Gout is a crystal arthropathy due to deposition of monosodium urate (MSU) crystals in and around the joints.
Typically occurs in those above 40 years. There is a strong male predilection of 20:1.
Characterised by monosodium urate crystals deposition in periarticular soft tissues. The crystals are needle-shaped and are strongly birefringent in plane polarised light 10. The synovial fluid is generally a poor solvent for monosodium urate and therefore causes crystallisation at low temperatures. The crystals are chemotactic and activate complement.
There are five recognised stages of gout:
- asymptomatic hyperuricaemia
- acute gouty arthritis
- intercritical gout (between acute attacks)
- chronic tophaceous gout
- gouty nephropathy
- hyperuricaemia: only a small proportion of hyperuricaemic patients develop gout and often takes 20-30 years to develop
- alcohol intake
- myeloproliferative disorders
- Lesch-Nyhan syndrome
Usually has an asymmetrical polyarticular distribution:
- joints: 1st MTP joint most common (known as podagra when it involves this joint); hands and feet are also common
- less common: bones, tendon, bursa
Most radiographic findings include the skeletal system.
Characteristic radiologic changes occur in the chronic stage, though not all patients progress to this. There is a predilection for the small joints of the hands and feet. Chondrocalcinosis is present in ~5%.
- joint effusion (earliest sign)
- preservation of joint space until late stages of the disease
- absence of periarticular osteopenia
- eccentric erosions
- the typical appearance is the presence of well-defined “punched-out” erosions with sclerotic margins in a marginal and juxta-articular distribution, with overhanging edges (see case 12) also known as rat bite erosions
- punched-out lytic bone lesions
- overhanging sclerotic margins
- avascular necrosis
- mineralisation is normal
Surrounding soft tissues
- tophi: pathognomonic
- olecranon and prepatellar bursitis
- periarticular soft tissue swelling due to crystal deposition in tophi around the joints is common
- the soft tissue swelling may be hyperdense due to the crystals, and the tophi can calcify (uncommon in the absence of renal disease)
While there can be variation in appearance, tophi tend to be hyperechoic, heterogeneous, have poorly defined contours. They can be multiple grouped and surrounded by anechoic halos 8.
Findings generally reflect those on the plain radiograph.
Dual energy CT can distinguish between urate mineralisation and calcification, which may be useful for cases where the clinical and biochemical presentation is atypical11.
Signal characteristics of gouty tophi are usually:
- T1: isointense
- variable 4
- majority of lesions are characteristically heterogeneously hypointense
- T1 C+ (Gd): tophus often enhances
- 1. Dähnert W. Radiology review manual. Lippincott Williams & Wilkins. (2007) ISBN:0781738954. Read it at Google Books - Find it at Amazon
- 2. Carter JD, Kedar RP, Anderson SR et-al. An analysis of MRI and ultrasound imaging in patients with gout who have normal plain radiographs. Rheumatology (Oxford). 2009;48 (11): 1442-6. doi:10.1093/rheumatology/kep278 - Pubmed citation
- 3. Oaks J, Quarfordt SD, Metcalfe JK. MR features of vertebral tophaceous gout. AJR Am J Roentgenol. 2006;187 (6): W658-9. doi:10.2214/AJR.06.0661 - Pubmed citation
- 4. Yu JS, Chung C, Recht M et-al. MR imaging of tophaceous gout. AJR Am J Roentgenol. 1997;168 (2): 523-7. AJR Am J Roentgenol (abstract) - Pubmed citation
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- 6. Sheldon PJ, Forrester DM, Learch TJ. Imaging of intraarticular masses. Radiographics. 2005;25 (1): 105-19. doi:10.1148/rg.251045050 - Pubmed citation
- 7. Perez-Ruiz F, Dalbeth N, Urresola A et-al. Imaging of gout: findings and utility. Arthritis Res. Ther. 2009;11 (3): 232. doi:10.1186/ar2687 - Free text at pubmed - Pubmed citation
- 8. de Ávila Fernandes E, Kubota ES, Sandim GB et-al. Ultrasound features of tophi in chronic tophaceous gout. Skeletal Radiol. 2011;40 (3): 309-15. doi:10.1007/s00256-010-1008-z - Pubmed citation
- 9. Chowalloor PV, Siew TK, Keen HI. Imaging in gout: A review of the recent developments. Ther Adv Musculoskelet Dis. 2014;6 (4): 131-43. doi:10.1177/1759720X14542960 - Free text at pubmed - Pubmed citation
- 10. Ivorra J, Rosas J, Pascual E. Most calcium pyrophosphate crystals appear as non-birefringent. Ann. Rheum. Dis. 1999;58 (9): 582-4. doi:10.1136/ard.58.9.582 - Free text at pubmed - Pubmed citation
- 11. Desai MA, Peterson JJ, Garner HW, Kransdorf MJ. Clinical utility of dual-energy CT for evaluation of tophaceous gout. Radiographics : a review publication of the Radiological Society of North America, Inc. 31 (5): 1365-75; discussion 1376-7. doi:10.1148/rg.315115510 - Pubmed
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