Age / Sex : 40 / M

Chief complaint: Right knee swelling & pain (Spontaneous, 3months)

What is your impression?

Two weeks later, you can see the final diagnosis with a brief discussion of this case.

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Courtesy: Seon Kwan Juhng, Wonkwang university hospital

Gouty arthritis

Discussion

Findings:

Plain radiograph – Bulging contoured opacity at the lateral aspect to the lateral femoral condyle of knee joint

MR – Intra- and peri- articular discrete multifocal low signal intensity lesions on all pulse sequences

Differential Diagnosis: RA, Chronic tuberculous arthritis, Hemophilic arthropathy, Diffuse-type giant cell tumor(previously known as PVNS)

Diagnosis: Gouty arthritis

Discussion:

Gouty arthritis is a metabolic disease characterized by an increase in serum urate concentration, episodes of acute arthritis, deposits of monosodium urate monohydrate crystals (tophi) within or around the joints. Articular manifestations occur in the different stages of the disease and include acute arthritis, an intermediate phase, and chronic tophaceous gout. The diagnosis of acute monoarticular gouty arthritis is usually established with clinical and laboratory assessment. However, monoarticular or polyarticular forms of chronic tophaceous gout may present diagnostic difficulties, for which imaging evaluation is necessary. Histologically, a tophus consists of central cryslline core surrounded by coronal zone and a peripheral fibrovascular zone.

  The tophi appear as eccentric or asymmetric soft-tissue masses around the joint. Most tophi are deposited in the periarticular soft tissue, although they may also be intraosseous, intraarticular, or extraarticular. On MR imaging, tophi showed homogeneous low signal intensity lesions, similar to that of muscle on T1WI, and various signal lesions d/t urate or calcium composition on T2WI. Significant gadolinium enhancement of tophus can be shown owing to its outer fibrovascular zone and hypervascular granulation tissue surrounding the tophus. Dual-energy CT imaging easily allows the separation and characterization of calcium, a high-molecular-weight compound, from uric acid, a low-molecular-weight compound, making DECT an important noninvasive tool in diagnosing gout.

References:

Gout & Other Crystal Arthropathies, AJR:168, February 1997

Imaging of Intraarticular Masses RadioGraphics 2005;25:105-119

Nonseptic Monoarthritis: Imaging Features with Clinical and Histopathologic Correlation Radiographics. 2000;20:S263-S278

Dual-Energy CT: A Promising New Technique for Assessment of the Musculoskeletal System AJR 2012;199: S78-S86