Radiologic Evidence of Symmetric and Polyarticular Monosodium Urate Crystal Deposition in Gout – A Cluster Pattern Analysis of Dual-energy CT

OBJECTIVES:

To determine the clustering patterns of monosodium urate (MSU) crystal deposition and bone erosions among patients with gout requiring urate-lowering therapy (ULT) using dual-energy CT (DECT).

METHODS:

DECT scans of bilateral hands/wrists, feet/ankles, and knees were obtained on 153 patients with gout on allopurinol ≥300 mg daily for ≥3 months. Two radiologists assessed the images at pre-specified sites (15 in the hands/wrists, 12 in the feet/ankles, 4 in the knees). Clustering patterns of MSU crystal deposition and bone erosions were evaluated.

RESULTS:

Among 153 patients with gout (mean duration, 15 years) on allopurinol (mean duration, 5 years), MSU crystal deposition (67%) affected multiple sites in the hands/wrists, feet/ankles, and knees more often than would be expected by chance (p<0.001 for all 3 regions). In the feet/ankles, bone erosions were also observed in a clustered manner (p<0.001). Presence of MSU crystal deposition at a particular joint was most strongly associated with symmetric involvement of the same joint of the opposite extremity in the hands/wrists, feet/ankles, and knees (adjusted odds ratio (OR) 26.1, 46.9, and 9.9, respectively). Similarly, presence of erosions in the feet/ankles was highly symmetric (adjusted OR 91.4). Erosions were 8-fold more likely to be present in sites with MSU crystal deposition compared to those without.

CONCLUSION:

Among patients with longstanding gout on ULT, MSU crystal deposition and bone erosions affect multiple joints within the hands/wrists, feet/ankles, and knees in a highly symmetric manner. These radiologic data support the notion of MSU crystal deposition in gout as a symmetric polyarthropathy.