Table 1: Common pathological findings of gout.

Erosions
Juxta-articular cortical irregularity and depression overhanging edge sclerotic margins
Findings seen in at least two planes
Erosions adjacent to tophus (causative agent)
CT is most sensitive. US can overestimate

Synovial proliferation
Synovial thickening enhancement on post contrast images increased vascularity on Doppler imaging
Both US and MRI are very sensitive
Vascularity may not be obvious when patient is on treatment/NSAID
Synovial proliferation gout RA, needs more research

Tophus
Eccentric high-density soft tissue swelling from chronic granulomatous response to MSU crystals
Can be intra- or extra-articular
Characteristic US appearance: hypoechoic peripheral rim/halo and hyperechoic/heterogeneous center
Can also be imaged by radiograph, DECT, CT, and MRI
Calcification in the tophus suggests renal impairment

Bone marrow edema
Uncommon/minimal, specifically centered around erosion
If extensive, think of inflammatory arthritis or infection, whether associated with the underlying diagnosis or not
Only MRI can demonstrate bone marrow edema

Cartilage involvement
MSU crystals deposit on articular cartilage surface (anechoic curvilinear band paralleling the cortex) giving “double contour sign”
Hydroxyapatite deposition is within cartilage substance US is most sensitive

Joint effusion
Anechoic fluid in the joint recess/space not specific sign unless accompanied by small numerous hyperechoic foci “snow storm appearance”
Aspirate to confirm gout and exclude infection