The identification of urate crystals in the aspirate is diagnostic of gout. If urate crystals are not seen in the aspirate; however, this does not necessarily exclude gout. Up to 16% patients diagnosed with acute gout can have negative aspirates [56]. MRI Area of Interest Without and With IV Contrast MRI can show the presence of tophi, crystal induced synovitis, and joint damage [57]; however, the 2018 EULAR recommendations state that MRI has limited utility for diagnosis of gout compared with US and DECT. MRI with or without IV contrast is not supported for routine evaluation of gout in the extremities following initial radiographs [55]. MRI Area of Interest Without IV Contrast MRI can show the presence of tophi, crystal induced synovitis, and joint damage [57]; however, the 2018 EULAR recommendations state that MRI has limited utility for diagnosis of gout compared with US and DECT. MRI without IV contrast is not supported for routine evaluation of gout in the extremities following initial radiographs [55]. US Area of Interest The 2018 EULAR recommendations favor US over other modalities [55]. The Outcome Measures in Rheumatology definitions of US elementary lesions in gout include double contour sign, tophus, aggregates, and erosions [58]. Identification of the double contour sign and soft tissue tophi are highly sensitive, specific, and accurate for the diagnosis of gout [59,60], with double contour sign having excellent reliability [61]. US has been shown to outperform clinical assessment in the diagnosis of gout [50] and outperforms radiography in the detection of erosions, although limitations exist if an erosion involves an area of bone that is inaccessible to US evaluation [62]. There is evidence that US may have higher sensitivity for detection of gout compared with DECT in early gout (duration <1 year) [63].
Chronic Extremity Joint Pain Suspected Inflammatory Arthritis Crystalline Arthritis or Erosive Osteoarthritis PCAs. The identification of urate crystals in the aspirate is diagnostic of gout. If urate crystals are not seen in the aspirate; however, this does not necessarily exclude gout. Up to 16% patients diagnosed with acute gout can have negative aspirates [56]. MRI Area of Interest Without and With IV Contrast MRI can show the presence of tophi, crystal induced synovitis, and joint damage [57]; however, the 2018 EULAR recommendations state that MRI has limited utility for diagnosis of gout compared with US and DECT. MRI with or without IV contrast is not supported for routine evaluation of gout in the extremities following initial radiographs [55]. MRI Area of Interest Without IV Contrast MRI can show the presence of tophi, crystal induced synovitis, and joint damage [57]; however, the 2018 EULAR recommendations state that MRI has limited utility for diagnosis of gout compared with US and DECT. MRI without IV contrast is not supported for routine evaluation of gout in the extremities following initial radiographs [55]. US Area of Interest The 2018 EULAR recommendations favor US over other modalities [55]. The Outcome Measures in Rheumatology definitions of US elementary lesions in gout include double contour sign, tophus, aggregates, and erosions [58]. Identification of the double contour sign and soft tissue tophi are highly sensitive, specific, and accurate for the diagnosis of gout [59,60], with double contour sign having excellent reliability [61]. US has been shown to outperform clinical assessment in the diagnosis of gout [50] and outperforms radiography in the detection of erosions, although limitations exist if an erosion involves an area of bone that is inaccessible to US evaluation [62]. There is evidence that US may have higher sensitivity for detection of gout compared with DECT in early gout (duration <1 year) [63].