Imaging in Gout and Other Crystal-Related Arthropathies

In this article, the authors consider the manifestations of intraarticular and periarticular crystal deposits. Most cases of crystal deposits are asymptomatic and represent incidental findings at imaging. In symptomatic arthropathies, imaging can play an important role in the diagnosis and assessment of disease progression and the extent of crystal deposits. Conventional radiography is the most common imaging modality. But ultrasound, conventional computerized tomography (CT), dual-energy CT, and MRI play an increasing role. The authors review typical radiographic features of crystal-induced arthropathies and findings that help to differentiate them. The authors also emphasize the increasing role of complementary imaging techniques.

Key points

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Crystal deposits in and around the joints are common and most often encountered as incidental imaging findings in asymptomatic patients.
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In the chronic setting, imaging features of crystal arthropathies are usually characteristic and allow the differentiation of the type of crystal arthropathy, whereas in the acute phase and in early stages, imaging signs are often nonspecific, and the final diagnosis still relies on the analysis of synovial fluid.
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Radiography remains the primary imaging tool in the workup of these conditions; ultrasound has been playing an increasing role for superficially located crystal-induced arthropathies, and computerized tomography (CT) is a nice complement to radiography for deeper sites.
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When performed in the acute stage, MRI may show severe inflammatory changes that could be misleading; correlation to radiographs or CT should help to distinguish crystal arthropathies from infectious or tumoral conditions.
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Dual-energy CT is a promising tool for the characterization of crystal arthropathies, particularly gout as it permits a quantitative assessment of deposits, and may help in the follow-up of patients.

Introduction

The deposition of microcrystals within and around the joint is a common phenomenon. Intra-articular microcrystals are the most frequent cause of joint inflammation in adults. The most common types are monosodium urate (MSU), the cause of gouty arthropathy; calcium pyrophosphate dihydrate (CPP), causing CPP deposition disease (CPPD); and basic calcium phosphate (BCP), causing BCP deposition disease ( Table 1 ). In this article, the authors consider the manifestations of intra-articular as well as periarticular crystal deposits. Most cases of crystal deposits are asymptomatic and represent incidental findings at imaging. In case of symptomatic arthropathies, imaging can play an important role in the diagnosis and the assessment of disease progression as well as the extent of crystal deposits. Conventional radiography is the most common imaging modality and still remains essential to the workup. But ultrasound (US), conventional computerized tomography (CT), dual-energy CT (DECT), and MRI all play an increasing role. For example, the new 2015 American College of Rheumatology/European League Against Rheumatism’s classification criteria for gout take into account the radiological signs obtained by standard radiology as well as by DECT and US.

Table 1

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