Transcript Septic Arthritis: Workup

Septic Arthritis: Workup
Laboratory Studies
• Complete blood count with differential - Often reveals leukocytosis
with a left shift
• Erythrocyte sedimentation rate and C-reactive protein - Helpful in
monitoring treatment course
• Blood cultures
– May be positive in up to 50% of S aureus infections
– Very poor in detecting N gonorrhoeae (Approximately 10% of cases
prove positive.)
• Urethral, cervical, pharyngeal, and rectal cultures - Much higher
yield for N gonorrhoeae than in blood cultures
• Synovial fluid analysis – Gram stain, culture, cell counts, and crystal
analysis Synovial Fluid Classification (Modified from Schumacher
HR. Pathologic Findings in Rheumatoid Arthritis)
Quality
Reference Range Noninflammator Inflammatory
y
Septic
Volume, mL
3.5<
3.5>
3.5>
3.5>
Viscosity
High
High
Low
Variable
Color
Clear
Straw-yellow
Yellow
Variable
Clarity
Transparent
Transparent
Translucent
Opaque
WBC, µL
200<
2,000-200
75,000-2,000
Often >100,000
PMN, %
%25<
%25<
%50>
%75>
Culture result
Negative
Negative
Negative
Often positive
Mucin clot
Firm
Firm
Friable
Friable
Glucose
~Blood
~Blood
Decreased
Very decreased
Imaging Studies
• Plain radiography - Anteroposterior
and lateral views
• Findings are often normal.
• Radiography may be helpful when considering hip
involvement in young children.
• Look for soft-tissue swelling around the joint,
widening of the joint space, and displacement of
tissue planes.
• In later stages of progression, look for bony
erosions and joint space narrowing.
• Ultrasonography
• This study is very sensitive in detecting joint
effusions generated by septic arthritis.
• Ultrasound can be used to define the extent of
septic arthritis and help guide treatment.
• Ultrasound helps to differentiate septic
arthritis from other conditions (eg, soft-tissue
abscesses, tenosynovitis) in which treatment
may differ.
• Nuclear scanning:
• This study may be helpful to differentiate
transient synovitis from septic arthritis.
• Anteroposterior view of the knee demonstrates patchy
demineralization of the tibia and femur and joint-space
narrowing caused by tuberculoid infection of the joint
• Hyperintense joint effusion and increased signal
intensity in the bone marrow of the pubic rami shown
in septic arthritis with associated osteomyelitis and
inflammatory changes in the soft tissues.
• Anteroposterior view of the shoulder
demonstrates subchondral erosions and
sclerosis in the humeral head.
• Septic arthritis with associated soft tissue abscess. Coronal T2weighted fat-saturated MRI of the shoulder demonstrates a joint
effusion, bone marrow edema, and marked adjacent soft tissue
inflammation with a fluid collection in the infraspinatus muscle.
Diagnostic Procedures
• Needle aspiration
• May be the initial best diagnostic and therapeutic
procedure in the vast majority of cases
• May allow thorough decompression of joint
• Can be repeated serially to achieve relief of
symptoms, decrease joint effusion, and clear
bacteria and synovial WBCs.
• Poor choice in joints with loculations