Gout Imaging in Care Save

Gout is all about the crystals and the consequences of the disease are due to the inflammation they cause. Getting rid of urate crystals is the ultimate goal in gout, as we now know that it leads to the risk zero of flares and it normalizes the cardiovascular risk level of patients with gout. Yet, the current follow-up marker in daily practice is still blood serum urate levels, which provides an idea of if the management is heading in the right direction, but does not inform on what is the current crystal burden in joints. 

This is where imaging comes in.

Conventional radiography had been the only available imaging techniques in gout for decades. Trouble is that radiography can’t see urate crystals and signs of gout are visible when the damage is done. Fortunately, more advanced imaging techniques have been studied during the past 15 years, and have now proven to be very useful for clinical practice. These techniques are ultrasound and dual-energy computed tomography (DECT). Ultrasound has been successfully applied to the study of joints in inflammatory rheumatic diseases such as rheumatoid arthritis to measure active inflammation. In gout, an additional use for ultrasound is that crystal deposits have a unique echogenic appearance both on top of the cartilage (known as the ‘double contour sign’) and small tophaceous deposits undetected by clinical examination can be seen. DECT is now a widely available computed tomography which uses not one but two x-ray beams of different energies (hence the name). This technique provides an assessment of the biochemical composition of the observed bodily structures, and in particular is capable of differentiating chemically urate crystal deposits from soft tissue and bone.

In clinical care, these techniques now have a clear role in the diagnosis and management of gout, as now acknowledged in European recommendations(1). For the diagnosis, the two techniques proved to be extremely useful to identify urate crystals deposited in and outside joints, which is now considered sufficient to confirm the diagnosis of gout, even without microscopic confirmation after junct puncture. All of this without needing to stick a needle into anybody. Another fundamental role of ultrasound and DECT is to measure the crystal burden which is predictive of upcoming flares but also of cardiovascular comorbidities and even mortality. The techniques are now used to monitor the dissolution of these deposits, helping to guide how long prophylaxis with anti-inflammatory treatments are still needed and if urate lowering is sufficient.

Above all, ultrasound and DECT tells us when the battle against crystals is won.

1. Mandl, P., M. A. D'Agostino, V. Navarro-Compan, et al. 2023 EULAR recommendations on imaging in diagnosis and management of crystal-induced arthropathies in clinical practice. Ann Rheum Dis 2024;83: 752-759.