The advanced imaging of gouty tophi.

Gout is a metabolic disorder in which there is hyperuricemia caused by an increase in production or a decrease in excretion of uric acid. Long-lasting hyperuricemia causes the deposition of monosodium urate crystals in the joints and soft tissues, triggering gouty arthritis and, if not properly treated, the formation of gouty tophi. The diagnosis of gout is usually based on clinical presentation and laboratory examinations, long before any abnormality can be demonstrated with imaging. Radiography is the primary imaging modality used in the initial evaluation of gouty arthritis. Ultrasonography, CT, MRI, and nuclear medicine are seldom necessary. Occasionally a tophus has an unusual presentation and simulates neoplasm or infection prompting the utilization of cross-sectional imaging for further evaluation and surgical planning. Cross-sectional imaging is also used in areas that are difficult to visualize on radiographs such as spine, sacroiliac joints, and soft tissues.