VIZCAYA, Spain—Advances in ultrasonography (US), magnetic resonance imaging (MRI), and computed tomography (CT) show promise for improving clinical detection of and understanding of gout, but the large proportion of gout patients who do not receive urate-lowering therapy remains the major clinical issue, experts report. In a wide-ranging review of imaging in Current Opinion in Rheumatology,¹ Fernando Perez-Ruiz, MD, and Esperanza Naredo, MD, conclude that US, CT, and MRI may improve both the evaluation of tophi not revealed in clinical examination or simple radiographs and the monitoring of urate deposition.

"This would be of outstanding interest for clinical trials, but also for evaluating clinical response to urate-lowering therapy," write Dr. Perez-Ruiz, with the department of rheumatology at Hospital de Cruces, in Vizcaya, Spain, and Dr. Naredo, with the department of rheumatology at Hospital Severo Ochoa, in Madrid, Spain.

Undertreatment still main problem in gout

However, gout expert Philip Conaghan, MB, PhD, FRACP, FRCP, professor of musculoskeletal medicine at the University of Leeds, in the United Kingdom, told CIAOMed that the more important clinical issue is not the picture but the prescribing.

"The overriding current message is not an imaging one! It is that gout is largely undertreated with hypouricemic agents, and uric acid levels are not lowered sufficiently in many patients," Dr. Conaghan said. "Currently, imaging with conventional radiographs plays very little role in gout management except to confirm secondary joint damage. While waiting for such damage to occur is not optimal therapy, sometimes this [radiographic evidence] may help convince a patient to initiate or increase hypouricemic therapy. So, evidence permitting, using modern imaging may increase patient and physician understanding of the extent of this disease and improve therapy."

US and MRI promising but need more validation

Perez-Ruiz and Naredo point out that "to date no imaging technique has been reported to be able to substitute for polarized compensated microscopy diagnosis" in gout, but note that the widespread availability of portable US is likely to improve evaluation and differentiation of subcutaneous nodules, in part through US-guided nodule aspiration of suspect lesions and synovial fluid. They also point to the "double contour" US sign as potentially useful. "This ultrasonography sign is observed as hyperechoic thickening of the cartilage superficial margin, which appeared as thick as the deeper margin, and was distinct from the normal interface reflex and from central hyperechoic foci seen in chondrocalcinosis," they write.

Dr. Conaghan is similarly optimistic about the prospects of US and MRI. "Ultrasound is clearly the most promising since it is useful in the clinic during the patient visit and can be also used to guide joint aspiration and injection," he said. "The advantage of US and MRI is that they demonstrate soft tissue abnormalities which cannot be seen on radiographs."

According to Perez-Ruiz and Naredo, preliminary evidence suggests that power-Doppler US can differentiate active from inactive, noninflamed fibrotic synovial tissue and might provide a way to monitor acute gouty attacks. "[T]he power-Doppler signal was even present in symptomatic joints from gouty patients that were previously symptomatic," they write. They would like to see studies that use power-Doppler US to examine changes in gouty joints after colchicine, NSAIDs, and chronic urate-lowering therapy.

Validation of these approaches remains incomplete, however. Dr. Conaghan said that the most important unanswered questions are whether US or MRI can usefully aid in gout diagnosis, and whether the detection of subclinical urate deposition (not apparent on routine examination) is important for prognosis and lead to more aggressive hypouricemic therapy.

Reference

1. Perez-Ruiz F, Naredo E. Imaging modalities and monitoring measures of gout. Curr Opin Rheumatol. 2007;19:128-133.