Rice Bodies: Differential Diagnosis

Rice bodies, named for their macroscopic similarity to polished grains of rice, are made up of central acidophilic material surrounded by collagen and fibrin. Their etiology is debated. One theory suggests that they are due to small synovial infarctions that lead to shedding of synovium and subsequent encasement by fibrin. Another theory posits that rice bodies form independently in synovial fluid and enlarge by aggregation of fibrin.

Rice bodies are iso- or hypointense to skeletal muscle on T1- and T2-weighted images, and can be seen clearly against the background of fluid on T2-weighted images. They tend to blend in with fluid on T1-weighted images.

The image above from a young boy reveal distension of the extensor digitorum tendon sheath with multiple, punctate objects. The objects blend in with fluid signal on the T1-weighted image and are best seen against fluid on the T2-weighted image.

Differential considerations for rice bodies include:

• Infection: First described in the setting of tuberculous arthritis, rice bodies have also been reported with atypical mycobacteria and other infections.
• Chronic synovitis or bursitis: Most commonly seen in rheumatoid arthritis, where it typically presents as a painless mass. It can also be seen in juvenile idiopathic arthritis or in the absence of any underlying systemic disorder.
• Synovial chondromatosis: Can be difficult to differentiate from rice bodies. In general, rice bodies have low signal on both T1- and T2-weighted sequences, making them more visible on T2-weighted images. In contrast, synovial chondromatosis may be intermediate to high signal intensity on T1-weighted images and bright on T2-weighted images, making them more visible on T1-weighted sequences.

References

• Chau CL, Griffith JF, Chan PT, Lui TH, Yu KS, Ngai WK. Rice-body formation in atypical mycobacterial tenosynovitis and bursitis: findings on sonography and MR imaging. AJR Am J Roentgenol. 2003 May;180(5):1455-9.
• Chen A, Wong LY, Sheu CY, Chen BF.Distinguishing multiple rice body formation in chronic subacromial-subdeltoid bursitis from synovial chondromatosis. Skeletal Radiol. 2002 Feb;31(2):119-21.
• Cuomo A, Pirpiris M, Otsuka NY. Case report: biceps tenosynovial rice bodies. J Pediatr Orthop B. 2006 Nov;15(6):423-5.
• Martini G, Tregnaghi A, Bordin T, Visentin MT, Zulian F. Rice bodies imaging in juvenile idiopathic arthritis. J Rheumatol. 2003 Dec;30(12):2720-1.
• Popert AJ, Scott DL, Wainwright AC, Walton KW, Williamson N, Chapman JH. Frequency of occurrence, mode of development, and significance or rice bodies in rheumatoid joints. Ann Rheum Dis. 1982 Apr;41(2):109-17.