Relationship between Urate Crystal Deposits Detected by Dual-energy Computed Tomography and Bone Erosions in Symptomatic Gout Patients without Clinically Apparent Tophi

Objective. Dual-energy computed tomography (DECT) allows sensitive detection of monosodium urate (MSU) crystal deposits in gout. However, the role of MSU deposits on DECT during the disease process of gout is not clear. The aim of our study was to evaluate the relationship between joint damage and MSU deposits detected by DECT in symptomatic non-tophaceous gout. Methods. DECT scans of 51 gout patients without clinically apparent tophi were assessed. Individual ankle and foot joints and Achilles tendon insertion sites were evaluated for the presence of MSU deposits and bone erosions. The total volume of MSU crystal on DECT was quantified using an automated software program. Clinical and laboratory data at the time of the DECT evaluation were obtained from medical record. Results. MSU deposits were detected in 92.2% of the patients evaluated. Median number and total volume of MSU deposit per patient was 5.0 and 0.6 cm³, respectively. Bone erosion was found in 54.9% of patients. MSU deposits in the first (1st) metatarsophalangeal (MTP) joints were significantly associated with presence of bone erosions (odds ratio [OR] 3.77, 95% confidence interval [CI] 1.06∼13.38, p=0.040). Older age and frequent gout attack were associated with development of bone erosion in patients with MSU deposits (OR 1.12 and 2.57, 95% CI 1.04∼1.22 and 1.02∼ 6.50, p-value 0.004 and 0.047, respectively). Conclusion. MSU deposits and erosions were frequently detected by DECT in symptomatic non-tophaceous gout patients, and MSU deposits in 1st MTP joints were associated with presence of bone erosions especially in patients with older age and frequent gout attack.