). Safety was assessed in 38 dogs,
colloid has become an accepted method of splenic imaging and no complications were encountered. Clinical and ana-
in humans and small animals. However, this technique only tomic pathologists reviewed each FNA and NCB sample,
evaluates the spleen’s ability to clear particulate matter and respectively, without knowledge of the other’s results. Diag-
rarely provides a morphologic diagnosis. noses were categorized as neoplastic, benign, inflammatory,
normal, or nondiagnostic. The level of agreement between
Additional Diagnostic Tests sampling methods was categorized as complete, partial, dis-
Evaluation of bone marrow aspirates or core biopsy speci- agreement, or not available. Test correlation was performed
mens may be beneficial in dogs and cats with generalized in 40 dogs. Nondiagnostic results occurred in 5 of 40 NCB
lymphadenopathy or splenomegaly caused by hemolym- (12.5%) and no FNA samples. Neoplasia was diagnosed in
phatic neoplasia or systemic infectious diseases. For example, 17 of 40 dogs (42.5%), benign changes in 20 of 40 dogs
acute or chronic leukemia in dogs may be difficult to diag- (50%), inflammatory disorders in 0 of 40 dogs, and normal
nose on the basis of lymph node cytologic findings alone in 2 of 40 dogs (5%). One of the 40 dogs (2.5%) had a