eMedicine Specialties > Emergency Medicine > Rheumatology
Gout and Pseudogout: Differential Diagnoses & Workup
Updated: Aug 27, 2009
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
Differential Diagnoses
Other Problems to Be Considered
Acute sarcoidosis (rare)
Amyloidosis
Calcific periarthritis
Infectious or septic arthritis
Multicentric reticulohistiocytosis
Psoriatic arthropathy
Spondyloarthropathy
Trauma
Type IIa hyperproteinemia
Workup
Laboratory Studies
- Diagnostic arthrocentesis is indicated for every patient in whom a diagnosis has never been proven by joint aspiration and for those in whom a possibility of septic arthritis exists. A prior history of gout or pseudogout does not rule out the possibility of acute septic arthritis. In fact, the latter is more common in patients with a history of crystal-induced arthritis. Septic arthritis must be diagnosed and treated promptly. Irreversible damage can occur within 4-6 hours, and the joint can be completely destroyed within 24-48 hours.
- Joint fluid analysis
- Send joint fluid for fluid analysis, including cell count and differential, Gram stain, culture and sensitivity, and microscopic analysis for crystals. If crystals are seen, their shape and appearance under polarized light can aid in diagnosis.
- In gout, crystals of MSU appear as needle-shaped intracellular and extracellular crystals. When examined with a polarizing filter, they are yellow when aligned parallel to the axis of the red compensator, but they turn blue when aligned across the direction of polarization (ie, they exhibit negative birefringence).
- In pseudogout, CPP crystals appear shorter and often rhomboidal. Under a polarizing filter, CPP crystals do not change color depending upon their alignment relative to the direction of the red compensator.
- In crystal arthritis, the WBC count in the joint fluid is usually 50,000-100,000.
- Even in the presence of crystals in the joint fluid, blood cultures are indicated if any sign of systemic toxicity is present. Septic arthritis can occur in patients with active crystalline arthropathy.
- Gouty attacks are triggered by crystal formation in synovial fluid. They are not related to serum levels of uric acid. Thus, a normal serum uric acid level does not exclude the diagnosis of acute gout, and an elevated level does not prove the diagnosis.
- Pseudogout attacks can be triggered by many metabolic abnormalities. Thus, patients who have an initial attack of arthritis with CPP crystals should have a workup including a chemistry screen; magnesium, calcium, and iron levels; and thyroid function tests.
- WBC count usually is elevated.
- Erythrocyte sedimentation rate (ESR) usually is elevated during acute attacks.
- Hyperuricemia may be present but is not diagnostic. Renal uric acid excretion should be obtained in high-risk patients, including those with renal calculi, strong family history of gout, and first attack before age 25 years.
Imaging Studies
- Radiographs
- Plain radiographs of the affected joint or joints are indicated.
- Radiographic lesions of chronic gout may appear as rat-bitten, sclerotic regions on the joint surfaces, with overhanging margins.
- Patients with new onset of acute gout usually have no radiographic findings.
- Patients with pseudogout usually have degenerative joint changes and may have calcifications in the soft tissues, tendons, or bursae.
- Bone scan reveals increased nuclide concentration at affected sites.
- MRI
- MRI is capable of detecting crystal deposits but is not part of any routine evaluation for acute arthritis.
- MRI can be very useful in determining the extent of the disease and may help in the differential diagnosis.
- MRI with gadolinium is recommended to evaluate any tendon sheath involvement and when osteomyelitis in the differential diagnosis.
- Large deposits of crystals may be seen in bursae or ligaments. Tophi usually are low or intermediate signal intensity on T1-weighted images.
- Ultrasonography
- Initially anechoic at first gouty attack, then diffuse enhancement at superficial cartilage margins.6
- Chondrocalcinosis show up as a thin, hyperechoic band parallel to hyaline cartilage and punctuated pattern on fibrocartilage.
Procedures
- Aspiration and biopsy
- Joint aspiration is the principal procedure used to make the diagnosis of crystal-induced arthritis and to rule out septic joint effusion.
- Biopsy of synovial membrane or subcutaneous nodule includes an examination with polarizing optics.
More on Gout and Pseudogout |
| Overview: Gout and Pseudogout |
 Differential Diagnoses & Workup: Gout and Pseudogout |
| Treatment & Medication: Gout and Pseudogout |
| Follow-up: Gout and Pseudogout |
| References |
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References
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Further Reading
Keywords
calcium pyrophosphate disease, CPPD, peripheral arthritis, sodium urate crystals, monosodium urate monohydrate crystals, MSU crystals, calcium pyrophosphate crystals, CPP crystals, podagra, hyperuricemia, primary gout, secondary gout, intermediate gout, late-phase gout, pseudogout, tophi, gouty nephropathy, gouty arthritis, first metatarsophalangeal joint pain, uric acid, increased serum uric acid, arthritis nodosa, arthritis uratica, foot pain, edema of the foot, crystal-induced arthritis, joint edema, acute arthritis, lysis of polymorphonuclear white blood cells, inflammatory crystalline arthritis, acute septic arthritis, pseudogout arthritis, carpal tunnel syndrome, arthrocentesis
