Page 1217 - Small Animal Internal Medicine, 6th Edition

CHAPTER 68 Clinical Manifestations of and Diagnostic Tests for Joint Disorders 1189

TABLE 68.1 indicated if there is evidence of multiple organ involvement.
Testing for SLE should include a CBC, platelet count, urine
VetBooks.ir Synovial Fluid Cytology in Common Joint Disorders protein/creatinine ratio, antinuclear antibody (ANA) titer,
and organ-specific tests such as measurement of creatine
WBC/µL
% PMN
kinase for suspected myositis.
Because most dogs with IMPA have nonerosive disease,
Normal 200-3000 <10 radiographs are not always performed during the initial
Degenerative 1000-6000 0-12 diagnostic evaluation. If dogs with presumed IMPA do not
Traumatic Variable <25 respond quickly and completely to treatment, or if joints are
Septic 40,000-280,000 90-99 unstable or deformed on palpation, radiography should be
Immune-mediated disease employed to evaluate for evidence of erosive disease affecting
Nonerosive immune 4000-370,000 15-95 the articular surfaces, focal “punched out” lesions of lysis in
Erosive arthritis 6000-80,000 20-80 subchondral bone, and proliferation and calcification of
(rheumatoid-like) periarticular soft tissues. Erosive polyarthritis is character-
ized by progressive joint inflammation, destruction, and
PMN, Polymorphonuclear neutrophil leukocytes; WBC, white blood deformity and is an uncommon immune-mediated disorder
cells. in dogs. Serologic testing for rheumatoid factor (RF) (see p.
1204) and synovial membrane biopsy (see p. 1194) aid in the
diagnosis of this rare disorder.
TABLE 68.2 Polyarthritis is uncommon in cats. Infectious arthritis
may be caused by bacteria, Mycoplasma spp., calicivirus
Infectious Causes of Polyarthritis in Dogs and Cats infection, fungi, and some tick-borne pathogens (Lemetayer
and Taylor, 2014). Forms of nonerosive immune-mediated
DOG CAT
polyarthritis include idiopathic/primary IMPA, reactive
Direct inoculation with bacteria or Direct inoculation polyarthritis, rheumatoid arthritis, and (rarely) SLE. Two
hematogenous spread; with bacteria or uncommon erosive immune-mediated disorders causing
Staphylococcus, Streptococcus hematogenous joint damage and destruction in cats are periosteal prolifera-
(most common organisms spread; Pasteurella tive polyarthritis and rheumatoid-like polyarthritis.
cultured), others multocida, others
Borrelia burgdorferi
Leishmania DIAGNOSTIC TESTS
Ehrlichia spp., Rocky Mountain MINIMUM DATABASE
spotted fever, Anaplasma spp.
A minimum database (CBC, serum biochemistry profile,
and urinalysis) should be normal in animals with nonin-
flammatory joint disease. In dogs and cats with polyarthritis,
causes of arthritis include a complete blood count (CBC); it is common to identify a leukocytosis, hyperglobulinemia,
urinalysis; culture of urine, blood, and synovial fluid; and and mild hypoalbuminemia. Thrombocytopenia is common
serology for tick-borne diseases. Thoracic radiographs and in polyarthritis caused by tick-borne pathogens. Organ-
fungal serology may also be warranted. Once infectious isms may be identified within red or white blood cells in
causes of polyarthritis have been ruled out, immune- animals with some infectious causes of polyarthritis (Fig.
mediated conditions should be considered. 68.3). Proteinuria and hypoalbuminemia may be present in
Noninfectious IMPA is common in dogs but uncommon dogs with concurrent glomerulonephritis. Cats with poly-
in cats. Immune-mediated polyarthritis can occur as an idio- arthritis should always be tested for feline leukemia virus
pathic syndrome, as a feature of SLE, or secondary to sys- (FeLV) antigen and feline immunodeficiency virus (FIV)
temic antigenic stimulation (reactive polyarthritis). In antibody. Normal clinical pathologic findings do not rule
reactive polyarthritis, articular deposition of immune com- out polyarthritis.
plexes causes synovitis. Reactive polyarthritis has been
reported in association with chronic bacterial or fungal SYNOVIAL FLUID COLLECTION
infections, neoplasia, and administration of drugs or vac- AND ANALYSIS
cines (Sykes, 2006). An extensive diagnostic evaluation is Synovial fluid collection and analysis is the most useful
sometimes required to rule out reactive polyarthritis (e.g., test for establishing a diagnosis in dogs and cats with joint
CBC, thoracic and abdominal radiographs, ophthalmologic disease. It is of greatest value in confirming that a specific
examination, bacterial culture of urine and blood, lymph joint is abnormal and in differentiating inflammatory from
node aspirates, cardiac ultrasonography, abdominal ultra- noninflammatory disease. Synovial fluid collection and
sound). Normal results on all of these tests warrant a diag- analysis may also provide information regarding a specific
nosis of idiopathic IMPA. Diagnostic testing for SLE is diagnosis.