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Musculoskeletal Imaging

E2389. Gout: A Multimodality Imaging Review With Attention to Recent Developments in Imaging Diagnosis

Sever A,  Rheinboldt M. Henry Ford Hospital, Detroit, MI

Address correspondence to M. Rheinboldt (mrheinbold@yahoo.com)

Background Information: Gout is a metabolic disorder secondary to an increase in production or diminished excretion of uric acid, leading to hyperuricemia and precipitation within the joints and soft tissues. Approximately 2% of the industrialized world is affected with rising demographics attributed to increasing obesity, hypertension, poor dietary habits and alcohol consumption. Early diagnosis and treatment are paramount to decrease musculoskeletal disability as well as to diminish associated increased risk for myocardial infarction, stroke, metabolic syndrome and type II diabetes Establishing a diagnosis is based on a composite of laboratory and clinical findings as well as imaging studies. Though joint aspiration of monosodium urate crystals is the reference standard, diagnosis is usually presumptive and noninvasive. Radiography, ultrasound, MDCT, and dual-energy CT (DECT) and MRI all play contributory roles, with DECT and ultrasound emerging in the forefront for early detection.

Educational Goals/Teaching Points: Our aim is to review the demographic, clinical, and laboratory features of urate-related arthropathy; to illustrate classic radiographic, sonographic, CT, and MRI findings of acute and chronic gout arthropathy, tenosynovial and soft tissue tophaceous involvement; to discuss and illustrate the growing role of both DECT and ultrasound in the emergency setting; and to illustrate differential diagnostic imaging considerations.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: Sonography is increasingly being used in both the diagnosis and surveillance of gout arthropathy. In addition to generic signs of joint inflammation including synovial hypertrophy and hyperemia, erosions and effusion, more specific features have been identified, including detection of echogenic crystal aggregates and the double contour sign. Using the difference in absorption spectra between urate crystals and surrounding osseous structures and soft tissues, DECT has been shown to be useful in both the initial diagnosis and surveillance of gout arthropathy, with a sensitivity of up to 84% and a specificity of 93%. Limitations include a minimal deposit size of 2 mm, hence lower sensitivity in the early disease phase, and diminished sensitivity in conjunction with prolonged urate-lowering therapy. MRI has a greater sensitivity for the detection of erosions than ultrasound or radiography. Synovial thickening, enhancement, effusion, erosions, and bone marrow edema are well demonstrated by MRI. In comparison to other inflammatory or infectious mono- or polyarticular arthropathies, marrow edema in the setting of gout is typically mild at most.

Conclusion: Although radiographic manifestations may lag behind the onset of gout arthropathy, newer modality applications including sonography and DECT offer an expanding role in both disease detection and surveillance. Conventional CT and MRI may be of use for work-up of atypical cases and, although imaging features overlap with other arthritides, familiarity with the typical findings of urate-related arthropathy should allow a narrow differential diagnosis and help expedite timely and appropriate care.