Case #2 Answers:
Answer 1
The differential diagnosis includes bacterial and some fungal infections,
crystal diseases such as gout or pseudogout, hemorrhage and trauma. Lyme disease
and Reiter’s syndrome could present this way, but would be accompanied by other
features.
Answer 2
Aspiration of the joint with analysis of synovial fluid is the only essential
test. If uric acid crystals are found, further testing is only needed to assess
therapy (e.g., renal function, K for NSAID use). If crystals are not found
infection becomes the likely culprit. In addition to gramstain and culture of
the synovial fluid, blood cultures and culture of any potential source of
infection are indicated. X-ray is not likely to yield a diagnosis, but is useful
as a baseline if infection is suspected.
Answer 3
Crystal analysis, gram stain and culture and WBC are the
key information obtained from synovial fluid, synovial glucose (< 50% serum) is
low in bacterial infection and RA. WBC and differential allow classification
into diagnostic categories.
| Normal | Non-Inflammatory (DJD) | Inflammatory (RA, gout) | Septic | |
| WBC | 0-200 | 200-2000 | 2000-50,000 | >50,000 |
| % PMN | 25 | 50 | 75 | >90 |
Answer 4
No further work-up needed. Decide on management. NSAID or
colchicine or intra-articular steroid injection.
Answer 5
In the absence of crystals, bacterial infection is the likely
cause. Synovial gram stain is positive in only 50%. Synovial and blood cultures
should be sent. The patient should be admitted for IV antibiotics. Staph aureus
and strep species are the most likely organisms. Drainage of the joint is an
essential component of treatment.
Consider surgical drainage if you cannot adequately drain by percutaneous route.
Answer 6
Answer 7
Answer 8
Answer 9