A 80-year-old man presents with two weeks of wrist swelling and pain. His exam reveals swelling and tenderness over the dorsum of his right wrist as well as synovial swelling of the second and third metacarpophalangeal joints of his left hand. His serum uric acid concentration is 6.0 mg/dL. The longitudinal and transverse images of the dorsal aspect of his right wrist are shown below. What is the MOST likely diagnosis?