Background/Purpose: urate intra-articular deposits are seen in ultrasound as double contour sign (DCS), and hyperechogenic aggregates and tophi, but the extent of contribution of any of these findings to synovial inflammation has yet to be determined. Only tophi have been shown to date sensitivity to change during urate-lowering therapy.

Methods: to evaluate the association between DCS and tophi with the presence of synovial inflammation in ultrasound examination, patients with crystal-proven gout were recruited from two cohorts of prospective follow-up, one on active treatment and the other after withdrawal of urate-lowering therapy, were to be consecutively included. They had to be asymptomatic (no flare, no chronic swelling) for at least 4 years, not on colchicine, NSAID, corticosteroids, or IL-blockers. Ultrasonography of the first metatarsophalangeal joint (1st MTP) and of the non-dominant knee was performed by an skilled explorer who was blinded for clinical data. The DCS was predefined as absent or present and in in less or more than 50% of the synovial surface. In the knee joint, the DCS location was also assessed as present in one or both femoral condyles. The presence of tophi was evaluated as hyperechogenic conglomerates of at least 5mm in maximum diameter, with a hypoechogenic halo associated. Synovial inflammation was evaluated by the measurement of synovial thickening with a semi-quantitative scale (0-3) and Power-Doppler (PD) with a semiquantitative scale (0-3). Bi-variable and multiple regression analysis were performed.

Results: ultrasonopgraphy was proposed to 100 consecutive patients who fulfilled criteria, of which 88 agreed and attended the appointment. All of them were male, with a median age of 57 ± 9 years, 74% with previous involvement of 1st MTP joint and 59% of the examined knee. Thirteen patients were excluded from analysis due to the presence of ultrasonographic chondrocalcinosis in the knee. The frequency of deposits in both cohorts was not different, a pooled analysis therefore being conducted. The descriptive findings are presented in the table:

Multiple regression analysis showed that the presence of synovitis >0 was only statistically associated in the 1st MTP to tophi (R² 0.31), and in the knee to the presence of extense or bilateral DCS and tophi (R² 0.28). The PD>0 signal was only associated in both 1st MTP and in knee to tophi (R² 0.25 and 0.18, respectively). The more restrictive analysis of synovitis>1 and PD>1 did not show changes in the results, although numbers were small.

Conclusion: ultrasonographic urate deposits, as tophi or extense double contour) are associated to synovitis or active synovitis (intra-articular synovitis with PD signal) as markers of synovial inflammation. The presence of tophi is the main factor associated, so the resolution of the intra-articular tophi seems to be the principal therapeutic goal for urate-lowering therapy.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/relationship-between-ultrasonographic-synovial-inflammation-and-ultrasonographic-urate-deposition-findings-in-patients-with-gout/