Musculoskeletal ImagingGout
a metabolic disease involving defective purine metabolism, which is characterized by
hyperuricaemia with or without a recurrent acute inflammatory arthritis and tophaceous deposits of monosodium urate crystals intra- and periarticularly. Gout may be primary (idopathic) or secondary. Manifestations include an asymmetric polyarticular involvement of the feet, hands, wrists, elbows and knees.
Idiopathic gout may be divided into several stages: an early asymptomatic stage with hyperuricaemia; acute gouty arthritis, especially involving the joints of the lower extremity; an asymptomatic interval phase between attacks of gout; and chronic tophaceous gout, marked by deposition of urate crystals, which collect in the subchondral areas of bone (or more deeply) and lead to cystic defects and erosive osseous changes. An inflammatory pannus may also develop. Larger tophi may calcify (Fig.1) or ossify and lead to rupture of tendons, nerve compression and paralysis.
Radiographic manifestations (Table 1) generally occur late in the course of the disease. In acute arthritic attacks, transient soft tissue swelling may occur surrounding involved joints. Other changes include intra-articular and extra-articular bone erosions, relative preservation of the joint space, subperiosteal apposition of bone, intraosseous calcification, and secondary degenerative alterations.
Gout, Table 1. Radiographic features of gout.
| Asymmetrical joint involvement |
| Eccentric soft tissue swelling |
| Occasional soft tissue calcification |
| Absent or mild osteoporosis |
| Joint space loss frequently absent |
| Eccentric intra- and extra-articular bone erosions, frequently with sclerotic margin and overhanging edge sign |
| Rare, malalignment, subluxation |
Common sites of involvement include the foot (particularly the metatarsophalangeal joint), hand, wrist elbow and knee; the shoulder, hip, sacroiliac joint and spine are affected less frequently. In the foot, hallux valgus deformity may be present. The hands and wrists show widespread joint abnormalities but lack the symmetry found in rheumatoid arthritis.
MR imaging, which reveals the extent of soft tissue, synovial, cartilaginous and osseous involvement, may be useful in assessing the full extent of gout.
Gout may coexist with other disorders, such as calcium pyrophosphate dihydrate crystal deposition disease, osteoarthritis and rarely rheumatoid arthritis or joint infection.
Special types of gout also exist: an early onset idiopathic gouty arthritis, gout associated with type I glycogen storage disease type 1, Lesch Nyhan syndrome and saturnine gout.
DR/RB