Impact of sonography in gouty arthritis: Comparison with conventional radiography, clinical examination, and laboratory findings
Introduction
Gout is a common metabolic disorder with an incidence of more than 1% of the population. In men older than 40 years, it is the most common inflammatory arthritis [1]. The gold standard for establishing a definite diagnosis of gout is the presence of intracellular crystals of monosodium urate (MSU) in aspirated joint fluid or of tophi [2]. However, even in clinical studies, gout is often not diagnosed by arthrocentesis. Therefore, already in the early 1960s, the first criteria for the classification of gout were proposed. These criteria included a serum urate (SU) level >7 mg/dl in men or >6 mg/dl in women, the presence of tophi, the presence of MSU crystals in synovial fluid or joint tissue, and one or more attacks of podagra characterized by painful joint swellings with abrupt onset and remission within 2 weeks [3]. During the last several decades, the routine use of allopurinol has reduced the occurrence of the clinical presentation of gout flares and the incidence of chronic gout, in particular [4], [5].
Nevertheless, gout, and even chronic gout, still occurs. Therefore, it would be highly desirable to confidently diagnose gout at an already early stage in order to prevent the destruction of joints caused by tophaceous gout. Often, clinical findings and even joint aspiration are inconclusive [6]. Thus, for the assessment of gout, further imaging modalities may be helpful, particularly in cases, where the disease is masked by co-occurring joint disease, such as psoriatic arthritis.
Imaging diagnosis mainly relies on radiography with characteristic signs of dense soft tissue swelling, joint effusions, and iuxtaarticular erosions [7], [8], [9]. Magnetic resonance imaging (MRI) with high gradient field strength and surface coils has also been shown to be useful in documenting erosions and tophaceous lesions with densely packed MSU crystal compositions in bones, tendons, and bursae [10].
Sonography (US) is an imaging technique that has attracted considerable interest in the field of rheumatology in recent years [11]. As a result of wide availability and technological improvements using high-resolution US, this technique has the potential to facilitate or confirm the diagnosis of gouty arthritis. Relevant information about the characteristic appearance of gouty manifestations in joints can be easily obtained with high-resolution US [12]. The disease activity characterized by increased intraarticular perfusion can be assessed with Power Doppler and therapeutic effects can be monitored.
In the literature, several reports have described the typical US appearance of gouty arthritis [13], [14], [15], [16], [17], [18]. However, these studies included very small study groups including less than six patients and did not compare the sonographic appearance to clinical and laboratory information or to conventional radiographic findings. In addition, these reports differed in their description of the sonographic appearance of tophaceus nodules and the overall presentation of gouty arthritis.
The aim of the present study was to explore the spectrum of sonographic appearance of acute and chronic forms of gouty arthritis in conjunction with radiographic, clinical, and laboratory findings and to investigate whether US can provide clues on gouty arthritis that adds to the information available from conventional radiography, clinical examination, and laboratory results.
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Patients
In a prospective cross-sectional study, 19 patients (17 men, two women) with a mean ± S.D. age of 57.3 ± 10 years (range, 35–81 years) were referred by the Rheumatology Department. Inclusion criteria were clinical symptoms and signs suggestive of gout according to the EULAR evidence based recommendations for gout [19]. Four patients with recently diagnosed gout by clinical symptoms and 15 patients with a history of long-standing gout were included. Chronic gout was diagnosed in 9 of 15 patients by
Patients
Twenty-one patients were referred with a suspected diagnosis of gout (18 men, 3 women; mean age, 57.3 years; range, 35–81 years; mean height, 174 ± 7.5 cm; mean weight, 80.7 ± 12.4 kg). After work-up, two of the patients (one woman, one man) were found to have rheumatoid arthritis (RA) and not gout, based on clinical and radiological features. We excluded these two patients from further evaluations. Clinical data from the remaining 19 patients are shown in Table 1. Six patients presented with an
Discussion
In its early manifestations, the typical clinical appearance of acute gout, with acute attacks occurring mainly during the night, its typical monoarticular localization in 85–90%, and involvement of the first MTP in over 50%, allows a reasonably accurate clinical diagnosis [9]. Although sometimes misleading, elevated serum urate levels may help to arrive at a diagnosis more quickly, and the presence of intracellular MSU crystals in aspirated joint fluid or tophus serves as confirmation. In
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