Gout is the most prevalent arthritis worldwide. It is caused by monosodium urate (MSU) crystal deposits in articular and extra-articular structures, due to the increased levels of uric acid in serum in excess of saturation levels.1 The gold standard diagnostic technique for gout continues to be the detection of MSU crystals in synovial fluid2 although in the latest ACR/EULAR diagnostic classification criteria dual-energy computed tomography (DECT) has been included along with ultrasonography as accepted diagnostic techniques.3,4 These provide more precise information regarding the course of the disease, since on many occasions the extent of MSU deposits is greater than expected, affecting clinically non-apparent joints.5

The aim of our study was to use ultrasound to assess the effects on joints in those patients included in the study whose disease was badly controlled clinically despite hyperuricaemia treatment. To do so, the level of crystal deposits and ultrasound compromise were studied, together with the uricaemia level. This was an observational cross-sectional study with 115 patients diagnosed with gout in keeping with the ACR6 criteria of a multi hospital group which took place between December 2013 and May 2017. The ultrasound test was performed according to the Peiteado et al.7 protocol which determined the number of joints with signs of gout (double contour sign, aggregates and/or tophi) and signs of acute activity through Doppler indication. Variables such as age, sex, high blood pressure, diabetes, chronic kidney disease and the evolution of the disease over time were also included.

One hundred and fifteen patients (112 men and 3 women) with a mean age of 57±13 years and a mean disease evolution of 14±10 years took part. All of them had poor clinical disease control with single joint compromise. Ultrasound compromise observed was: 47 patients (40.86%) with Doppler presence, 90 with aggregates and/or tophi (78.26%) and 53 with double contour sign (42.08%). The uricaemia mean was 7.4mg/dl. Out of the 115 patients studied, 94 presented with levels of uric acid above 6mg/dl, of which an extensive joint compromise was observed in 76.59%. The remaining 21 patients presented with uric acid levels below 6mg/dl, of whom 18 had extensive ultrasound compromise (85.71%). The correlation between uricaemia and ultrasound compromise was not statistically significant (OR=.3; .6–1.1) As a result, in this study we observed that the patients with uricaemia which was within the therapeutic objective (<6mg/dl) presented with a greater degree of ultrasound compromise than was expected.

Once gout has been diagnosed, follow-up is usually clinical and analytical, aimed at maintaining urate levels within the recommended objective in national and international guidelines. However, even reaching optimum uricaemia levels, MSU crystal deposits may continue to be present in the joint.8 For this reason we could consider ultrasound as a key tool in the follow-up of those patients whose uricaemia levels fall within therapeutic objective levels, but where clinical activity is still persistent. This technique allows us to correctly determine the extent of the deposits and joint compromise in the gout, which may support the decision to change or intensify treatment, to promote crystals dissolution and disappearance of subclinical inflammation.9,10 It is also an accessible and innocuous technique for quick, non-invasive assessment of the magnitude and extension of the disease, leading to further information than standard physical examination.