MRI of gout: a pictorial review

Gout is a systemic, inf lammatory arthritis caused by deposition of monosodium urate (MSU) crystals within synovial or periarticular tissue. Currently, it is estimated to affect 6.1 million Americans [1,2]. The acute phase of gout manifests clinically as a monoarticular inflammatory arthritis, and can mimic a septic joint. Chronic gout is characterized by the formation of tophi, both intraosseous and periarticular. If left untreated, chronic tophaceous gout will lead to destructive arthropathy as well as other morbidities. The classic radiographic findings in gout are well-defined, ‘punched-out’ periarticular erosions with overhanging edges, with relative preservation of joint space and osseous mineralization and have been well described in the literature [3]. However, these findings usually manifest late in the disease [4]. Radiographs are often utilized in the initial diagnosis to exclude other causes of joint pain. The evaluation of gout remains primarily a clinical and laboratory diagnosis. The gold standard in the diagnosis of gout is aspiration of the joint, with detection of negatively birefringent MSU crystals under polarizing microscopy [5,6]. However, this is not routinely performed in clinical practice [7]. This article will provide a pictorial review of the various magnetic resonance (MR) appearances of tophaceous gout. The findings on MR of gouty arthropathy include synovitis or synovial pannus, tophi, erosions and reactive bone marrow change. MR has been shown to be much more sensitive than conventional radiographs in the detection of erosions [8]. MR also provides excellent soft tissue contrast to detect complications of MSU deposition, such as bursitis, intra-articular tophi, tenosynovits and tendon ruptures [9–11]. MR characteristics of gouty tophus have been described as near isointense to skeletal muscle on T 1 -weighted sequences, and heterogeneous in signal on T 2 -weighted sequences [12]. Additionally, gouty tophus do not have a characteristic pattern of enhancement [13]. Most of the articles in the literature have focused on the appearance of chronic, tophaceous gout. However, in addition, initial acute gout flares have been shown to demonstrate synovitis, reactive bone marrow edema and erosions [14]. Unfortunately, the imaging characteristics of tophi, as well as other MR findings in gout lack specificity. Other inflammatory arthritides, as well as infectious arthritis can have a similar appearance and remain diagnostic considerations based solely on the MR appearance. Specifically, gouty tophi are grouped in the MR differential diagnosis of intra-articular masses, of which the most common include the synovial pannus of rheumatoid arthritis, amyloid arthropathy and chronic granulomatous infections, such as tuberculosis [15]. Occasionally, if the tophi are heavily calcified, they can also simulate pigmented villonodular synovitis on MR as the calcification demonstrates similar signal as hemosiderin [16]. In the following pictorial review, Figures 1–5 review the MR appearance of tophaceous gout, as well as demonstrate some of the associated soft tissue complications, beginning in the peripheral appendicular skeleton, and advancing proximally. Accompanying radiographs also demonstrate the marked, increased sensitivity of There has been renewed clinical interest in gout secondary to the recent advances in the understanding of its cellular inflammatory mediators, which have led to new and emerging therapies for treatment. The role of advanced imaging in gout is currently evolving to compliment modern clinical challenges in the treatment of gout. Furthermore, the clinical diagnosis of gout remains potentially challenging, especially in the setting of an atypical presentation and advanced imaging is often utilized in these circumstances. This article seeks to provide a timely review of the magnetic resonance features of chronic tophaceous gout in a pictorial exhibition, as well as provide a future perspective of the utilization of advanced imaging: computed tomography, MRI and ultrasound in the clinical management of gout.