Gout is a crystal arthropathy due to deposition of monosodium urate crystals in and around the joints.
Typically occurs in those above 40 years. There is a strong male predilection of 20 to 1.
Characterised by monosodium urate crystals (negatively birefringent) deposition in periarticular soft tissues. The synovial fluid is generally a poor solvent for monosodium urate and therefore causes crystallisation at low temperatures.
The crystals are chemotactic and activate compliment.
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 hyper uricaemic 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 ; hands and feet are also common.
- less common : bones, tendon, bursa.
Most radiographic findings involve 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 disease
- absence of periarticular osteopaenia.
- 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.
- punched out lytic bone lesions
- overhanging sclerotic margins
- avascular necrosis
- mineralisation is normal
Surrounding soft tissues
- tophi : pathognomonic
- 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 absence of renal disease).
Signal characteristics of gouty tophi are usually
- T1 : iso intense
- T2 : variable 4 with the majority of lesions being heterogeneously hypointense
- T1 C+ (Gd) : the tophus usually enhances
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- 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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