HSS Ultrasound Case 86

Clinical History 56 yo male with known osteoarthritis of the metatarsophalangeal (MTP) joint of the great toe presented with acute pain and swelling over the medial side of the great toe.

Ultrasound evaluation was requested.

Ultrasound of the Month – Case 86

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Ultrasound-guided aspiration of the joint was performed, which revealed negatively birefringent crystals

Diagnosis: Gout Discussion: Gout is a crystal deposition disease in which tophi made up of monosodium urate form in soft tissues, including within joints, and incite an inflammatory arthritis.

Elevation of serum uric acid is suggestive, but a definitive diagnosis requires the identification of negatively birefringent monosodium urate crystals in the affected site.

Ultrasound is a cost-effective imaging modality for assessing a joint that could potentially be affected by an inflammatory arthritis.

Ultrasound also has the advantage of allowing guided arthrocentesis.

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Discussion Continued: On ultrasound, the classic features of a joint affected with gout include: • hyperechoic mass-like intraarticular deposits reflecting tophaceous material • a layer of hyperechoic material lining the articular cartilage, referred to as the “double contour sign”, representing uric acid crystals • Accompanying synovitis (joint effusion with synovial hyperemia).

Double contour sign, from Thiele RG, Schlesinger N. Diagnosis of gout by ultrasound. Rheumatology 2007;46:1116-1121

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