Page 1443 - Small Animal Internal Medicine, 6th Edition

CHAPTER 88 Lymphadenopathy and Splenomegaly 1415

seen in inflammatory, infectious, or neoplastic disorders; ventrodorsal or dorsoventral projections. In some breeds,
hemolytic anemia is usually present in patients with hemo- such as Greyhounds, the spleen appears to be large on plain
VetBooks.ir parasitic lymphadenopathies or splenomegaly and in some radiographs and ultrasonograms. On plain radiographs,
large splenic masses usually appear in the caudal abdomen
dogs with malignant histiocytosis or hemophagocytic syn-
drome. Severe nonregenerative anemia may be seen in dogs
results in a diffuse congestive splenomegaly, making radio-
with chronic ehrlichiosis, in cats with feline leukemia virus– or the midabdomen. Tranquilization or anesthesia usually
related disorders or feline immunodeficiency virus–related graphic interpretation of splenic size extremely difficult. CT
disorders, and in dogs and cats with primary bone marrow is a useful diagnostic tool for dogs with focal or diffuse
neoplasms (e.g., leukemias, multiple myeloma). splenomegaly.
Thrombocytopenia is a common finding in patients with Ultrasonography is the noninvasive procedure of choice
ehrlichiosis, RMSF, anaplasmosis, sepsis, lymphomas, leuke- to evaluate intraabdominal lymphadenopathy and spleno-
mias, multiple myeloma, systemic mastocytosis, and some megaly because it can accurately depict the size of enlarged
immune-mediated disorders. Pancytopenia is common in lymph nodes and the spleen (Figs. 88.5 and 88.6) so that the
dogs with chronic ehrlichiosis or systemic immune-mediated patient’s response to therapy can be monitored. In addition,
disorders, in dogs and cats with lymphoma or leukemia, and ultrasound-guided FNA or biopsies can be performed with
in cats with disorders associated with retroviral infections. minimal complications. Abdominal ultrasonography can
Two major serum biochemical abnormalities are of diag- reveal diffuse splenomegaly, splenic masses, splenic conges-
nostic value in dogs and cats with lymphadenopathy or tion, hepatic nodules, or other changes; in addition, color
diffuse splenomegaly: hypercalcemia and hyperglobulin- flow Doppler allows for the evaluation of splenic blood flow
emia. Hypercalcemia is a paraneoplastic syndrome that (Huynh and Berry, 2017). A major issue a clinician fre-
occurs in approximately 10% to 20% of dogs with lymphoma quently must deal with is the incidental splenic nodule in an
and multiple myeloma, although it may also occur in dogs older dog; these lesions are common and usually clinically
with blastomycosis or other chronic inflammatory disorders. irrelevant but tend to cloud the clinical picture in a patient
It is extremely rare in cats with these diseases. Monoclonal with intraabdominal neoplasia. If possible, splenic nodules
hyperglobulinemia commonly occurs in dogs and cats with should be aspirated and evaluated cytologically; occasionally,
multiple myeloma and occasionally in dogs with lymphoma, immunophenotyping or PARR are needed to distinguish
ehrlichiosis, or leishmaniasis (see Chapter 89). Polyclonal between lymphoma and regenerative nodules. Of note,
hyperglobulinemia commonly occurs in dogs and cats with however, is that the presence of hepatic nodules in a dog with
systemic mycoses, in cats with feline infectious peritonitis, a splenic mass does not constitute a valid reason for an
and in dogs with ehrlichiosis, anaplasmosis, or leishmaniasis owner to decline treatment or request euthanasia because
(see Chapter 89). regenerative liver nodules are indistinguishable from meta-
Serologic and microbiologic studies should always be static lesions. Moreover, hypoechoic splenic nodules are fre-
conducted in dogs and cats with suspected infectious quently found in normal dogs. Computerized tomography
lymphadenopathy-splenomegaly. Serologic tests or PCR cannot readily distinguish between benign and malignant
assay for canine ehrlichiosis, RMSF, brucellosis, and systemic masses in dogs (Jones et al., 2016).
mycoses may help diagnose regional or systemic lymphade-
nopathies. Lymph node specimens for bacterial and fungal
cultures should also be obtained if necessary.
Imaging
Radiographic abnormalities in dogs with lymphadenopathy
can be related to the primary disorder or can reflect the loca-
tion and degree of lymphadenopathy. In general, plain radio-
graphs or computed tomography (CT) scans are helpful in
dogs and cats with solitary lymphadenopathy to search for
primary bone inflammation or neoplasia, in those with gen-
eralized peripheral (superficial) lymphadenopathy to detect
intrathoracic or intraabdominal lymph node enlargement
(see Fig. 79.7), and in those with deep regional lymph-
adenopathy involving the thoracic cavity to determine the
distribution and size of the affected nodes and changes in the
pulmonary parenchyma and pleural space.
The spleen is normally well visualized on plain abdominal FIG 88.5
radiographs, but its appearance can vary widely. On dorso- Ultrasonographic appearance of a complex rapidly growing
splenic mass in a 12-year-old female spayed Greyhound.
ventral or ventrodorsal views, the spleen is seen between Note the lack of blood flow on color flow Doppler.
the gastric fundus and left kidney. The size and location of Splenectomy revealed a hyperplastic lymphoid nodule with
the spleen are more variable on lateral radiographs than on hematoma formation.