Table of contents
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Synovial Fluid Analysis
- Consists of plasma (ultrafiltrate) + hyaluronic acid that lubricates joint
- Absolute Indication!:
- Acute inflammatory monoarthritis that is not traumatic!!
- Contraindications:
- Absolute:
- Open lesion
- Suspected infection of overlying skin
- Relative
- Bleeding diathesis
- Thrombocytopenia
- Prosthetic joint
- Absolute:
- Synovial Fluid Examination:
- Cell count & Differential (bacteria, fungi, Lyme)
- Culture & Gram Stain
- Crystals (Microscopy with polarized light)
- Gout (Monosodium Urate) -->
- Needle-shaped
- Negatively birefringent (yellow parallel to polarization, blue when perpendicular)
- During acute attack see them being phagocytosed in macrophages (intracellular)
- Pseudogout (Calcium pyrophosphate dihydrate) --> r
- Rhomboid-shaped
- Positively birefringent (very weak birefringent, not as bright/pretty, and blue when parallel to polarizer)
- Gout (Monosodium Urate) -->
- NOTE: Seeing crystals on joint fluid aspiration does not rule out infection --> must cover with antibiotics (i.e. Vanco+ceftriaxone) and await culture!
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Gout Pseudogout
- General Principle:
- Synovial leukocyte count:
- < 2,000 -- Non-inflammatory
- 2,000 - 50,000 - Likely inflammatory, can be infectious as well (does not rule out infection!!)
- > 50,000 - Very likely infectious
- PMNs
- < 25% -- Non-inflammatory
- >50% -- Inflammatory
- > 75% -- Likely infectious.
- Synovial leukocyte count:
-
Parameter Normal Non-Inflammatory Infammatory Infectious Hemorrhagic Colour Pale Yellow Pale Yellow Pale Yellow Yellow-White Red/Browth Clarity Clear Clear Opaque Opaque Sanguinous Viscocity High High Low Low Variable WBC/mm3 <200 <2,000 >2,000 >50,000 Variable %PMN <25% <25% >25% >50% Variable Culture/Gram POSITIVE Examples Trauma
Osteoarthritis
Seropositives
Seronegatives
Crystal
Arthropathies
S. aureus
Gram neg.
Gonococcal
(hard to cult)
Trauma
Hemophilia
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